Water Current Meters 

IN THE SMITHSONIAN COLLECTIONS OF THE 

NATIONAL MUSEUM OF HISTORY AND TECHNOLOGY 

Arthur H. Crazier 

SMITHSONIA N INSTITUTIO N 

SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY / NUMBER 28 

Water Current Meters 

IN THE SMITHSONIAN COLLECTIONS OF THE 

NATIONAL MUSEUM OF HISTORY AND TECHNOLOGY 

Arthur H. Crazier 

ISSUED 

EEC 3 0 1974 

SMITHSONIAN INSTITUTION PRESS 

City of Washington 

1974 
ABSTRAC T 

Frazier, Arthur H. Water Current Meters in the Smithsonian Collections of the 

National Museum of History and Technology. Smithsonian Studies in History and 

Technology, number 28, 95 pages, 94 figures, 1974.—Water current meters are the 

basic instruments used in connection with stream gaging, the art of measuring and 

maintaining a continuous record of the volume, in cubic feet (or cubic meters) per 

second, of water flowing in rivers. The history of both that art and these instruments 

forms a large part of this study. The contributions of men like Marcus Vitruvius, 

Hero of Alexandria, Leonardo da Vinci, Benedetto Castelli, Sir Isaac Newton, and a 

large group of eminent modern hydrographers are discussed. 

Special attention is given to the type of current meters built for use on rivers 

such as those in the collection of the Smithsonian Institution. It does not include 

meters of the type featured in the collection at the Institut Oceanographique, Musee 

de Monaco, most of which were developed especially for measuring ocean currents. 

Whenever possible, the men responsible for introducing each new design are also 

discussed. 

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 4968. 

Library of Congress Cataloging in Publication Data 

Frazier, Arthur H. 

Water current meters in the Smithsonian collections of the National Museum of History and 

Technology. 

(Smithsonian studies in history and technology, no. 28.) 

Supt. of Docs, no.: SI 1.28:28. 

Bibliography: p. 

1. Water current meters—History. 2. U. S. Museum of History and Technology. I. Title. 

II. Series. Smithsonian Institution. Smithsonian studies in history and technology, no. 28. 

TC175.F76 551.4'83'028 74-5425 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price $2.05 

Stock Number 4701-00116 
Preface 

There has always been a close and cordial relationship between the Geological 

Survey and the Smithsonian Institution. Clarence King, the Survey's first director 

(1879-1881), received Smithsonian aid for his famous U.S. Geological Exploration of the Fortieth Parallel—the first systematic reconnaissance of that vast unmapped area of this country between the 105th and 120th meridian. John Wesley 

Powell, the Survey's second director, whose two trips through the Colorado Canyon 

brought him everlasting fame, conducted several investigations between 1871 and 

1874 with funds from Congressional appropriations stipulating that the work be 

performed "under the direction of the Smithsonian Institution." After those (and 

later) investigations were completed, the Smithsonian Institution established a 

Bureau of American Ethnology, with Powell in charge thereof. Just one year later, 

he assumed the directorship of the Geological Survey and for many years handled 

both positions at his office in the Smithsonian Institution building. The third director 

of the Geological Survey was Charles Doolittle Walcott who, after serving from 1894 

to 1907 as director of the Survey, became the Secretary of the Smithsonian, a position 

which he held until his death in 1927. For about one year before receiving the 

Smithsonian appointment, he divided his time between those two organizations, 

serving then as the Acting Assistant Secretary of the Smithsonian in Charge of the 

National Museum. 

Much of the information in this study was made available to the writer while 

employed in the Water Resources Division of the United States Geological Survey, 

an organization where current meters are as essential to its field engineers as a trowel 

is to a mason, or a plow is to a farmer. To the late Nathan C. Grover, Carl G. Paulsen, and John C. Hoyt, and to many of those others still living who guided my work in 

that agency and who encouraged my desire to delve into the history of current meters 

and stream-gaging methods, I am deeply grateful. 

John Clayton Hoyt (1874-1946) was employed by the Geological Survey in 

1902, and served that agency until his retirement in 1944. During parts of those 

42 years, he held the positions of Assistant Chief Hydrographer and Chief, Surface 

Water Division. Among his many interests was the improvement of current meters 

and the preservation of many of the early models. His early association with Walcott 

was conceivably a major influence in his having transferred several of those early 

meters (as soon as they achieved historical significance) to the Smithsonian Institution. Among them were several of the meters that had been used in the late 1880s 

by the U.S. Irrigation Survey, and the original models of both the Large and the 

Small Price current meters, which form the very foundation of the Smithsonian's 

fine collection. For John Hoyt's personal friendship and shining example, I have a 

deep sense of gratitude. 

I also wish to express my gratitude for the help given me by staff members of 

the Library of Congress, the Library of the universities of Wisconsin, Ohio State, and 

especially Iowa State, the latter of which houses the fine "HHT " collection sponsored by Dr. Hunter Rouse, who provided much valuable data for this study. 

For much of the information regarding the early stream-gaging activities in 

foreign lands, I am particularly indebted to the late Professor Steponas Kolupaila 

of Notre Dame University, and to Dr. Carlo Zammattio of Trieste, Italy. For much 

iii 
of the information regarding William Gunn Price and the early Price current meters, 

I am equally indebted to his own grandson, W. G. Price of New Cuyama, California, 

and to the late Charles E. Smart who, for many years had been Chairman of the 

Board in the W. & L. E. Gurley firm of Troy, New York. 

My sincere thanks are due to present members of the staff of the National Museum of History and Technology, Smithsonian Institution, in which the current meter 

collection is presently housed, and especially to its former director, Robert P. Multhauf, who encouraged me to undertake this study; to Jack Goodwin and Charles 

Berger of the museum's library, who helped me locate many of the books for which 

I felt a need; to George Norton, who arranged that I be furnished with photographs 

of the meters in the collection; and finally to Jon Eklund, who helped in so many 

ways while I was preparing this study. 

IV 
Contents 

Page 

Preface . . . ... . . iii 

Introduction .. . .. . . . 1 

Ancient Concepts .. . 2 

Emergence of Modern Hydrometric Methods . . . . . . . 6 

Q = A vs Q = AV .. . . . 6 

Free Floats ... . .. . ... . 8 

Tethered Floats . .. . .. . .1 5 

Paddles . .. . . . 18 

Paddle Wheels . . 21 

European Contributions ... . . 22 

American Innovations. 28 

Tubing Applications . 33 

The Pitot Tube ... . 33 

The Bentzel Velocity Tube . .. . . .3 5 

The Venturi Tube . ... . . . • . . . 37 

The Longitude Contest .. . .. . .. . 41 

De Saumarez' Ships' Logs ... . . 41 

The Log with a Vertical Axis . . . .. . . . .4 1 

The Log with a Horizontal Axis . 43 

Administrative Strategy, 1716 Style .... . 46 

Horizontal-Axis Meters . ... . . .. . 48 

Early European Developments . ... . 48 

Robert Hooke 48 

Reinhard Woltman . . ..... . . . 49 

Julien John Revy .... . . .5 0 

Joseph Saxton . .. . .5 1 

The Baumgarten Meter . 56 

Other American Models . . 63 

Hall's Current Meters .6 3 

The Haskell Current Meter .... . . .. . 64 

U.S. Irrigation Survey Models . . .. . 66 

Other European Developments 67 

.Moore's Current Meter . .. . • . .. . .6 7 

The Firm of A. Ott 68 

Steponas Kolupaila . . . 69 

Vertical-Axis Meters ... . . . . . 72 

The Henry Meter • . 73 

The Ellis Meters . . 74 

The Nettleton Meter 75 

The Price Meters 78 

Notes .8 7 

Literature Cited .. . .. . 88 

[ndex . ... . .. . 92 

Water Current Meters 

Arthur H. Jrazier 

INTRODUCTIO N 

A primary purpose of this study is to present a 

catalog of the water current meters in the Smithsonian Institution's National Museum of History and 

Technology, the largest collection of its kind in the 

world. It is also intended to present background information that will provide the reader with an understanding of where each current meter in the collection (and its designer) fits into the general historical 

setting relative to such instruments. The illustrations 

of current meters, for which accession numbers 

(NMHT) are noted, represent the present collection 

of such instruments in the Smithsonian Institution. 

Water current meters (referred to hereafter as 

"current meters" or simply "meters") are instruments 

used for evaluating the amount and velocity of water 

at one or more points in a flowing stream at any 

particular moment in time. The amount of water is 

measured in cubic feet per second, whereas the velocity is determined in feet per second. 

In America, the United States Geological Survey 

publishes in its Water-Supply Papers, the daily averages of the flow at almost 9000 "gaging stations" 

throughout all of the States. The following are just 

a few of the important uses made of such streamflow 

records: 

DAMS.—Dams are built for water-supply purposes, 

hydroelectric power, flood control, irrigation, navigation improvement, recreation lakes, and a host of 

other purposes. In each instance, a careful study of 

all pertinent streamflow records must be made well 

Arthur H. Frazier, 3636 Sixteenth Street, N. W'., Washing-

:on, D.C. 20010. Honorary Research Associate, Smithsonian 

Institution. 

in advance of any construction work to determine 

whether the drainage area above the selected site 

would yield a sufficient amount of water to accomplish the purpose for which the dam is intended, and 

to determine the amount of water that is likely to 

flow there under the maximum flood conditions. Inadequate spillway capacities constitute the major 

causes of dam failures. Therefore, a vital requirement 

in the design of any proposed dam is that its spillway 

capacity will be adequate to accommodate the largest 

probable flood. 

LITIGATIONS.—Litigations involving uses of water 

have occurred ever since the advent of written history. 

In A History of Technology edited by Charles A. Singer, et al., one finds that the words "rivers" and "rivals" stem from the same source. "That very word 'rivals' in Roman law denoted those who shared the 

water of a rivus, or irrigating channel; it thus implies 

jealously guarded rights and frequent quarrels."

 1 

In modern societies, perhaps the most equitable 

method yet devised for settling such disputes has been 

by means of court decisions that allot certain amounts 

or proportions of the available water to each litigant 

who has a legitimate right to it. Water masters are 

appointed to carry out these court orders. In almost 

all instances the masters base the distribution on discharge data procured through the use of current 

meters. Thus again we see that the reliable evaluation 

of discharge data is essential. 

PUBLIC HEALTH.—Today streams are often polluted by untreated sewage, manufacturing wastes, 

modern detergents, and dangerous chemicals, with a 

consequent destruction of fish and wild life. A large 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

percentage of attractive recreational waters and city 

water supplies have consequently been withdrawn 

from public use. Conservation officials and public 

health officials at all levels of government are deeply 

concerned about those conditions, particularly during 

periods of drought, when streams are low and the consequent percentage of pollution is exceptionally high. 

Streamflow records indicating the approach, arrival, 

intensity, and passage of these periods provide important information on which such officials can make 

appropriate administrative decisions. 

HIGHWAY BRIDGES AND CULVERTS.—The intelligent design of bridges and culverts for the vast network of highways across the nation depends on the 

availability and adequacy of streamflow records. 

Without such records, these structures might be built 

too large, resulting in excessive cost, or too small, 

thereby endangering the road in times of severe floods. 

Although this list could be greatly expanded, these 

examples are sufficient to indicate the importance of 

such records in relation to modern engineering and 

humanitarian problems.2 

ANCIENT CONCEPTS 

Although legends and archeological investigations 

have extended our knowledge of man's involvement 

with flowing water farther into the past than has 

written history, only two written records about it have 

survived from ancient times. The first is in Section 53 

of the famous Code of Hammurabi (Figure 1) reported in Webster's New International Dictionary 

(2nd edition) to have been written between 1955 and 

1913 B.C. It contains the following regulation: 

If anyone be too lazy to keep his dam in proper condition, 

and does not keep it so: If then, the dam breaks and all the 

fields are flooded, then shall he in whose dam the break 

occurred be sold for money and the money shall replace the 

corn which he has caused to be ruined.3 

The second of those records was found among 

the ruins of a temple which the Pharoah Akhenaten 

(the older brother of Tutankhamun) built in about 

1400 B.C. at Tell 'Armarna, Egypt, in honor of the 

god Ra who he had intended would replace Egypt's 

Pantheon. It consisted of the following inscription 

proclaiming that his new faith would endure 

Until the swan grows black 

And the Raven becomes white: 

Until the Mountains rise up and walk, 

And the waters flow uphill fitalics added].4 

Ditches were the earliest structures devised for the 

control of water on the great flood plains of rivers like 

the Nile, Hwang-Ho (Yellow), Tigris-Eurphrates, 

and Indus. They served two purposes: first, to drain 

off the excess water after floods, and second, to irFIGURE 1.—Portion of the Code of Hammurabi. 

(Courtesy of the Louvre, Paris.) 

rigate the crops during the long dry periods. There 

were, however, other locations, namely the oases in 

deserts, where such ditches served only the latter purpose, i.e., irrigation. 
NUMBER 28 

It is of interest to note in this connection that many 

desert communities developed essentially the same type 

of water clock for the sole purpose of limiting the 

amount of water that each of the farmers in those 

communities were allowed to take from the irrigation 

ditches.5 The method still in use at the Oasis Ghadames in Western Libya, provides an excellent example 

of one of those clocks and of the procedures that were 

followed there for the past thirty or more centuries: 

At the spring "Ain El Fras" at the Oasis Ghadames, the 

amount of time the landowners are permitted to draw water 

for their gardens from the irrigation ditch, has been controlled during the past 3000 years or more by the methods 

shown here [Figure 21. At the local marketplace (quite some 

distance from the ditch) is a shallow well presided over by 

an attendant who lowers a bucket into the well until it becomes filled with water. Then he raises it, hangs it onto a 

nearby peg while he makes a record thereof by tying a knot 

into a fiber from the bark of a palm tree. The water drains 

back into the well through a hole in the bottom of the 

FIGURE 2.—Oasis Ghadames: a, c, the "water clock" at the market 

place; b, the reservoir at the spring, Ain el Fras; d, gardeners diverting the irrigation water. (From Schaack, "Vergangenheit.") 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

bucket, and when empty, the procedure is repeated (over and 

over again day and night, each cycle requiring about five 

minutes). Each landowner in turn is allowed to divert into 

his garden, water from the irrigation ditch for the time it 

takes for the bucket to be filled and emptied a certain number of cycles depending upon the pioportion of land he owns 

in the area. He must be ready to open his water gate at the 

beginning of the particular series of cycles that are allotted 

to him, and upon the completion of that series, he must close 

his gate and allow the water to pass on to the next landowner in line, who will be waiting his turn. Although modern clocks would accomplish the same results with fewer 

complications, there does not seem to be any inclination to 

change this ancient practice.6 

One observation regarding this desert practice merits particular mention here. It is that from time immemorial, these people were acquainted with one of 

the basic concepts in hydraulics, namely that the 

amount of discharge taking place in any irrigation 

ditch (or in any stream of water) is a function of 

time. 

Much more technologically advanced structures devised for the control of water are the famous Roman 

aqueducts. Although Sennacherib's aqueduct at Jerwan in northern Iraq

 7 is perhaps 400 years older 

than the first of the Roman aqueducts and ranks 

among the earliest of such structures, the Roman 

aqueducts (begun in about 300 B.C.) are of the greater interest here because of the water-measuring facility, the quinaria, which is associated with them. 

The quinaria is a unit of measurement, by which 

water is apportioned. Apparently first introduced by 

the Romans, it was defined by a circular area about 

VA "digits" in diameter. Sextus Julius Frontinus, the 

Water Commissioner of Rome in about A.D. 97 mentioned its origins in his writings: 

According to those who ascribe it to Vitruvius and the 

plumbers, it [the quinaria] took its name from the circumstance that a flat sheet of lead, five digits wide, made up 

into a round pipe, will form this adjutage.9 

By "adjutage," Frontinus had reference to the pipes 

that were inserted through the walls of Rome's supply reservoirs through which water was delivered to 

the conduits of the various consumers. Numerous 

sizes eventually became available, with each adjutage 

stamped with the number of quinariae present in their 

respective cross-sections. The consumer, at regular 

intervals, paid to the State a sum computed by multiplying the unit price of a quinaria by the number 

stamped on his adjutage. 

No serious attention was paid to the elevations at 

which these adjutages were located in the walls of 

the reservoirs, nor to any other inequities which could 

be found with the system. Nevertheless, this is one 

of the earliest known methods of measuring directly 

the flow of water. This same erroneous technique was 

also applied to measuring the flow in open channels. 

The water master merely measured the wetted crosssectional area of the channel to determine the number 

of quinariae. He was not concerned as to whether the 

location of that measurement was at a narrow and 

shallow, or wide and deep place in the channel. Frontinus himself made a number of such measurements 

to determine whether the number of quinariae flowing into the reservoirs corresponded with the number 

of quinariae delivered to the consumers. When he 

found that there was an enormous discrepancy, he 

began to question the honesty of his deputies rather 

than to question the validity of his stream-gaging 

methods.9 

The circumstances just described characterize the 

state of the art of stream gaging from ancient times 

forward. Mistakenly based on the concept that the 

discharge of water is equal to the wetted cross-section 

of an open or closed channel (Q = A), the concept of 

the discharge of streams as a function of time was not 

considered. There was at that time, however, one 

person who took exception to the current theory— 

Flero of Alexandria. 

Hero of Alexandria was a Greek mathematician 

and mechanician of the first century A.D. His accomplishments, too numerous to list here, are so impressive that one school of thought has contended that he, 

like Nostradamus, was a mythical character who had 

been credited with having conceived almost every extraordinary mechanical device then existing. In any 

event, in his book, Dioptra, he described a way to 

measure the discharge of a spring, which is now 

known as the volumetric method (Figure 3). This 

method which has never been surpassed in accuracy, 

is based on the concept that the area of a channel 

multiplied by the velocity of flow equals the amount 

of water passing a given point at a particular moment 

in time. 

Given a spring: To determine its flow, that is, the quantity 

of water which it delivers ... . 

Now, it is necessary to block in all the water of the spring 

so that none of it runs off at any point, and to construct out 

of lead, a trough having a rectangular shape. Care should be 

taken to make its dimensions considerably greater than those 

of the stream of water. It should then be installed at a 
NUMBER 28 

FIGURE 3—The world's first valid streamflow measurement as described by Hero of Alexandria, 

first century A.D. (Drawn by A. H. Frazier.) 

place such that the water from the spring will all flow 

through it That water will cover a portion of the 

cross-section of the trough at its mouth. Let this portion be 

for example, 2 digits in height. Now suppose that the width 

of the trough is 6 digits; 6 X 2 = 12. Thus the flow of 

the spring is 12 1 square] digits. 

It is to be noted that in order to determine how much 

water the spring supplies, it is not sufficient to merely find 

the area of the cross-section of the flow, which in this case 

we say is 12 [square I digits. It is also necessary to find the 

speed of the flow. The swifter the flow, the more water is 

supplied by the spring, and the slower it is, the less. One 

should therefore dig a reservoir to receive the flow, and note 

with the help of a sun dial how much water flows into that 

reservoir in a given time, and thus calculate how much will 

flow in a day. It is therefore unnecesary to measure the area 

of the cross-section of the stream, for the amount of water 

will become clear from the measurement of the time.

 I0 

I Italics added.] 

Although his technique is primitive, in the foregoing description will be found all of the elements that 

enter into the most fundamental modern equation 

pertaining to streamflow namely Q = AV (i.e., the 

quantity of discharge is equal to the wetted crosssectional area multiplied by the average velocity of the 

stream). This equation applies equally well to the 

movement of avalanches, mud-slides, and any number 

of similar phenomena. Unfortunately, Hero's concept 

and methodology were apparently too far ahead of 

his time. Little attention was paid to them until after 

the Dark Ages. When those who ultimately adopted 

Hero's volumetric method and applied it to the design of equipment in modern hydraulic laboratories, 

they probably did so without realizing that Hero had 

conceived the idea as much as 1900 years earlier. 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

EMERGENCE OF MODERN HYDROMETRIC METHODS 

Q = A vs Q = AV 

As previously mentioned, the prevailing method of 

measuring streamflow in ancient Rome persisted well 

into modern times. As noted, it consisted merely of 

measuring the wetted cross-section of a stream and 

accepting the area thus obtained for the figure that 

represented the discharge. The calculation was based 

simply on the equation, Q = A (quantity equals the 

cross-sectional area). On Christmas day, 1598, when 

a great flood occurred on the Tiber River at Rome, 

one Giovan Fontana was still using that equation and 

technique when he undertook the task of determining 

the maximum discharge that occurred during that 

flood. 

Fontana waited for the streams that had contributed to the flood to return to their normal flows. Starting with the Tiber River near Perugia, some 80 miles 

north of Rome, and also for all of the streams entering the Tiber between that point and Rome, he 

measured their wetted cross-sections. At the same 

time, he determined from the highwater marks that 

remained alongside of those sections the probable 

areas that the water had occupied when the river and 

its tributaries had been in flood. 

The water in the Tiber, at the Castello di Corbara, nearly 

a mile above the confluence with the Paglia River, is ordinarily 299 palms wide, and has an average depth of 14'/2 

palms. At the time of the flood, its width was 377Vi palms, 

and it had risen 36 palms. The increase amounted to 135 

[square] canna and 90 [square] palms." 

After computing the amounts which each tributary 

(including the upper end of the main river) had increased on that occasion, Fontana added them all 

together, and concluded that "the measurements of 

the Christmas flood show that the area above Rome 

contributed into the Tiber (at Rome) 500 [square] 

canna and 9 [square] palms more than the river ordinarily carries."

 12 

It will be recognized that the method Fontana had 

used for gaging these streams was identical to that 

which Frontinus had used back in A.D. 97 when 

measuring the streams which contributed water to the 

Roman aqueducts. To modern hydraulic engineers, 

who are accustomed to expressing river discharge in 

terms of cubic feet per second, neither Frontinus' nor 

Fontana's results would have any quantitative meaning. In fact, they even failed to convey any meaning 

to one of Fontana's illustrious contemporaries, Benedetto Castelli (1577?-1644) (Figure 4). In a book 

entitled Delia Misura DelVAcque Correnti [The Mensuration of Running Waters], first published in 1628 

and translated into English in 1661 by Salusbury,13 

Castelli completely refuted the validity of the Q = A 

equation. 

A large portion of Castelli's book was devoted to 

explaining the nature of velocity and how it affects 

the flow in rivers, a phenomenon that both Frontinus 

and Fontana had not considered. Castelli's work received high acclaim and recognition. Galileo, for 

example, referred to it as a "golden book," and even 

today there are many who refer to Castelli as the 

"Father of Modern Hydrodynamics."

 14 

FIGURE 4.—Benedetto Castelli. 

(Courtesy of Hunter Rouse.) 
NUMBER 28 

The date and place of Castelli's birth is somewhat 

in doubt. Gillispie gives it as 1578, although Poggendorff and several earlier authorities noted it as 1577.15 

Although most authorities claim that he was born in 

Brescia in northern Italy at the foothills of the Alps, 

the earliest biographical sketch of him, published in 

1661 by Thomas Salusbury, states that he had been 

born "near Lake Thrasimenus (Trasimeno), where 

Hannibal overthrew the Roman Legions."

 1G

 Lake 

Trasimeno is near Perugia, close to the upper end of 

the reach of the Tiber River where Fontana had 

measured that devastating flood of 1598. 

Be that as it may. Castelli's parents entered him 

into the Order of Black Friars while he was quite 

young, and he became one of the monks (and later 

an abbot) in the Benedictine Order at Monte Casino. 

The Monte Casino Monastery was located on a high 

promontory about 87 miles south of Rome. It was 

destroyed by bombs during World War II, but was 

subsequently rebuilt at a somewhat lower level. Within this monastery the previously mentioned report on 

the Roman aqueducts by Frontinus had been copied 

and preserved. Castelli had doubtless read it there 

because in his book, he strongly repudiated the Q = A 

concept of making streamflow measurements as described therein. 

While at Monte Casino, Castelli had become an 

outstanding student of mathematics, a talent that 

brought him to the attention of the great Galileo. It 

is known that as early as 1603 Castelli had watched 

Galileo demonstrate the principle of his "thermiscope" 

during a lecture at the University of Padua, but apparently it was not until about 1611 that the two had 

become closely associated. Castelli moved to Florence 

in April 1611 to be with Galileo, where he became 

one of the greatest of Galileo's pupils.17 When Galileo 

made his famous discovery regarding sun spots, it was 

Castelli who devised telescopic techniques for plotting 

their movements, which proved Galileo's observations 

thereon to be correct. Furthermore, when Galileo ran 

into trouble with the powerful ecclesiastical forces (as 

he did on several occasions), Castelli was always the 

first to advise and defend him. On the other hand, 

Galileo consistently and lavishly praised the accomplishments of his protege. At his recommendation, 

Castelli became professor of mathematics at Pisa, a 

chair that he occupied from 1613 to 1616.18 

While teaching at Pisa, Castelli became interested 

in the motion of water in rivers. Pisa is located on 

the Arno, an extremely unruly river that is subject 

to frequent and devastating floods. Attempts to control the river can be traced as far back as the year 

A.D. 1077. The best engineering talent in Italy had 

been brought to bear in that effort. About 100 years 

prior to Castelli's arrival at Pisa, Leonardo da Vinci, 

the greatest engineer of the Renaissance had worked 

on that project. Of his work thereon, General William 

Barclay Parsons has expressed the following views: 

In the development of his new design, Leonardo gave the 

most advanced exhibition of creative engineering imagination that so far had been conceived, and it is doubtful, when 

his complete lack of precedent and of accurate knowledge 

are compared with the wealth of both that has been accumulated since, whether his work on the Arno has ever 

been surpassed as a feat of advance.19 

Under those circumstances, and in the light of what 

follows, it would seem quite unusual if Castelli had 

not learned as much as he could about Leonardo and 

his work on this river. Abraham Wolf states that Castelli was "deeply influenced by the Leonardo school, 

and [was] probably familiar with the Vatican compilation of Leonardo's notes."

 20 

Early in 1626 he sent to Galileo at Florence for his 

consideration, two treatises on that subject. During 

that year also, he was called to Rome by Pope Urban 

vin to serve as the papal consultant on hydraulics and 

as professor of mathematics at the University of 

Rome.21 Within two years thereafter, his famous book 

Delia Misura DelTAcque Correnti (perhaps die final 

version of the two treatises he had sent to Galileo) 

was published. 

The early chapters of Castelli's book were devoted, 

as previously mentioned, to a condemnation of die 

method of measuring streamflow as had been practiced by Frontinus during the early years of the Roman Republic, and later by Fontana in his measurement of the 1598 flood on the Tiber River. Most of 

the remaining chapters contained his explanation of 

the nature of velocity and its relation to the discharge 

of rivers. A few (slightly modernized) extracts of Salusbury's translation of Castelli's work are presented 

below.22 When reading them it should be kept in mind 

that in general, these were the first statements to have 

been published dealing with such subjects. Although 

some of the terminology is archaic, the basic concepts 

are still sound. 

DEFINITION OF STREAMFLOW MEASUREMENT.—To measure a river or running water is, in our sense, to find out 

how many determinate measures, or weights of water in a 

given time passeth through the river or channel of water 

that is to be measured." 
8 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FLOATS FOR DETERMINING VELOCITY.— [The velocity of 

the water may be determined by] keeping account of what 

space a piece of wood or other body that swimmeth, is carried by the stream in one determinate time, as for instance, 

50 pulses .. .

 2* 

PENDULUM FOR TIMING OBSERVATIONS.—Because it will 

often be requisite to measure time exactly in the following 

problems, we take that to be an excellent way to measure 

time, which was shewed me many years since by Signore 

Galileo Galilei, which is as followeth: A string is to be taken 

three Roman feet long, to the end of which a bullet of lead 

is to be hanged of about two or three ounces; and holding 

it by the other end, the plummet is to be moved from its 

perpendicularity a palm more or less, and then let go, which 

will make many swings to and again, passing and repassing 

the perpendicular before it stay in the same. Now it being 

required to measure the time that is spent in any whatsoever operation, those vibrations are to be numbered that are 

made while the work lasteth; and they shall be so many 

second minutes of an hour if the string be three Roman feet 

long. But in shorter strings, the vibrations are more frequent, 

and in longer, less frequent; and all this followeth whether 

the plummet be a little or much removed from its perpendicularity, or whether the weight of the lead be greater or 

lesser.25 

CONTINUITY OF FLOW IN STREAMS.—•. . . those streams 

which carry equal quantities of water in equal times make 

not the same depths or measures (widths) in the river in 

which they flow unless when flowing in the river they acquire 

—or to say better—keep the same velocity. . . . 

Because of Castelli's strong disapproval of Fontana's methods, it seems rather peculiar that in 1640, 

he arranged to have Fontana's report of that 1598 

flood republished. The fact that he had done so is 

shown in Figure 5 which represents the cover page 

thereof, and the cover page of one of the more recent editions of Castelli's Delia Misura Dell'Acqua 

Correnti. The dates at which both of these reports 

originally appeared—1599 and 1628 respectively— 

mark the time at which the old Q = A concept was 

contested, and the time at which the modern Q = AV 

concept began taking its place. 

Free Floats 

With a change of focus from other-worldly concerns 

to those of the nature of the real world, the Renaissance in Europe stimulated the efforts of many remarkable men, most notable among them being Leonardo da Vinci (1452-1519). 

Among the more than 8000 note sheets still extant 

on which Leonardo da Vinci had written and drawn 

sketches, by far the greatest number of entries on any 

major subject therein was concerned with hydraulics. 

The one group of entries, which is of greatest concern 

at present, is that which dealt with the velocity distribution of the water in rivers. Philosophers of the Middle Ages had contended mistakenly that the water in 

rivers flowed much faster near the bottom than at the 

top. In support of that contention, they would point 

to the well-known circumstance that if several holes 

were drilled in a large wooden tank filled with water, 

the velocity with which the water emerged from the 

lower hole was always greater than that from any of 

the other holes. To them, the conditions which prevailed in large water tanks were identical to those in 

large rivers, and they would condone no experimentation that would either confirm or deny any of 

their conclusions. 

Leonardo, who was intensely curious about all aspects of nature, was also a firm believer in experimentation as the premise upon which to base belief. 

According to one eminent authority, Dr. Carlo Zammattio, that intense curiosity "set him completely 

apart from those who preceeded him. His advent 

brought to the world a new age which aspired above 

all to UNDERSTAND." His notebooks reveal the manner 

in which his experiments were made on the velocitydistribution in rivers. The sketch and notes about the 

rod floats he had made for that purpose appear in Figure 6 along with a recently-built replica of one of 

them.72 Figure 7 contains the author's concept, based 

on a group of such notes, showing Leonardo behind 

his odometer keeping abreast the float near the middle 

of the river. The project involved the following operations : 

1. His helper would release a float of just the 

proper length (short enough so as not to drag against 

the bottom) several yards upstream from the line 

stretched across the river. 

2. Leonardo would wait at that line with his odometer set at "0. " When the float arrived, he would start 

pushing the odometer down the path, keeping abreast 

the float, and singing the musical scale up and down 

say ten times. (According to Marinoni, he had trained 

himself to sing the scales at a precise rate, and knew 

the number of seconds it would take him to sing any 

number of them. He preferred that method to counting his pulse because it was more convenient and under most circumstances, more accurate.)

 28 

3. Upon completing that "song," Leonardo would 

stop abruptly, note the distance recorded on the odometer and, from the number of times he had repeated 

those musical scales, the time required for the float 
NUMBER 28 

MESVRE RACCOLTE 

DA GIOVAN 

FONTAN A 

ARCHITETTO, 

DeWosiccrcfcitnento chehatmof&t. 

to it Fiumi, Torrenti, e fop che 

hanno caufato C inondatwnc a 

T^oma d "NataU, 1598 . 

Riftampataadinftanza delSig. 

Domenico CafteJIi. 

IN ROMA 

Apprcflb An tonio Marian , Gioiofi • 

M. DC . XXXX. 

DELLA MISVRA 

DELL ACQVE 

C O R. R E N T I 

D l D. BENEDETT O CASTELL I 

It 

Ab\>at c di S. 3medettoMoyfw,e Matcnuttico 

DI PAPA VRBANO VIIIProfefsore ncllo Studio di Roma. 

In auejla term edizjone accrefctuta del Second* libro, t di 

moke curiofe Scritture mm ptu flamfAte. 

ALL' ILL" ° E REV.MO SIGNO R 

ABBATE VRBANO 

SACCHETT L 

la BOLOGNA, per gtiHH. itl Dam . M. DC.LJt. 

FIGURE 5. Title pages of Fontana's and Castelli's books. These books symbolize the passage 

of the old Q = A concept and the advent of the modern Q = AV concept for measuring water 

flow in conduits and in open channels. 

to have traveled that far. From this he would compute the float's velocity. While all this was taking 

place, he would have observed whether the float tilted 

forward or backward, thereby noting whether the 

velocity near the top of the stream was greater or less 

than near the bottom. 

4. He would finally retrieve the float and return 

again to the point of beginning. His assistant would 

thereupon release another float at a greater distance 

from his side of the river. The whole procedure would 

then be repeated until the entire width of the stream 

had been covered and the velocity distribution 

throughout its entire cross-section had been determined. 

The conclusion Leonardo arrived at after having 

completed his experiments is noted in several places 

in his notebooks, but perhaps most completely in 

Codice Atlantico, folio 124 r. a, which has been translated as follows by MacCurdy: 

Of water of uniform weight, depth, breadth and declivity, 

that portion is swifter which is nearest the surface; and this 

occurs because the water that is uppermost is contiguous to 

the air, which offers but little resistance through its being 

lighter than the water; and the water that is below is contiguous to the earth, which offers great resistance through 

being immovable and heavier than water. It follows that the 

part which is more distant from this base has less resistance 

than that above which is contiguous to the air, for this is 

light and mobile.28 

Leonardo's rod float is the earliest device to have 

been found so far that was specifically designed for 

the purpose of measuring stream velocities. The additional feature it provided, namely that of indicating 
a 

»1V«M| 

BLADDER 

"Let the rod project one braccio at 

A N so that the displacement of the 

brick can be distinguished at A N." 

ROD 

"This demonstrates whether the water 

is flowing faster below or at the 

surface." 

fc^b**' 

FIGURE 6.—Leonardo da Vinci's rod float for investigating the subsurface water velocities in 

streams, as reconstructed by the author (a), from Leonardo's notes, (b) .(From da Vinci, Manuscript "A," folio 42 v.) 
NUMBER 28 11 

FIGURE 7.—Leonardo conducting experiments on the velocity-distribution in streams. 

(Drawn by A. H. Frazier.) 

whether the surface or bottom velocities were greater, 

reflects some of the special genius with which Leonardo was endowed. 

It may be interesting to note here that when 

Leonardo conducted these experiments, he obtained 

enough data (a detailed cross-section of the stream 

and velocity observations at numerous locations therein) to compute the stream's actual discharge. No 

evidence has been found, however, that he had pursued any such objective, although on more than one 

occasion he had studied the rate of flow through orifices. Apparently his only plan on this occasion was to 

make a velocity-distribution study. Aside from wanting to satisfy himself as to what the true circumstances 

were, he might also have wanted to demonstrate that 

the theories of contemporary philosophers (for whom 

he had very little admiration) were wrong. 

Although Leonardo's paintings and writings about 

art had received wide acclaim both during and after 

his lifetime, his 8000 or more pages of scientific notes 

failed to attract any immediate or widespread attention. At several places in those notes, he had expressed 

an intention to reorganize for publication those particularly relating to hydraulics. He had prepared several 

lists of chapter headings, and in several other instances 

he had drafted one or more paragraphs which were obviously intended for use in such a publication. He 

never made, however, any further progress thereon 

before his death. Moreover, the persons who subsequently got possession of those notes only seemed 

interested in those which related to painting. 

Finally, an eminent hydraulic experimenter named 

Giovanni Battista Venturi (see pages 37-40) published, in 1797, a booklet entitled Essai sur les ouvrages 

physico-mathcmatiques de Leonard de Vinci, which, 

at long last, focused attention on Leonardo's remarkable scientific achievements. Suddenly the dozen or 

so persons and libraries that had acquired any pages 

from Leonardo's notebooks found themselves in possesion of unexpected and priceless treasures. 
12 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

^JJLL-^.,.^^., . 35RS97?m 

a 6 c 

FIGURE 8.—Earliest floats post-dating Castelli's book on water velocities: a, Cabeo's rods, ca. 

1646; b, Barattieri's rod float, ca. 1663; c, Mariotte's double float, ca. 1680. (Drawn by A. H. 

Frazier, from Masetti, "Descrizione.") 

FIGURE 9.—Brunacci's combination single and double float, 

ca. 1805. (Drawn by A. H. Frazier, after Masetti, "Descrizione.") 

I 

Side vitw of Surface Float 

uTop view of Surface Float 

iLi-—L . 

IL 

TprW' Section of Sub-Surface Float 

Top view of Sub-Surface Float 

FIGURE 10.—A double float, such as was designed and used 

by General Ellis on the Connecticut River, ca. 1875. 
NUMBE

R 28 

13 

There can be little doubt that men had long been 

aware of the existence of velocities in rivers by merely 

having observed materials floating on them. Accord-

ingly, floats became the first and most natural facility 

for studying velocities. It has already been shown that 

Leonardo used floats for that purpose, although his 

unpublished observations thereon failed to either come 

to the attention of, or to motivate, any immediate 

followers. In fact, more than 100 years elapsed before 

Benedetto Castelli's work aroused any general interest 

in the subject. Many scholars, including Abraham 

Wolf, have noted many similarities between Cas-

telli's comments about water velocities and those of 

Leonardo da Vinci's, and have expressed their beliefs 

that Castelli had made use of many of Leonardo's 

observations thereon when writing his book. Never-

theless, Leonardo had attracted relatively few (if any) 

immediate followers in this field, whereas Castelli had 

attracted a large number of them. It was Castelli's 

proposal to use floats for measuring velocities, not 

Leonardo's, that started the vogue in that respect, 

a vogue which has never completely disappeared. 

Among Castelli's numerous followers were several 

who preferred to use rod floats which, like Leonardo's, 

would travel in an upright position; others preferred 

wooden spheres, or balls of wax. It would be almost 

an endless task to describe them all, but a fair idea of 

how some of them appeared can be obtained from 

Figure 8 which shows three models used before the 

end of the 17th century by Nicola Cabeo (1585-

1650), G. B. Barattieri (1601-1677), and Edmc Mari-

otte (1620-1684), respectively. An additional feature 

(Figure 9) introduced by Vincenzo Brunacci (1768-

1818) in about 1805, consisted of merely providing a 

separate and completely loose ball along with Mariot-

te's double float. This additional ball was allowed to 

travel with the double float during each of its "runs." 

Its speed was generally greater than that of the double 

float because it was not held back by the more sluggish 

lower ball. Here, according to Masetti, is what Brun-

acci achieved with such equipment: 

Having determined with an ordinary float the speed at the 

surface, and having simultaneously measured the velocity at 

which the two-ball assembly travelled, he could quickly find 

FIGURE 11.—One of James Francis' rod floats. From the 

large set of rod floats used by James Francis while Chief En-

gineer of the Proprietors of Locks and Canals, Lowell, Mass-

achusetts, ca. 1855. It is held by one of his successors, George 

Whitaker (1907-1962). 
14 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

the speed of the current at the depth to which the heavier 

ball had been lowered by using a very simple formula based 

on the theory of such a meter.30 

It should not be assumed from the foregoing remarks that free floats became increasingly scarce 

during the later centuries. Like practically all early 

velocity-measuring devices, they continued to make 

sporadic appearances even up to the present. With 

the publication of Humphreys' and Abbot's famous 

report on the Mississippi River, for example, double 

floats similar to that designed by Mariotte received 

official endorsement: 

Various methods were resorted to. Saxton's current 

meter was tried, but proved to be unsuited to measurements 

in a river of such great depth and violence of current. Only 

double floats were found to give reliable results. [Italics 

added.]

 31 

Perhaps the most carefully designed double floats 

(Figure 10) ever to have received actual field use 

were those that General Theodore G. Ellis (1829-

1883) made for his studies on the Connecticut River 

between 1867 and 1877 under General Humphreys. 

Perhaps the best rod floats (Figure 11) ever to have 

been designed, were those of the set used by the distinguished hydraulic engineer, James Francis (1815-

1892) of Lowell, Massachusetts, who (among other 

purposes) used them to develop the famous Francis 

Weir formulas. 

FIGURE 12.—Camillo Agrippa, his ship, and ship's log, ca. 1595. 

(From Agrippa, Nuove Inventione.) 
NUMBER 28 15 

Tethered Floats 

The advent of "free" floats was followed by one 

that will be called here "tethered" floats, because 

the major feature thereof consisted of a ball, generally 

heavier than water, to which a cord was attached to 

limit the distance that it could travel downstream. 

The use of such devices had been anticipated in the 

navigation field by an early ship's log, a description of 

which appeared in a booklet entitled Nuove Inventione di Camillo Agrippa, published in 1595.32

 A portrait of Agrippa, his ship, and a close-up view of his 

invention appear in Figure 12. As may be seen in the 

close-up view, the device consisted of a large frame 

shaped like a carpenter's square which would be suspended either from the ship's foremast, or from a 

boom extending outward from the ship's rail. Its 

downstream leg, which was graduated throughout its 

length, would be brought to rest horizontally, just 

above the water's surface. The ball, heavier than 

water, was suspended from a cord fastened to the 

upper edge of the frame, the cord being sufficiently 

long to permit the ball to be submerged a foot or two 

below the surface of the water. As the ship moved 

forward, the ball would lag behind the other parts of 

the frame by an amount that depended upon the 

speed of the ship. The extent of that lag could be 

observed from the position of the cord as it crossed 

in front of the scale on the horizontal leg. By positioning those graduations appropriately, the actual speed 

of the ship could he read thereon. 

Whether Domenico Guglielmini (1655-1710) had 

ever heard of Agrippa's ship's log is not known, but 

in his book, Aquarium Fluentium Nova Methodo Inquisitia, published in 1690 and 1691, he described a 

velocity-measuring facility called a "quadrant and 

ball," which operated on exactly the same principle. 

Figure 13 shows two positions of the ball (as would 

be caused by two different velocities), and force diagrams that he used for determining the proportions 

the two velocities bore to each other. 

Guglielmini (Figure 14) became the most highly 

FIGURE 13.—Guglielmlni's "quadrant and ball," Ca. 1690. 

The force diagrams indicate the proportions one velocity 

bears to another. (From Guglielmini, Opera Omnia.) 

FIGURE 14.—Domenico Guglielmini. 

(Courtesy of Hunter Rouse.) 
16 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

respected hydraulic engineer in Italy during his time. 

He was born in Bologna 27 September 1655 and received an exceptionally good education. A degree of 

Doctor of Physics was conferred on him by the University of Bologna in 1678. His greatest interests first 

centered around astronomy, but they soon shifted to 

hydraulics. The Senate of Bologna then appointed 

him to the positions of First Professor of Mathematics 

and General Superintendent of Waters. While holding 

those positions, he wrote several treatises about flowing water, the first of which has been cited above. In 

1694 the City of Bologna founded a new chair of 

Professor of Hydrometry in its university and gave it 

to him. The word "hydrometry" made its first appearance in that title. After having published a book on 

The Nature of Rivers in 1697, he was chosen a member of the Italian Royal Academy of Sciences. One 

of his early biographers reported, "This book—an 

Original of its kind, made a great Noise . . The 

Common-wealth of Venice, envying the Happiness of 

Bologna, called him in the Year 1698 to the Professorship of the Mathematicks at Padoua.'' 33

 In 1702 he 

became that university's Professor of Theoretical 

Physics. Soon thereafter, chemistry became his favorite subject, so before long he wrote a few books on 

chemistry. The last thereof was published during the 

final year of his life, 1710. 

Because of the great advances in hydraulics since 

the 17th Century, most modern hydrographers are not 

likely to display as much enthusiasm for Guglielmini's 

work as did his contemporaries. While most of it was 

quite sound, his quadrant and ball produced very 

misleading results particularly when used on deep 

swift rivers. Its fault rested in the fact that it failed 

to eliminate the effect of the pressure which the flowing water exerted against the cord from which the 

lower ball was suspended. As that ball came closer to 

the bottom of the stream (where lower velocities normally occur, and where the angle as read on the quadrant should become smaller), the drag of the water 

against the greater length of cord which was paid out 

would more than offset the decrease of pressure 

against the ball, and the angle read on the quadrant 

would become larger. Obviously unaware of that inherent fault in his instrument, Guglielmini stated unequivocally at several places in his earlier works that 

the velocity at the bottom was greater than near the 

top. He is said to have changed that belief in later 

years, but so far, no evidence has ben found to indicate that he attributed any of that error to his instrument. Just how much that effect could distort 

the true results will become evident by comparing the 

Feet per Second 

0 5 10 15 20 2. 

Feet per Second 

20 

40 

60 

80 

at 

x> 

100 Bottom 100 

0 

20 

40 

60 

80 

00 

Max. 

FIGURE 15.—Comparison of Guglielmini's erroneous vertical velocity curve with its modern 

counterpart: a, Guglielmini's curve developed with his quadrant and ball; b, modern curve 

developed with modern equipment. 
NUMBER 28 17 

vertical velocity curves shown in Figure 15. At the 

right thereof is what modern hydrographers have 

found to be the correct general shape of such curves, 

whereas to the left of it is the same type of curve 

based on data which Guglielmini himself observed 

with his quadrant and ball on a 35-foot-deep river.34 

It will be seen that one is practically the reverse of the 

other insofar as the vertical velocity distribution is 

concerned. 

Despite its faults, Guglielmini's quadrant and ball 

attracted many followers. Figures I6a-d show two of 

the various types which were obviously inspired by his 

model. Figures 16a, b resemble his original model 

closely; those in 16c, d reflect a preference for a 

weighted rod rather than for a weighted ball; Figures 

16tf, / differ from the others in that the quadrant has 

been replaced by spring scales; and those in I6g, h 

illustrate an innovation which, although much more 

cumbersome for use in deep swift water, would tend 

to eliminate much of the fault found with Guglielmini's original model. 

^*«^3i^3^^^^5»i^5J^^iiiti^gSiw^*^ 

^3*guri!a^ia^ti!^>*=awi=^i!SisSj^»i!=5Si' 

FIGURE 16.—Successors to Guglielmini's quadrant and ball: 

a, Cava's square, ca. 1721; b, Ximenes' quadrant, ca. 1752; 

c, Ferrari's sectional rod, ca. 1796; d, Venturoli's compound pendulum, ca. 1796; e Ximenes' clock-spring device, 

ca. 1752; /, Ximenes' spring-scale device, ca. 1752; g, Lorgna's device, ca. 1777; h, Barbantini's hydraulic counterweight, ca. 1814. (Redrawn by A. H Frazier after Masetti, 

"Descrizione") 
18 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

PADDLES 

Man's early use of crude paddles to help propel a 

log or raft across a stream obviously extends back into 

prehistoric times, and the principles learned on those 

occasions ultimately became applied to a considerable 

group of current meters. The forces that are in 

effect when paddles are placed in water do not always 

produce the same results. If a person sitting in a canoe 

applies a backward force to the paddle, for example, 

the canoe will move forward, whereas if the person 

were sitting on the bank of the stream and held the 

paddle in the current, the paddle would tend to be 

pushed backward. It is this latter effect that was 

ultimately adopted in the design of current meters for 

measuring the velocity of running water. 

The amount of force required to hold the paddle 

squarely against the current would depend upon the 

a 

en 

jy# 

o 

FIGURE 17.—Santorio's inventions: a, water current meter; 

b, anemometer. (From Santorio, Commentaria.) 

FIGURE 18.—Gauthey's current meters, ca. 1779. (a, from 

Van Winkel, "Streamflow"; b, drawn and reconstructed by 

A. H. Frazier after Masetti, "Descrizione.") 

dimensions of the paddle and the velocity of the current. By using the same paddle throughout a series of 

experiments, and by using some method of measuring 

the force required to prevent the paddle from swinging 

downstream, the relative speed of the current at many 

different locations could be determined. The actual 

speeds of the water could also be determined thereby, 

but the mathematics involved would be considerably 

more complicated. 

The earliest record of a paddle-type current meter 

was that reported by Dr. Santorio Santorio (1561-

1636). Encyclopedias report that he was the world's 

first iatrophysicist (one who explains diseases of the 

body in terms of physics rather than of chemistry), 

and the inventor of many useful medical instruments. 

The particular instrument that brought Santorio the 

most acclaim was his invention of the clinical thermometer. It was similar to Galileo's thermometer 

(which was designed to measure atmospheric temperatures), but Santorio modified it in such a way to 

measure body temperatures of his patients who were 

afflicted with a fever. In 1610, he turned his attention 
NUMBER 28 19 

^e»*»3»»«jsi?^«6feifjg»£H«fe*' 

FIGURE 19.—Ximenes' paddle type current meters, ca. 1780. 

(Drawn by A. H. Frazier after Masetti, "Descrizione.") 

J&SJT/. 

~^se*r±\/('—^" y?*/*r's/f/f//-< • 'J/rffc"""c/stf 

&&TJJ 

FIGURE 20.—Christiaan Bruning 

and his current meter, ca. 1788. 
20 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

to the construction of an anemometer and a water 

current meter (Figure 17). As Carlo Zammattio has 

pointed out, Santorio had made his drawings known 

to the public before 1611, almost 18 years before the 

first edition of Castelli's famous work on water velocity was published. The circumstances under which 

they were invented, as translated by Zammattio from 

Santorio's book Commentaria In Primam Fen Primi 

Libri Canonis Auicennae, are presented below: 

Some people are benefited, and others harmed during 

rainy weather. Similarly, the heavy impact of falling or 

running waters tends to produce sleep in some, and to prevent sleep in others. But I would like to mention here a 

condition I had observed in Croatia, where there is a place 

renowned for the noise of winds, and for the great tumult 

of rushing waters. At some times people of the community 

are aroused from sleep by this uproar, and at others they 

are lulled to sleep by that same noise. I therefore proposed, 

as a means of subtly ascertaining the reason for those circumstances, that one should weigh, with a balance scale, the 

amount of impact produced under both circumstances. When 

urged by friends to show how that could be done, I prepared 

two staters (Roman balances) on both of which a plate is 

mounted at right angles. By means of the first (with the 

plate pointing upwards), the impact of the winds could be 

weighed; by means of the second (with the plate pointing 

downwards), the impact of the water. The one having the 

plate pointing upward for measuring the impetus of the wind 

helped us to predict when such winds tended to increase. 

We could thus forecast weather at sea, and could avoid the 

peril of sinking ships. It further provided the means whereby 

we could be more sure as to whether the impact of the winds 

tended to increase or decrease. Other uses for this device are 

described in the book regarding medical instruments. 

The other instrument (on which the plate hangs downwards) allows us to weigh the amount of impact produced 

by running waters. It might have primary usefulness for improving the efficiency of mills and for other applications. In 

consequence of its use, we shall be able to ascertain what 

amount of impact has beneficial properties, and what 

amounts would have harmful properties for our patients. 

Actually, if certain amounts of impetus or noise are salubrious, and others are unsalubrious, by what better means 

could we measure the effectiveness of our medicines?

 M 

Zammattio has suggested that the location in Croatia (now part of Yugoslavia) to which Dr. Santorio 

had referred, may have been at the great Caverns of 

St. Canziano del Carso, some 60 miles east of Trieste, 

Italy. There a river disappears with a tumultuous roar 

into a vast underground cavern. There also, occurs 

the "bors"—a terrific wind that blows down from the 

European plains throughout the year. 

Although Santorio's device measured only the impact of the water striking the plate (making no 

attempt to convert the results into actual velocity 

FIGURE. 21—Karl F. Keeler (b. 1888) 

and his deflection meter. 
NUMBER 28 21 

values), it should be realized mat the mathematical 

tools for making such conversions had not yet been 

conceived. 

Beginning in 1779 (more than one and one-half 

centuries after the advent of Dr. Santorio's devices), 

a whole rash of paddle-type current meters appeared. 

As a matter of fact, they have continued to do so up 

to the present. The earliest on record of this new crop 

are the two made during 1779 by the great French 

canal builder, Emiland Marie Gauthey (1732-1806). 

Gauthey was a graduate and later an Inspector 

Generale of the Ecole des Ponts et Chausees of Paris, 

the foremost engineering college in the world at that 

time. Gauthey's model (Figure 18a) bears such a 

close resemblance to the one designed by Santorio, 

that it is tempting to assume that he might have heard 

about the doctor's model. It may be noted that while 

the principle of operation is the same in both models, 

that shown in Figure 18a measures the water's impact 

against the plate (while it is kept normal to the current) by means of a balance, whereas the other (Figure 186) measures it by means of a spring scale. 

During the next year Leonardo Ximenes (1716-

1786) introduced the three models shown in Figure 

19. Figure 19a was intended for measuring surface 

velocities only, but Figures 196 and c could be used 

to any depth not exceeding the overall height of the 

framework. 

In all three of Ximenes' models, the panels (or 

blades) were allowed to swing downstream—the degree depending upon the speed of the current—in 

contrast to the earlier equipment in which the blade 

had to be held normal to the current at the time 

readings were taken. In the first model (Figure 19a) 

the pressure against the plate is resisted entirely by 

the weight of the panel itself. In Figure 196 a single 

weight provides the force which resists the pressure 

against the blade (which in this case is suspended to 

swing laterally rather than vertically). In Figure 19c 

the weight of the blade, plus that of an additional 

weight, combine to oppose such pressures. 

Since the manufacture of "paddle-type" current 

meters continues to the present, and therefore, are 

too numerous to cover here, only two additional models will receive attention. That shown in Figure 20 

was designed by Christiaan Bruning (1736-1805), a 

Dutch hydraulic engineer, who had been educated at 

Heidelberg University and who ultimately, in 1803, 

became the Director General of Holland's river and 

sea operations. It may be noted that in his device, die 

impact of the water tended to push the flat plate 

straight backwards, but was restrained from doing so 

through a counter pressure applied at the balance 

scale at the upper end of the support rod. Readings 

obtained from the amount of weight required to establish an equilibrium could be converted into figures 

representing the velocity of the water. Bruning's 

paper

 36

 about this equipment was published in Holland in the late 1780s, for which the Dutch Academy 

of Sciences awarded him a gold medal. 

Reinhard Woltman, whose current meter will be 

discussed later in this study, was a great admirer of 

Bruning, and in 1790, when Woltman published an 

account of his own current meter,37 he included 

therein the drawings of the Bruning meter shown in 

Figure 20. 

The deflection meter shown in Figure 21 was designed by Karl Fairbanks Keeler, an American hydraulic engineer. This meter, constructed in 1937 by 

Leupold, Volpel & Co. of Portland (now Leupold and 

Stevens, Incorporated of Beaverton, Oregon), is perhaps the most sophisticated paddle-type device ever 

built in that it has been interconnected with a waterstage recorder, which registers simultaneously both 

the height of the stream and the angle assumed by 

the blade. Its purpose is to help obtain records of the 

flow in canals that are subject to backwater variations. 

A number of these models have been manufactured 

by the Leupold and Stevens firm. Most of them have 

been installed at gaging stations operated by the International Boundary and Water Commission, United 

States and Mexico, in which Keeler had been employed for many years as the Supervising Hydraulic 

Engineer. 

PADDLE WHEELS 

Paddle wheels similar to those that propelled the 

early Mississippi River steamboats—but much smaller, 

of course—have been used fairly extensively both for 

registering the speed of a ship at sea and the surface 

velocities of the water flowing in rivers. Here again, 

the application in the navigation field was the earlier 
22 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

of the two. The first published record of a paddle 

wheel for use as a ship's log was contained in the first 

volume of Vitruvius' book on Architecture, written 

in about the first century B.C.38 A drawing, based on 

Vitruvius' description of that device is shown in Figure 22. As may be seen, a pair of paddle wheels, one 

on each side of the ship, but mounted on the same 

shaft, drove a train of reduction gears. The final gear 

in the train just cleared a special upper deck in the 

hold of the ship. It had a series of holes through it 

which formed a circle just within its outer circumference. At regular intervals of time a single round 

stone would be placed in each of those holes, and 

these stones would be pushed along by the gear during 

the course of its circular travel. The reduction accomplished by these gears was so great that the ship had 

to travel a distance of one mile to cause each successive hole to reach a point where an opening had been 

cut through that special deck to allow each stone in 

its turn to drop through into a large bronze container 

on the lower deck. Each mile of travel would therefore 

be announced by a loud "clang" as the stone would 

strike against the rim of that container. By counting 

the number of stones that had accumulated therein, 

the Captain could determine the number of miles 

which the ship had traveled. 

This device also could be used to measure velocities 

in rivers by merely anchoring the ship in the current 

and allowing the log to perform its function in the 

same manner as it does when the ship is moving in 

still water. 

European Contributions 

The earliest paddle wheel to have been found so 

far which was built specifically for measuring the velocity of water flowing in open channels, is that made 

by Luigi Ferdinando Marsili (1658-1730), sometimes 

spelled Marsigli (Figure 23). He used it in about 1681 

for studying the velocities in the Bosporus between 

^^z^g^^z^az^^zz^zn^g^z^^^arT^^z^^as^gs^gz 

V/////////////77777, ^////////////////////A 

— ^ Af +fa/t>z 

FIGURE 22.—World's first mechanical ship's log as described by Vitruvius in first century B.C. 

(Drawn by A. H. Frazier.) 
*->>* Cross-Section A-A 

FIGURE 23.—Marsili iMarsigliJ and drawings of his current meter. (Portrait from Enciclopedia Italiana di Scienze; drawings from Milanese, "Santorio.") 
24 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

the Black Sea and the Sea of Marmora, and later on 

rivers in the Danube Valley. A translation of his 

description of that meter, containing a few minor 

modifications from that which was recently prepared 

by Fernando Milanese, an engineer of Milan, Italy, 

follows: 

To measure the velocity of the current at the Leandro 

Tower, I built a wooden apparatus which had a wheel provided with six blades, each about a foot broad. I fastened 

the wheel to a tapered shaft about 5 feet long, and installed 

a pointer at one end to assist in counting the number of 

revolutions performed by the wheel as the water struck 

directly against the lowermost blades. . While holding 

the axle of the wheel in a horizontal position with just the 

lower blades submerged in the water, a six-inch-long pendulum made 100 oscillations while the wheel, as observed 

from the pointer, made 38 revolutions. By performing similar experiments, the velocities of any river can be compared 

to the one that I had measured.39 

Many writers, obviously unaware of Marsili's earlier 

work, have credited Francesco Domenico Michelotti 

(1710-1777), Professor of Mechanics at the University of Torino (Turin) with having been the inventor 

of the paddle-wheel-type current meter (Figure 246). 

His two-volume work on hydraulics entitled Sperimenti Idraulici 40

 contains among its illustrations, the 

two shown in Figure 24. Probably the leading hydraulic engineer in Italy, Michelotti had the opportunity to use most of the velocity-measuring devices 

which were in vogue during his time. Figure 24a appeared at the beginning of one of his chapters. It 

shows most of the equipment that a professional 

hydrographer of the 1760s might have taken on an 

extended field trip. The following items therein can be 

identified: (1) a Pitot tube (invented in 1730); (2) 

a level and leveling rod; (3) a quadrant and ball 

(such as invented by Guglielmini) ; and (4) a wicker 

stool for the comfort of the note-taker of the party! 

One item with which Michelotti also experimented, 

but which does not appear in either of these illustrations, was a paddle-type meter similar to the one previously shown in Figure 18a. 

During the 1700s, leadership in the field of hydraulics slowly shifted from Italy to France. No doubt the 

ample funds that the French government supplied for 

research on this subject did much toward creating the 

change. Then too, during that century, mathematics 

had reached a stage where astute researchers could 

apply it to their hydraulic investigations. 

Prominent among those who made use of both 

laboratory and mathematical facilities was Pierre Louis 

Georges Dubuat (1734-1809), a lieutenant in the 

Royal Corps of Engineers. The eminent engineer, 

writer, and educator, Hunter Rouse has provided the 

following translation from one of Dubuat's works revealing the state of the science as of the 1780s: 

All that concerns the uniform course of the waters of the 

face of the earth is unknown to us; and to obtain an idea 

of how little we do know, it will suffice to glance over what 

we do not: To estimate the velocity of a river of which one 

knows the width, the depth, and the slope; to determine to 

what height it will rise if it receives another river in its bed; 

to predict how much it will fall if one diverts water from it; 

to establish the proper slope of an aqueduct to maintain a 

given velocity, or the proper capacity of the bed to deliver 

to a city at a given slope the quantity of water which will 

satisfy its needs; to lay out the contours of a river in such 

a manner that it will not work to change the bed in which 

one has confined it; to calculate the yield of a pipe of 

which the length, the diameter, and the head are given; to 

determine how much a bridge, a dam, or a gate will raise 

the level of a river; to indicate to what distance backwater 

will be appreciable, and to foretell whether the country will 

be subject to inundation; to calculate the length and the 

dimensions of a canal intended to drain marshes long lost 

to agriculture; to assign the most effective form to the entrances of canals, and to the confluences or mouths of rivers; 

to determine the most advantageous shape to give to boats 

or ships to cut the water with the least effort; to calculate 

in particular the force necessary to move a body which floats 

on the water. All these questions, and infinitely many others 

of the same sort are still unsolvable: Who would believe it? " 

Later, among those same works Dubuat expressed 

the fundamental principle which has thrown wide the 

doors for analyzing mathematically the flow of water 

in conduits and open channels. David Brewster, who 

had himself designed a current meter as will be discussed later, described the circumstances which led to 

that discovery as follows: 

In studying the motion of canals and rivers, it occurred to 

him [Dubuat] that if water possessed perfect fluidity and 

flowed in a channel infinitely smooth, its motion would be 

constantly accelerated like that of heavy bodies descending 

upon an inclined plane. But as the velocity of a river is not 

accelerated ad infinitum, but soon arrives at a state of uniformity, and is not afterwards increased without some cause, 

it follows that there is some obstacle which destroys its accelerating force, and prevents it from impressing upon the 
NUMBER 28 25 

water new degrees of velocity. This obstacle must therefore 

be the viscidity of the water, which gives rise to two kinds 

of resistance, one, namely, which proceeds from the intestine 

motion of an imperfect fluid, and the other from the natural 

adhesion of its parts to the channel in which it flows. Our 

author, therefore, found it to be a general principle, "that 

when water runs uniformly in any channel, the accelerating 

force which obliges it to run is equal to the sum of all the 

resistances which it experiences, either from its own viscidity, 

or from the friction of its channel." 

The result of this investigation was published in 1779, in 

the first edition of his Principes d'Hydraulique ... . 

Through the influence of M. de Fourcroy, director of the 

Royal Corps of Engineers, the French Minister ordered an 

annual sum to be put at the command of the Chevalier Buat 

[Dubuat], for the purpose of performing a set of experiments 

upon this important subject; and during the years 1780, 

1781, 1782, and 1783, he was constantly occupied with these 

experiments. . . 

In 1783, when M. Buat's experiments were finished, they 

were submitted to the Academy of Sciences through the 

minister of war, and were afterwards published in 1786, 

Hli^J'-W^ gpggjjB^g^^ggjsyBiB S gsw ' I .juuyx MUU 

Piqi I-L-H-II , 

FIGURE 24.—Stream-gaging equipment: a, ca. 1767; b, Michelotti's devices, ca. 1767. 

(From Michelotti, Sperimenti Idraulici.) 
26 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

under the title of Principes d'Hydraulique verifies par un 

grand nombre d'experiences faites par ordre du gouvernment. A third volume of this work was published in 1816 

under the title of Principes d'Hydraulique et de Pyrodynamique.42 

Probably the largest item of laboratory equipment 

which Dubuat had occasion to use during his experiments consisted of a canal, 15 feet wide over which 

he arranged to have a bridge built which just cleared 

the surface of the water. In this canal he could "by 

means of a gate, produce a stream 3 feet deep, with 

a velocity of more than 40 inches per second."

 43

 For 

measuring subsurface velocities he first used a Pitot 

tube, but upon finding it was difficult to read because 

of the tendency of the water in the tubes to oscillate 

continually, he had a substitute made which consisted 

of "a simple tin tube large enough so that we may 

place in it a float which will indicate the elevation of 

the water with greater precision than when it is observed through glass."

 44

 The lower (bent) extremity 

terminated in a plane surface pierced by a small hole 

at its center for diminishing the oscillations in the 

water column. The float supported a slender rod, 

which extended vertically therefrom for facilitating 

observations on an adjacent scale. 

His experience with this device led Dubuat to perform numerous experiments with devices such as 

shown with his portrait in Figure 25. (Note the tiny 

float with its vertical rod in the second drawing from 

the left. By opening just one of the holes therein for 

each observation, he evaluated the pressure distribution across the entire face of the plate.) 

Dubuat's most important laboratory facility for 

measuring surface velocities consisted of a wooden 

paddle wheel (Figure 26) similar to that used by 

Michelotti, but much lighter. Its rotor weighed only 

1114 ounces, and the diameter as measured from the 

center of one plate to the center of the one opposite it, 

was 2 feet. A replica of this paddle wheel is in the 

Smithsonian collection. 

An obituary of David Brewster (1781-1868) that appeared in the 11 April 1868 issue of Harper's Weekly 

described him as "one of the greatest philosophers of 

our age." In addition to his having received numerous awards and academic honors, he held fellowships 

in the Royal Societies of Edinburgh and of London, 

and he was a foreign associate of the French Institute. 

In 1831 he became one of the founders of the British 

Association for the Advancement of Science. No doubt 

the major triumph among his many literary accomplishments was his 22-year editorship of the monumental Edinburgh Encyclopaedia. Tha t encyclopedia 

has especial significance here because its Volume 10 

contains, under the heading "Hydrodynamics," the 

most comprehensive and learned historical review of 

® 

FIGURE 25.—Pierre Louis Georges Dubuat and 

some of his experimental models. (From Rouse and 

Ince, History of Hydraulics; courtesy of Hunter 

Rouse.) 
NUMBER 28 27 

that subject to have been written up to 1832, the time 

of its publication. 

Experimentally, his major achievements were mostly concerned with polarized light and the crystals 

with which it could be produced. While the scientific 

aspects of his work thereon deserve high acclaim, the 

many millions of nonscientific persons who have 

looked into a kaleidoscope (a still popular toy that 

resulted from his investigations) may enjoy knowing 

that Brewster had invented it in 1816. 

The third edition of James Ferguson's multivolume 

work, entitled Lectures on Select Subjects . . ., includes Brewster's notes on the most recent discoveries 

in the arts and sciences,

 45

 and contains the earliest 

description and illustration of Brewster's paddle wheel 

current meter (Figure 27). 

To determine the velocity of water with this meter, 

it would be held so that just the lowermost paddles 

are completely immersed in the water while they faced 

FIGURE 26.—Replica of Dubuat's "moulinet" for measuring 

the surface velocities of water in rivers and canals, ca. 1780. 

(NMHT 317672, photo by A. H. Frazier.) 

FIGURE 27.—Sir David and his paddle wheel type meter. 

(Portrait from Harper's Weekly, // April 1868; drawing 

from Ferguson, Lectures on Select Subjects.) 
28 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

directly into the current. The amount of time required 

for the wheel to make a certain number of revolutions 

would then be determined, and the velocity computed 

therefrom, basing such computations on the assumption that the effective circumference of the wheel (that 

which passes through the center of each of the paddles) will travel at the same speed as the water at that 

location. The number of revolutions could be checked 

by counting the number of threads which the wheel 

had advancd along the threaded axle. 

Although the information contained in Ferguson's 

Lectures does not make it clear as to whether Ferguson or Brewster had conceived of the idea regarding this meter, a book published by Giovambisto 

Masetti about a year later, gives the credit to Brewster.40 

American Innovations 

Beginning in 1830, certain paddle wheels took on 

much larger dimensions and a somewhat different 

function, that of determining the discharge of the 

stream directly. To be sure, the water's average velocity could be determined in the process (by dividing 

the discharge by the cross-sectional area at any location in the stream), but that information ceased to be 

of interest when the total discharge became known. 

These mammoth wheels made their initial appearances in Lowell, Massachusetts, then the fastest growing industrial town in America. There, at the confluence of the Concord and Merrimack rivers, an ideal 

situation existed for developing water power on an 

unprecedented scale. A company called the Proprietors of Locks and Canals on the Merrimack River 

had been formed which offered to sell in package lots, 

entire cotton mills, complete with machinery, dormitories for the employees, and, for a continuing fee, all 

of the water required for its operation. The first mills 

sold under this plan were purchased by the Flamilton 

Company. The earliest thereof went into operation in 

1826; the second in 1827; and the last in 1830. Samuel Batchelder who, up to 1824 had operated a small 

New Hampshire mill, was selected as the Company's 

Agent (Manager), and Ithamar A. Beard (1789-

1871) (Figure 28) formerly the preceptor of an academy at nearby Littleton, was selected for its paymaster. The man who constructed the millwheels for 

these and all of the other early Lowell mills was John 

Dummer. 

FIGURE 28.—Ithamar A. Beard. (From Lowell Historical 

Society collection, Lowell, Massachusetts; photo by A. H. 

Frazier.) 

In 1830, Batchelder decided it was time to determine the overall mechanical efficiency of the Hamilton Mills, and Beard, who had spent much time 

educating himself as a hydraulic and mechanical engineer, was put in charge of that work. Efficiency 

studies require the highest order of accuracy in all of 

the measurements that enter into the problem, and 

this was especially true with respect to the streamflow 

measurements. None of the methods then in vogue 

seemed accurate enough for his purpose, so Beard, 

with the help of John Dummer, developed a special 

paddle wheel for making them so (Figure 29). The 

sides and bottom of the selected measuring section on 

the Hamilton Canal were thereupon lined with heavy 

planking, with a section in the bottom planks carved 

out to match the curvature of the wheel. The wheel 

itself was nineteen feet three inches in diameter, and 

fifteen feet broad. Only the lower one-third of it was 
NUMBER 28 29 

submerged in the water after its installation, and less 

than one-fourth of an inch clearance occurred between the wheel and any of the planks in the lining. 

The wheel was shaped like the paddle wheels on Mississippi River boats except that the compartments between successive paddles were so completely enclosed 

that no water could escape from one compartment 

into the next. Essentially all of the water therefore 

became trapped in the completely filled compartments 

on the wheel as the oncoming water caused it to revolve. The volume of water so trapped during each 

revolution of the wheel was readily computed. By 

timing the number of revolutions of the wheel during 

a given "run," the discharge, in cubic feet per second 

could easily be determined.47 The accuracy of this 

method is second only to that conceived by Hero of 

Alexandria (Figure 3). 

It is of interest to note that the Lowell Courier for 

3 October 1840 (and for several issues thereafter), 

carried an advertisement headed "Ithamar A. Beard, 

Civil Engineer." Among the various items listed therein as services which he performed, were "measuring 

and computing the quantity of water supplied by 

streams." This is believed to be the earliest advertisement offering such services ever to have been published in the United States. 

In 1841, the Proprietors of Locks and Canals decided that it would be to their best interests to know 

the amount of water flowing in the other canals in 

Lowell (Figure 30). They accordingly engaged three 

of the most outstanding American engineers of the 

time to determine by the highest authority, the quantities of water-power drawn by the several mills. They 

were James Fowle Baldwin (1782-1862), George 

FIGURE 29.—Measuring the flow in the Hamilton Canal with Beard's paddle wheel in 1830. 

(Drawn by A. H. Frazier.) 
30 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

jy 

PLA N OF 

CANA L SYSTEM 

PROPRIE-TOR-S OF THE LOCK S AND CANAL a 

MAY 2 9 1941 LOWELL , MAS S 

Note:-

Num\> 

Shouj 

FIGURE 30.-—The canals of Lowell, Massachusetts. 

Washington Whistler (1800-1849), and Charles S. 

Storrow (1809-1904). No finer group of engineers 

had ever previously been brought together for such 

an undertaking. 

James Fowle Baldwin (Figure 31a) was the son 

of Loammi Baldwin, builder of the famous Middlesex 

Canal between Lowell and Boston. Dr. Parsons, in his 

biography of Baldwin, declared that he was surpassed 

by none as a scientific and practical engineer. 

George Washington Whistler (Figure 316), father 

of the artist, has been honored by his fellow engineers 

with a cenotaph at the Greenwood Cemetery in 

Brooklyn, New York, which carries the following inscription : 

This cenotaph is a memorial of the esteem of his friends and 

companions ... . Educated at the U.S. Military Academy, 

he returned from the Army in 1835 and became associated 

with William Gibbs McNeill. They were in their time acknowledged to be at the head of their profession in this 

country. . . . 

In 1842, Whistler was commissioned by Czar Nicholas 

of Russia to take charge of the construction of a 

railroad between St. Petersburg and Moscow. 

Charles S. Storrow (Figure 31c) was perhaps the 

most highly educated hydraulic engineer in the country at that time. After graduating (at the head of his 

class) from Harvard in 1829, he spent several months 

in Loammi Baldwin's extensive engineering library 

in Woburn, Massachusetts, studying the English, 

French, and Italian books on that subject. Then, 

sponsored by Baldwin and the Marquis de Lafayette, 

he gained admission to what was then the world's 

leading engineering college, the Ecole des Ponts et 

Chaussees in Paris. And after completing three years 

of study, he visited England to learn what he could 

about the new Stephenson steam locomotives which 

had recently been constructed there. 

He returned to Boston in April 1832. Construction 

work on the Boston and Lowell Railroad had just 

begun, and he obtained a position with his good 
NUMBER 28 31 

FIGURE 31.—Three eminent engineers who measured the discharge of Lowell canals in 1841: 

a, James Fowle Baldwin; b, George Washington Whistler; c, Charles Storrer Storrow. (a, Courtesy of Steponas Kolupaila; b, from The Illustrated American, 25 May 1895; c, from Engineering News, 16 February 1893.) 

friend, James Fowle Baldwin, the Chief Engineer in 

charge of its construction. When the first trial run 

on this railroad was made between Lowell and Boston, 

Charles Storrow controlled the throttle of the Stephenson locomotive. From 1836 to 1845 he was the agent 

(general manager) of that railroad. During the 

earlier years of his work thereon, much of his spare 

time was devoted to writing his book, A Treatise on 

Water-Works. It was published in 1835 and contained the most authoritative information then available on hydraulics from both European and American 

sources. It is believed to be the first book completely 

devoted to hydraulics ever to have been written by an 

American and published in America. 

Another participant in that canal-measuring project 

was James Francis (1815-1892). He had come to 

Lowell with George Washington Whistler in the early 

1830s at the time Whistler became engaged as Engineer of the Proprietors of Locks and Canals for the 

special purpose of building, in the Lowell Shops, railroad locomotives similar to those built by Stephenson 

in England. Two of those British locomotives were 

brought to Lowell for that particular purpose, a heavy 

and a light model. Francis' first job was to make 

pattern drawings of every one of their cast parts so 

that castings could be produced for use on the American counterparts thereof. When in 1837, Whistler 

left Lowell to finish the earlier work he had started 

on the Providence and Stonington Railroad, Francis 

remained behind. Therefore, he was present at Lowell 

in 1841 when Baldwin, Whistler, and Storrow began 

measuring the discharges in those canals. 

The method these engineers adopted for measuring 

those discharges was identical, in every respect except 

one, to that which the former preceptor of the Littleton Academy, Ithamar A. Beard, had used some ten 

or more years earlier on the Hamilton Canal. The 

exception was found necessary because there were 

considerably larger volumes of water involved than 

could be handled by a single measuring wheel. They 

solved that problem by widening the measuring sections in the canals, and stringing as many sixteenfoot-diameter, ten-foot-wide wheels (with piers between each) as were needed onto a common shaft. 

Seven wheels (the largest number) were used on the 

Western Canal (Figure 32). 

Francis, who had kept the records for this project, 

and who saw to it that the instructions of the Commissioners were carried out, did such a good job 

thereon, that at least two members of the Commission 

recommended that he be placed in charge of the 
32 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

future hydraulic work of the organization. It seems pursued that subject diligently, and ultimately belikely that the experience he acquired in hydraulics coming one of the nation's most highly respected 

on this occasion is largely responsible for his having hydraulic engineers of his generation. 

FIGURE 32.—Discharge measurement of the Western Canal in Lowell, Massachusetts, as conducted in 1841-1842 by Baldwin, Whistler, and Storrow. (Drawn by John Allcott and A. H. 

Frazier.) 
NUMBER 28 33 

TUBING APPLICATIONS 

It has been mentioned previously that adjutages 

extending through the walls of Rome's water-supply 

reservoirs had cross-sectional areas of various multiples of "quinariae," and that such areas were the 

accepted unit of measure for the amount of water 

delivered to a consumer. They represented the earliest 

known use of tubing for measuring the flow of water. 

Without supplementary data, such as the head of 

water above them, and suitable mathematics, this 

"quinaria" method was, to put it mildly, extremely 

erratic. Despite its faults, however, the method persisted to modern times. In fact it was still common 

practice in America during the late 1800s to measure 

flowing water by its modern equivalent, the "square 

inch."

 48 

The Pitot Tube 

During the two thousand years between 300 B.C. 

and A.D. 1700, many studies had been made on how to 

evaluate the flow of water through pipes, orifices, 

sk 

FIGURE 33.—Henri de Pitot and his tube. (Portrait from Rouse and Ince, History of Hydraulicssketch by A. H. Frazier after description by Pitot, "D'Une machine pour mesurer la vitesse des 

eaux courantes") 
34 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

nozzles, etc., but it was not until near the end of that 

period that significant progress was made. In 1732, 

Henri de Pitot (1695-1771) (Figure 33) introduced 

his "tube" which, although it was especially intended 

for use in open channels, became useful in closed conduits. His paper thereon was presented before the 

French Academie Royale des Sciences, Paris, on 12 

November 1732.49 

The original device consisted merely of two slender 

glass tubes mounted side by side onto one of the three 

flat surfaces of a triangularly shaped wooden rod. The 

lower inch or two of the first tube was bent at 90 

degrees to allow it to point directly upstream while the 

main portion thereof was held vertically. The second 

tube was straight throughout its entire length, with 

its lower end at the same level as the bent section of 

the first tube (Figure 33). 

Water entering the open end of the bent tube would 

cause the column of water in that tube to rise above 

the level of the water in the surrounding stream as a 

result of the kinetic energy in that filament of water 

being converted into a pressure head. No corresponding rise would take place in the straight tube. The 

differences in the elevations of water in those two 

tubes accordingly became a function of the velocity 

of the oncoming water. 

Rouse has translated a comment by Pitot about his 

invention as follows: 

The idea of this machine is so simple and natural that the 

moment I conceived it, I ran immediately to the river to 

make a first experiment with a glass tube, and the result 

confirmed completely my anticipation. After this first experiment, I could not imagine that such a simple and at the 

same time very useful thing could escape so many skilled 

people who have written and worked on the motion of 

water.50 

Pitot's method of computing the velocity from the 

readings obtained from his tubes was not entirely like 

that presently in use, but it at least led the way to 

more accurate methods. 

As is true of almost every invention, later experimenters attempt to improve on their predecessor's 

device. For example, Henri P. G. Darcy, circa 1858, 

replaced the straight tube with one on which the 

lower end was bent 90 degrees in the downstream direction. This caused a draw-down to occur in the 

elevation of its column of water, thus doubling the 

reading made on the scale, and reducing probable 

errors entering into such readings. The invention, 

however, still retains its original characteristics and 

Pitot-type tubes are commonly used today in hydraulic 

FIGURE 34.—A Pitot tube intended for use in hydraulic 

laboratories. This model was originally owned by the Proprietors of Locks and Canals of Lowell, Massachusetts. 

(NMHT 314776, Smithsonian photo 74335.) 
NUMBER 28 35 

laboratories (Figure 34) with only slight modifications. The tubes are made of metal, rather than glass. 

Since this material is not transparent, it is impossible 

to read the height of the water column directly; 

flexible tubes are connected from the metal tubes to 

a nearby manometer, from which the readings are 

made with greater facility and accuracy. 

Although current meters of the conventional type 

have been found more practical for use on rivers, 

Pitot tubes have several characteristics that are advantageous for laboratory work and for certain special 

applications. For example, no timing is required in 

connection with an observation; they disturb the 

natural flow of the water much less than most other 

devices; and they are capable of collecting data from 

a much smaller point in the cross-section of the 

stream. 

The Bentzel Velocity Tube 

The Bentzel velocity tube was developed in 1932 

by Carl E. Bentzel, then Research Assistant at the 

U.S. Waterways Experiment Station at Vicksburg, 

Mississippi. Three different models thereof, as manufactured in the 1940s by Leupold and Stevens, Inc., 

are shown in Figure 35a. Like the Darcy model, both 

tubes are bent at their lower ends, with one pointing 

upstream, the other, downstream; but differ in that 

they arc connected at the top so that the water can 

/ 

FIGURE 35.—a, Three models of Bentzel velocity tubes as manufactured in the 1940s by Leupold and Stevens, Inc.; b, sample rating curves for a Bentzel velocity tube. (From Leupold and 

Stevens catalog, ca. 1940) 
36 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

flow upward through the front tube and continue 

downward through the other. At some point along 

that path is a long tapered glass tube within which 

the water-velocity has to vary (inversely) with the 

increase in diameter. A tiny loose float, slightly heavier 

than water, rests at the bottom (narrower) end of 

that tube when the instrument is submerged in still 

water; but when it is in flowing water, the float 

is pushed upward by the oncoming water until a 

balance occurs between the velocity and gravitational 

forces acting on it. Upon its arrival at that resting 

point, the operator reads its height on an adjacent 

scale, and converts that reading into a corresponding 

velocity value obtained from a rating of the instrument. 

Another model based on this same idea has an 

inverted tapered section and a float that is lighter 

than water. The float tends to remain near the top 

of that section until pushed downward by the oncoming water until the equilibrium point is reached. A 

similar rating is needed to convert that point, as read 

on the scale, to the appropriate velocity value. Instruments such as this are discussed at considerable length 

in the chapter on "Variable Aperture Flow Meters" 

in Troskolanski's Hydrometry.51 

A variation on the use of tubing in current meters 

is of historical interest, though it was not in the main 

line of development. On 31 August 1806, Vittorio 

Fossombroni had presented, in behalf of Francesco 

Focacci (fl. 1806), a paper before the Italian Academy of Sciences. It was entitled, "Per Investigare la 

Celerita' Dell'Acque Correnti," and contained a report on the distribution of water velocities in a canal, 

as investigated by Focacci with his two current meters 

(Figure 36). It will be seen that horizontal tubing had 

been used as parts of both models, a unique application for such instruments. 

One (Figure 36a) contained, in the box below the 

a 

4P;^-- V •';•':'-

1/4/ 9, 

' 

^^ 

FIGURE 36.—Focacci's two current meters, 1806: a, balance scales are used to measure the force 

required to open the flap valve within the submerged box; b, pointer enables the operator to 

count and time the revolutions of the rotor within that instrument's box. Bottom of 6 is a vertical-velocity curve of the canal being studied, the earliest known publication of such a curve. 

(From Focacci, "Per Investigare la Celerita' Dell'Acque Correnti," page 396, plates 11, 12.) 
NUMBER 28 37 

water surface, a flap valve that covered the inner end 

of the dowstream tube. Observations were made of 

the minimum weight necessary on the pan of the balance in order to open that valve. A comparison of 

this model with Darcy's version of the Pitot tube is 

of interest in that the weight required to open the 

flap valve (assuming the same size tubing were used) 

would be equal to the difference in weights of the 

two columns of water in the Darcy tube. In Focacci's 

meters, the force is a mechanical one, whereas in the 

other it is a hydraulic one. 

On Focacci's other instrument (Figure 36b), either 

a cup-type or an "S-type" rotor replaced the valve 

mechanism. The axle therof extended upward to the 

top of the apparatus where a pointer was fastened to 

it, which enabled the operator to count (and time) 

its revolutions. 

The Venturi Tube 

In 1797, Giovanni Battista Venturi [J. B. Venturi] 

(1764-1822), Professor of Natural History at Modena, 

published two works, entitled Essai sur les ouvrages 

physico-mathematiques de Leonard de Vinci and 

Experimental Inquiries Concerning the Principle of 

the Lateral Communication of Amotion in Fluids, both 

originally in French. The first brought to public attention the wealth of scientific data (including hydraulics) in Leonardo's notebooks and focused interest 

on his achievements as a scientist, as distinguished 

from that of an artist—an interest that has never since 

abated. 

In 1837, the second of Venturi's publications was 

translated into English by a civil engineer, Thomas 

Tredgold, in his Tracts on Hyraulics. By means of 

laboratory equipment, such as was previously designed 

by the Marquis Giovanni Poleni, Venturi studied the 

manner in which water emerged from a constantly 

filled tank through different types of outlets. One such 

outlet of his own design, to which he had attached 

three manometer tubes, is shown along with Venturi's 

portrait in Figure 38. This particular design of the 

tube bearing his name, allows any volume of water 

flowing through water mains to be metered continuously without using instruments that would interfere 

with the flow. 

Little or no effort was made to adapt Venturi's 

design to any practical apparatus until 1888, when an 

outstanding American hydraulic engineer, Clemens 

Herschel (1842-1930) exploited it to develop a device 

for measuring the amount of water flowing through 

pipes. In recognition of Venturi's experiments, Herschel named his device a "Venturi Tube." Tens, if 

not hundreds, of thousands of Venturi tubes are 

presently in use throughout the world. Herschel was 

Valve 

Rubber coupling 

Glass tube 

FIGURE 37.—The Venturi element (below) and manometer 

from Aggeler's current meter. (Redrawn by A. H. Frazier 

after Aggeler, "Design of a Venturi Type Current Meter.") 
30 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

SUPPLY 

TANK 

VALVLX 

CONSTANT htAu TANK 

ENLARGED VIEW OF ThE VENTURI 

TUbE ON WhICh HE hAU INSTALLED 

THREE MERCURY MANOMETERS 

FIGURE 38.—Giovanni Battista Venturi and schematic of equipment used to test how rapidly 

the various types of outlets would permit filling of the lowermost (discharge) tank. The "winner" (insert) was ultimately known as the "Venturi tube." (Portrait courtesy of Hunter Rouseschematic adapted from Venturi, "Experimental Inquiries.") 
NUMBER 28 39 

awarded a patent (U.S. 381,373) for it on 17 April 

1888. His photograph, and a photograph of the first 

commercial model thereof (built for use in a water 

main in Newark, New Jersey, in 1892), are presented 

in Figure 39. 

Inevitably, someone was bound to devise a current 

meter embodying the principles discovered by Venturi. 

Several of these meters are known, but only the first 

thereof is described here. It was conceived in 1926 by 

one Cecil Aggeler, then an engineering student at the 

University of California. His bachelor's thesis was 

FIGURE 39—Clemens Herschel and his first commercial 

model of the Venturi tube. (Courtesy of Steponas Kolupaila.) 

IvN FOU5J 
40 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 40.—Ralph Leroy Parshall 

and plans of his improved Venturi 

flume. (Portrait courtesy of Steponas Kolupaila; plans from Parshall, "The Improved Venturi 

Flume") 

entitled, "Design of a Venturi Type Current Meter." 

The device consisted on an 8-inch-long cast aluminum 

tube with a Venturi-shaped opening through the center. The hollow space between its inner and outer 

walls was divided into two compartments, one of 

which communicated with the water flowing through 

the throat of the Venturi, the other with the water 

near the entrance thereof. The handle consisted of 

two small-diameter pipes which were connected, respectively, with each of those compartments. Glass 

tubes forming a manometer were fastened onto the 

tops of those pipes, and the water was drawn up to 

the elevation at which readings could be made of die 

relative heights of the two columns by evacuating 

most of the air in those pipes. 

Drawings of that manometer and of the Venturi 

portion of this apparatus, appear in Figure 37. 

Between 1915 and 1926, Victor Mann Cone 

(1883-?), Carl Rohwer (1890-1959), and Ralph 

Leroy Parshall (1881-1959), all irrigation engineers 

of the U.S. Department of Agriculture, and connected more or less consecutively with the Colorado 

Agricultural Experimental Station at Ft. Collins, each 

wrote articles promoting the use of Venturi-type 

flumes for measuring the volume of water flowing in 

irrigation ditches. The most successful of such flumes 

was designed by Parshall (Figure 40) and was described in his article, "The Improved Venturi 

Flume."

 52 

Such flumes have been built in all sizes ranging 

from large permanent concrete or wooden flumes, intended for obtaining continuous records of the flow 

in large canals, to small portable sheet-steel models, 

which some hydrographers carry about like current 

meters for making measurements of very small 

streams. Perhaps the most up-to-date discussion on 

mis subject is in Technical Note No. 117: "Use of 

Weirs and Flumes in Stream Gauging," published in 

1971 by the World Meteorological Organization, a 

specialized agency of the United Nations. 
NUMBER 28 41 

THE LONGITUDE CONTEST 

In 1714, several captains of her Majesty's ships, 

merchants of London, and commanders of merchantmen, presented a petition to the House of Commons, 

claiming that a method for discovering the longitude 

of ships while they were at sea was of extreme importance to Great Britain for the safety of its Navy, its 

merchant ships, and for the improvement of its trade. 

For want of it, they contended, many ships had been 

delayed in their voyages, and many lost; and some 

persons might conceive of suitable methods and 

prove them before the proper judges. A committee 

was accordingly established to consider the subject. 

Among those who presented evidence before that 

committee was Sir Isaac Newton. He suggested that 

large sums of money be offered for the most acceptable solutions. In consequence thereof, Parliament 

passed an Act "for providing a Publick Reward for 

such Person or Persons as shall discover the Longitude 

at Sea. 12 Anne. Stat. 2. cap. 15."

 53

 The amount of 

the reward was graded in amount according to the 

degree of accuracy achieved: 

£10,000 for a method accurate within 1 degree of longitude, 

£15,000 for accuracy within 40 minutes, 

£20,000 for accuracy within 30 minutes.04 

The administration of this statute was entrusted to 

commissioners known as the Board of Longitude. 

De Saumarez' Ships' Logs 

Among those who entered the contest was one Henry De Saumarez (fl. 1715), a member of one of the 

most prominent families on the Island of Guernsey. He 

failed to win any of the prizes, but he did accomplish 

much of historical interest. (No award whatsoever 

was made until 1762, when John Harrison obtained 

the maximum prize for the performance of his No. 

4 marine timepiece on a voyage to Jamaica.) The De 

Saumarez entries consisted of two radically different 

types of ships' logs which he called "Marine Surveyors" (Figure 41). He described them as having been 

"contrived for the mensuration of the way [velocity] 

of a ship in the sea more correctly than by the log or 

any other method used for that purpose."

 55

 Although 

not mentioned in his claims, his logs were also used as 

current meters for measuring the velocity of the water 

flowing in rivers. 

The Log with a Vertical Axis 

There is a practice presently in vogue of dividing 

current meters (and ships' logs) into two major categories, namely those which have vertical axes, and 

those which have horizontal axes. Although De Saumarez' 1715 models bear very little resemblance to their 

modern counterparts, both of them fall within those 

categories.The model with the vertical axis appears 

in Figures 41a, b. Its rotor has four spokes at the ends 

of which he had fastened (by means of hinges) flat 

pallets arranged in such a manner that the oncoming 

water would strike against their broad flat surfaces 

during the "driving" phase of its revolution; but during the remaining portion of that revolution, it would 

strike against only the narrow edge of the pallet. The 

unequal forces thus created would produce the desired 

rotary motion. A replica of this rotor, from the Smithsonian collection of current meters, appears in Figure 42. 

De Saumarez obtained King George I's permission 

to perform experiments with his "machine" on the 

quiet waters of the canal in St. James Park in London. 

There he became satisfied that the rotor would make 

one revolution while the boat traveled a particular 

distance, regardless of the speed at which the boat was 

moving. After having satisfied himself in that respect, 

he adjusted the length of the spokes on the rotor until 

ten feet of travel would produce exactly one complete revolution. 

Whether this principle of operation was borrowed 

from some previous invention, or rediscovered independently by De Saumarez is not known. It is known, 

however, that Edme Mariotte had described an old 

Chinese windmill that operated on much the same 

principle. Figure 43 depicts a model of either an anemometer or a windmill which also operates on this 

principle.56 It may be noted from Figure 41a that a 

large dial constituted an important part of this equipment. De Saumarez explained its purpose as follows: 

A Dial, which being placed anywhere on Board of a Ship, 

will by Correspondence with a small Wheel moving under 

Water, and a little Bell striking with the said Dial, curiously 
42 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

v/?//{\\c//W//S. /cV>'. 

FIGURE 41.—De Saumarez' ships' logs: a, b, vertical-axis model; c, d, horizontal-axis model. 

(From De Saumarez, "III. A Further Account of a New Machine," figures 1-4.) 
NUMBER 28 43 

demonstrate the Geometric Paces, Miles, or Leagues which 

the ship hath run; which being applied in a proper manner, 

will be of little or no Hindrance to the Course or Sailing of 

the Ship. The said Wheel shall turn in any depth of the Sea, 

so that no storm, nor rough Sea, nor the violent Motion of 

the Ship will alter, hinder, nor stop the regular Working 

thereof, but the Swiftness and Slowness of the Ship shall be 

seen and heard by the striking of the little Bell in the said 

Dial." 

Some of the difficulties that De Saumarez encountered in his effort to get the authorities to give consideration to his entries in the "longitude contest" will 

be described later (pp. 46-47). Although that effort 

was not successful, a considerable amount of discussion, including illustrations of his devices, appeared 

later in volumes 33, 34, and 36 of the Philosophical 

Transactions of the Royal Society of London" 

One of the articles {Philosophical Transactions, volume 34) contains several tables showing the speed of 

the currents in the Thames Estuary as the tides ebb 

and flow therein. Two pages of those tables appear in 

Figure 44. De Saumarez obtained the data for those 

tables with his vertical-axis current meter. The tables 

are believed to contain the first of such velocity data 

ever to have been published. 

v^iiu 

FIGURE 42.—Replica of De Saumarez' rotor, which was used 

on his vertical-axis ships' log, ca. 1715. (NMHT 321481, 

Smithsonian photo 75593.) 

FIGURE 43.—A sketch of an instrument that appears in a 

painting entitled, The Paris Academy of Science—A Visit by 

Louis XIV. This device, a forerunner of De Saumarez' ships' 

logs, was doubtless a model of either a windmill or an anemometer. (Redrawn by A. H. Frazier, from Wolf, A History of Science, opposite page 63.) 

Finding a correct designation for the type of rotor 

used on De Saumarez' vertical-axis model has not met 

with too much success. An article by Arthur T. Safford, a former Engineer of the Proprietors of Locks 

and Canals at Lowell, uses an expression, "flutter 

wheel"

 59

 to describe a mill wheel that seemed to 

operate on the same principle. It seems to fit the De 

Saumarez device, but it is not confirmed in the third 

edition of Webster's New International Dictionary. 

The Log with a Horizontal Axis 

One of the difficulties encountered with the verticalaxis equipment was a tendency for weeds and fibers 

to become entangled with the rotor. To overcome diis 
44 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

( h ) 

III. A TABULA R Account, fhewing the Strength 

and gradual Increafe and Decreafe of the Tides of 

Flood and Ebb in the River Thames, as obferv'd 

in Lambeth Reach, off of Mancbefler Stairs, and 

in the Middle of the River, with a new Jnfrrument call'd the Marine Surveyor, on the yth of 

June, 1720, It being then Full Moon, and consequently a Spring Tide. The Movement of the 

Machine 14 Inches under Water. 

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FIGURE 44.—Data compiled by Henry De Saumarez with his vertical-axis ship's log, showing 

the velocities in the Thames Estuary at the ebb and flood tides on 8 June 1720. These are the 

earliest known published data of this nature. (From De Saumarez, "IV. Observations upon the 

Tides in the River Thames," pages 69-70.) 

tendency De Saumarez designed a horizontal axis 

model, which, shaped like a capital "Y" and towed 

through the water by means of a rope connecting the 

lowermost end of the "Y" to the dial aboard the 

ship, shed itself of such unwanted debris. Curved 

metal plates on the outer arms thereof caused the unit 

to revolve about its central axis as it was drawn 

through the water. The curvatures of those plates 

were so adjusted that the speed of its revolution would 

be the same as on the vertical-axis model, namely one 

revolution for every ten feet of travel, so the same dial 

facilities could be used on both models. 

At very low velocities, however, the rotor of the 

horizontal axis model would tend to sink lower and 

lower into the water—the slower the speed, the deeper 

it would sink. This tendency is represented by the 

several positions shown of the rotor in Figure 4It. 

The objection was that as the horizontal angle of the 

rotor increased, it tended to register lower velocities 

than it should. Under most conditions, however, this 

fault was not present. De Saumarez found various 

other practical uses for this equipment, such as to obtain data for a navigation chart showing the locations 

and magnitudes of the velocities occurring in the Eng-
NUMBER 28 45 

f- •— • 

FIGURE 45.—A fleet of ships, ca. 1725, all equipped with De Saumarez' horizontal-axis ships' 

logs, purportedly gathering data on the currents in the English Channel. (Courtesy of the British 

National Maritime Museum.) 

lish Channel. Such a chart, bearing the signature of its 

probable original owner, Captain Bligh of the Bounty, 

has been preserved in the British National Maritime 

Museum, Greenwich. At the top thereof is a painting 

showing a fleet of ships (Figure 45), all equipped 

with "Marine Surveyors," purportedly obtaining data 

for that purpose. A replica of the horizontal-axis rotor 

(Figure 46) is in the Smithsonian collection. 

John Smeaton, the famous British engineer who 

built the noted Eddystone Lighthouse, had not yet 

been born at the time most of the above events were 

taking place. He studied, however, the De Saumarez' 

discussions of his ships' logs in the Philosophical Transactions,60 and proposed what he thought would be a 

major improvement. His paper thereon was read before the Royal Society of London on 4 April 1754.61 

His plan replaced the 27-inch-long Y-shaped rotor 

and its stout cord, with a simple flat piece of brass, 

10 inches long and 2'/2 inches wide, twisted into such 

a shape that it rotated in much the same manner as 

the original rotor. Because of its much smaller dimensions and weight and of the use of a much lighter and 

more slender cord, the drag forces and, consequently, 

the friction in the bearing that had to carry the load 

was greatly reduced—so much so in fact, that a different and much more efficient type of bearing could be 

used. Smeaton tested his apparatus in the serpentine 

river in Hyde Park, London, in much the same manner that De Saumarez had made his original tests. 

A replica of Smeaton's rotor is in the Smithsonian 

collection (Figure 47). 

Apparently this idea did not prove to be as much of 

a success as Smeaton had hoped, because no mention 

of it can be found in later records. 
46 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 46.—Replica of the rotor used on De Saumarez' horizontal-axis ships' logs, ca. 1716. 

(NMHT 321480, photo by A. H. Frazier.) 

FIGURE 47.—Replica of the rotor John Smeaton proposed, ca. 1754, as an improvement over 

the Y-shaped De Saumarez model. (NMHT 321482, photo by A. H. Frazier.) 

Administrative Strategy, 1716 Style 

From what has been reported thus far about De 

Saumarez' ships' logs, it might be assumed that all 

of the problems he had experienced with them were 

of a mechanical nature. Those, however, which he 

encountered with the men concerned with "discovering the longitude" were much more frustrating. In 

1717 he published a 17-page pamphlet setting forth 

his experiences with them.02 It revealed that his discovery had been offered to, and that he had been 

graciously received by, His Majesty, the King, but 

that it had not been "so well encouraged by some of 

those appointed to examine and inquire into the 

same."

 U3

 The King had suggested that he present his 

idea to the Royal Society of London for them to 

evaluate its merits. He accordingly visited Edmund 

Halley, of Halley's Comet fame, who was then Secretary of that society. Halley entertained him at his own 

house "in several friendly conferences" before De 

Saumarez presented his petition, but the Royal Society 

itself did not respond so cordially. It replied in effect 

that: (1) They did not conceive that the decision 

belonged to them; (2) it was not a new discovery; 
NUMBER 28 47 

and (3) the amount it would hinder the ships progress would not be compensated for by its anticipated 

advantages. 

In December 1715, De Saumarez returned again 

to the King who, on this occasion, referred him to the 

Lords Commissioners of the Admiralty. They, as of 

7 January 1716, referred his petition to Sir Isaac 

Newton, who was then President of the Royal Society. 

He, as of 27 January, submitted the following report 

to the Admiralty Office: 

Sir, 

According to the Order of the Lords Commissioners of the 

Admiralty, I have considered the inclosed Proposals of Mr. 

Henry de Saumarez, and discoursed with him upon the same, 

and am humbly of the opinion that by means of the Instrument he hath invented a Reckoning of the distance Sailed by 

a Ship may be kept with less trouble than by the Logg-Line, 

but I am not yet satisfied that the Reckoning will be so 

exact. The Instrument now proposed will keep a Reckoning of the Motion of the Ship with respect to the upper 

part of the Sea Water, but not of the driving of the Ship 

by Currents and Tides, and by the Motion of the upper 

Surface of the Sea caused by Winds, and how far it will keep 

a true Reckoning of the Motion of a Ship side Ways, occasioned by a side Wind, doth not appear to me, and therefore the Logg-Line is not to be laid aside . . the Logg-Line 

alone should be depended upon, until it appears by Experience how far this New Instrument may be trusted. I have 

no Experience in Sea Affairs, nor ever was at Sea, and therefore my Opinion is not to be much Relied on. 

[signed! Is. Newton 

To quote De Saumarez: "The Lords of the Admiralty finding that Sir Isaac declined to give a decisive opinion they were pleased to put it into the 

hands of the Gentlemen of Trinity House."

 63

 After 

due consideration, that corporation prepared a list 

of objections to which De Saumarez responded on 14 

April 1716. After considering that response, they sent 

a report to the Lords Commissioners of the Admiralty, 

dated 8 May, which stated bluntly that "the Corporation is of the opinion the same is wholly impracticable."

 GG 

The Commissioners took no immediate action on 

that report. In fact, De Saumarez could not even get 

a copy of it, or information regarding its contents 

until 8 June. Then, upon finding what it contained, 

he attempted to obtain a patent on it, with the intention of building models at his own expense. He 

was told at the Patent Office, however, that no patent 

could be awarded thereon until the Lord Commissioners of the Admiralty submitted a report to the King, a 

procedure which they appeared reluctant to do. 

On 5 July 1716, De Saumarez petitioned the Commissioners to report to the King in order that he, De 

Saumarez, would not be "hindered" from proceeding 

with the project on a personal basis. They thereupon 

forwarded immediately to the King the report they 

had received from Trinity House, stating that "we 

have nothing further to add thereto."

 G7 

The concluding chapter of De Saumarez' pamphlet 

is headed: "Upon all which, the following observations are humbly offered." The chapter contains only 

five paragraphs, the most succinct of which states in 

effect that if he had been treated as promptly and 

respectfully by the gentlemen of the Trinity House as 

he had been by the Royal Society, he might in less 

than half an hour, have been saved a great deal of 

pains, loss of time, costs, and charges, and returned 

home where he "might have taken other measures." 

De Saumarez did indeed build several models and, as 

already explained, used them for studying the velocities in the Thames Estuary, and for charting those in 

the English Channel. 
-18 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

HORIZONTAL-AXIS METERS 

Early European Developments 

Robert Hooke 

Robert Hooke (1635-1703), the author of Hooke's 

Law of Elasticity, and the first Curator of Experiments at the Royal Society of London, was a man of 

extraordinary talents. Several writers have ranked 

him second only to Leonardo da Vinci insofar as 

inventive ingenuity and conceptual creativity are concerned. Like Leonardo, one of the devices he conceived was intended for measuring the velocity of 

*£i r&JZ *~*~ *ffo s~>j ^ * 

-^H? /& u>y y -• ** 

i*. ~*./*» &•/ ->f 

FIGURE 48.—Hooke's report on a ship's log. (Photocopy from Register of the Royal Society of 

London, volume 6, pages 84-85; courtesy of the Royal Society of London; transcription by A. H. 

Frazier.) 

flowing water. His model was considerably more 

sophisticated than Leonardo's in that it was provided 

with a velocity-sensing mechanical rotor, quite similar 

to those on modern current meters of the horizontalaxis type. He used rotors of that same type in at least 

three different applications: the current meter, a deepsea sounding facility, and on a ship's log which he 

called "A Way-wiser for Sea" (Figure 48).C8 Figure 

49 illustrates the rotor described in Figure 48 as the 

"Vane, Fly, or first mover of the whole." 

A WAY-WISER FOR SEA 

November the 28th, 1683 

I shewed an instrument I had contrived 

and shewed some of the Society about 20 

years since by which the way of a ship 

through the sea might be exactly measured 

as also the velocity of any running Water 

or River and thereby the comparative velocity 

of it in its several parts, by this also the quantity 

of the water vented by any River into the Sea 

or any other River might be found. Tt was 

one part of a way wiser for the Sea. The 

whole Engine being designed to keep a true 

Account not only of the Length of the Run of 

the Ship through the water, but the true Rumb 

or Leeward way, together with all the Jackings 

and workings of the Ship. This part of the Engine 

now shown was the Vane, Fly, or first Mover 

of the whole, feeling as it were & distinguishing 

the several Qualifications of the Ship's Course, 

but was to be regulated by several other 

Additions in the completed Engine which I 

designe shortly to get executed. 
NUMBER 28 49 

A 

FIGURE 49.—Author's reconstruction of rotor that Robert 

Hooke used on his current meter, sounding device, and ship's 

log. (Drawn by A. H. Frazier.) 

Although Hooke's current meter was not responsible for starting the present vogue for horizontal-axis 

meters, it represents the earliest of any devices of that 

type to have been found so far. 

The second meter of the horizontal-axis type to 

have received any appreciable attention, was the one 

previously made by Henry De Saumarez. That too, 

failed to make any lasting impression or attract any 

appreciable number of followers. 

Reinhard Woltman 

Considerably more than a century after Robert 

FIGURE 50.—Replica of the Woltman current meter, ca. 

1790. (NMHT 317671, Smithsonian photo 72259.) 
50 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Hooke produced the first of the horizontal-axis-type 

current meters, Reinhard Woltman (1757-1837), who 

in 1784 was in charge of hydraulic operations at 

Cuxhaven, Germany, produced one that started the 

present vogue (particularly in Europe) of building 

current meters in that manner. It seems unlikely that 

Woltman had known about either the Hooke or the 

De Saumarez meters, but the principle of his rotor, 

and his use of a worm gear arrangement for counting 

the revolutions were very similar to those conceived 

by Hooke. 

In 1790, Woltman published a booklet entitled 

Theorie und Gebrauch des Hydrometrischen Flugels, 

describing his new meter. It explains how he built an 

anemometer, after which he was faced with many 

problems about "rating" (i.e., calibrating) it. After 

several false starts, he finally rated it successfully in 

still water. This gave him the idea that by reducing 

the overall diameter of the rotor from about one meter 

to about one foot, the modified device would serve 

excellently as a water current meter. A replica of this 

water current meter (Figure 50) is presently in the 

Smithsonian collection. 

Julien John Revy 

Julien John Revy (fl. 1870), an Austrian by birth, 

but a resident of England in his later years, was a 

civil engineer of considerable importance. In 1857 he 

was the Director of the Martienson Machine Factory 

in England. Later he became a member of the Austrian Institute of Civil Engineers, and from 1869 to 

1878 (probably the date of his death) he was a member of the British Association for the Advancement 

of Science. In that association's Annual Report for 

1862 is a description of his bold plan for constructing 

a vehicular tunnel, lined with cast iron pipes, beneath 

the English Channel. His most important written work 

was his report on the Hydraulics of Great Rivers: the 

Parana, the Uruguay, and the La Plata Estuary. In 

it he describes how the discharges of those streams 

were measured under his supervision for the British 

Admiralty. In view of the fact that the La Plata 

Estuary alone is at its narrowest over twenty miles 

wide, this must have been the most ambitious stream 

gaging project of all time. 

Many pages of Revy's book are devoted to the faults 

he found with the use of floats for measuring water 

velocities. Current meters, properly handled, he 

claimed, could produce far more accurate results. Before leaving England to start work on that project, 

he had a current meter of his own design built. As 

his work in South America progressed, he kept alert 

for any changes by which it might be improved. His 

final design (arrived at after the project had been 

completed) became a regular stock item with the firm 

of Elliott Bros, (successors to Elliott & Sons) in London, and was listed along with Saxton's meter m 

several editions of their catalog. 

American establishments that purchased at least 

one of the Revy meters were the United States Geological Survey, and the Coast and Geodetic Survey, 

both of which contributed their models to the Smithsonian Institution. A photograph of the one originally 

owned by the Geological Survey is shown in Figure 51. 

Among the innovations Revy introduced in his new 

current meter were the following: 

1. The rotor was so designed that it would have 

no weight when submerged in water. The 2-inch ball 

at the center thereof was filled with air, and had just 

enough buoyancy to make the overall specific gravity 

of the rotor-and-shaft assembly equal to that of water. 

The purpose was to reduce the weight (and consequently the friction) on the bearings which supported 

those parts. 

2. The compartment within which the counting 

gears were located, was filled with clean water, thereby preventing sand, grass, or other materials from 

becoming lodged between the gear teeth and slowing 

down the normal speed of the rotor. 

3. Although Revy used a vertical bar to support the 

meter when using it in relatively shallow water, he 

suspended it from a long horizontal metal bar when 

making velocity measurements in deep water. On such 

occasions it was suspended from a surface vessel by 

means of two wires, one at each end of the vessel supporting the corresponding ends of the horizontal bar. 

(This method has come to be known as the "bi-filar" 

method of suspension.) The arrangement greatly reduced the tendency of the meter to swing like a 

pendulum when operating at great depths, and it 

provided better control of the apparatus while obtaining average velocities by the "integration" method. 

The "integration" method consisted of lowering 

the meter slowly to the bottom, and then raising it to 

the surface at the same speed, with the counting gear 

engaged throughout the entire period of the "run," 

with the time required to make that run, carefully 

determined. The results thus obtained would be the 
NUMBER 28 51 

FIGURE 51.—The Revy current meter, manufactured by Elliott Bros., London, ca. 1874. (NMHT 289646, Smithsonian 

photo 44538-C.) 

average, or integrated velocity throughout the vertical at that point in the stream. It was, as a matter 

of fact, the only method that could be applied with a 

"bi-filar" suspension system, because it was not possible to manipulate a third wire or cord properly for 

engaging or disengaging the counting gear on the 

meter. Point observations could only be obtained with 

this meter when it was suspended from a vertical rod 

or bar, but the maximum depth at which such a bar 

could be handled even when the velocities were moderate was quite limited. 

Revy's current meters—in fact all current meters 

having a similarly geared counting arrangement— 

were eclipsed in popularity with the advent of Henry's 

electrical contact facility, which, as will be described, 

reduced the amount of friction in meters, eliminated 

the need for the operator to raise the meter to where 

he could make "before" and "after" readings of the 

dial for each run, and allowed either "point" or "integrated" observations at any depth without any loss 

of time or any changes in his equipment. 

Joseph Saxton 

Joseph Saxton (1799-1873) the first and most outstanding American to invent a current meter, has in 

the past received perhaps the least attention of any 

such inventors. The story of his life would have been 

a fitting subject for Horatio Alger. He was a descendent of George Sexton who came to America in about 

1663 and lived first near Windsor, Connecticut, and 

then at Westfield, Massachusetts. Subsequent members of his family line lived successively at Huntington, Long Island; Hopewell, New Jersey; Frederick, 

Maryland; and finally, at Huntingdon, Pennsylvania, 

where Joseph was born 22 March 1799. His grandmother was Sarah Harlan of the same family of Harlans from which the two Justices of the United States 

Supreme Court descended, and his brother John was 

the founder of the still-active newspaper, Akron 

(Ohio) Repository, and the grandfather of Ida Saxton McKinley, wife of the martyred President. 

Joseph left school at the age of twelve to begin 

working at his father's nail factory. That work soon 

lost its appeal, and he was apprenticed to a local 

watch-maker. During that apprenticeship, he learned 

the importance of precision workmanship, and the 

subject fascinated him. To constantly improve his 

talent in that field became a primary goal of his 

career. Upon the death of his employer, the nineteenyear-old Joseph left Huntingdon for Philadelphia. 

That city, then the science center of America, seemed 

to offer further opportunities for achieving his goal. 

In 1824, the Franklin Institute in Philadelphia was 

established, and Joseph was among its early members. 

During that same year, the Institute held its first 

public exhibition. Prizes were offered for many classes 

of entries, and one of the local clock dealers entered 

a clock into that competition which Saxton had built 
52 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

for him. The clock was unusual in two special respects: the pallets on its escapement did not have to 

be kept oiled, and it had a unique type of temperature-compensated pendulum. Saxton received the 

highest award offered for such an entry, a silver 

medal.69 

One of the persons who judged that contest was 

Isaiah Lukens, one of Philadelphia's finest mechanics, 

a vice president of the Institute, and perhaps the 

leading manufacturer of tower clocks in the Philadelphia area. He took Saxton into his shop as an associate, and within the next four years they built one 

of the three tower clocks that has occupied Philadelphia's historic Independence Hall. 

In about 1829, Saxton, still searching for opportunities to improve the precision aspects of his work, 

left Philadelphia for a seven-year sojourn in London. 

Just as Philadelphia was the American Mecca for 

those who wished to develop their scientific talents, 

London had become the world Mecca in that respect. 

A possible additional inducement that led Saxton to 

make the trip was the imminent completion there 

of a new museum officially called the "Gallery for the 

Illustration and Encouragement of Practical Science" 

(later abbreviated to the "Adelaide Gallery" because 

of its location at No. 7 Adelaide Street in the Strand). 

Contemporary observers described that gallery as 

both large and elegant—perhaps the most elegant in 

the metropolis (Figure 52). The Gallery had originally been intended to serve as a showplace for exhibiting 

FIGURE 52.—The "Long Room" of the Adelaide Gallery in London. In 1832, Saxton rated his 

current meter in the 70-foot-long tank of water shown in this room. (From the catalog of the 

Adelaide Gallery, May 1836.) 
NUMBER 28 53 

the steam boilers and other inventions of Jacob Perkins (1766-1849), an ingenious Philadelphian who, 

before moving to London in 1819, had been a 

manufacturer of fire engines with Coleman Sellers, 

one of Saxton's close friends. 

Whether Saxton had been assured in advance that 

he would receive work building permanent exhibits 

for that new gallery is not known, but it is well established that promptly after his arrival, he received 

orders to build several of such exhibits. The work was 

performed at his newly established shop at 22 Sussex 

(now Huntley) Street, one block east of Gower, near 

the University College. After the Gallery opened on 

4 June 1832 he gave lectures there concerning those 

and other exhibits. 

During the mid-1830s, while Saxton was still at 

London, Franklin Peale, acting in behalf of the 

United States Mint, placed an order with him to build 

an assay balance. Tha t balance turned out so well 

that several more balances were ordered, and R. M. 

Patterson, then Director of the Philadelphia Mint 

offered him "a good job to begin with" if he would 

return to America and perform work for the Mint. 

Saxton accordingly returned to Philadelphia in 1837, 

and worked for the Mint until 1843, when A. D. 

Bache, then Superintendent of the United States 

Coast Survey, induced him to move to Washington, 

D.C, and assume charge of the Office of Weights and 

Measures, die forerunner of the National Bureau of 

Standards. While holding that position, Saxton finished building and delivering to those States not supplied, a complete set of volumetric, lineal, and 

weight standards, together with a set of balance scales 

(one large, one medium, and one small) for use with 

those standard weights. It would seem that in building 

those precision standards for most of the States, Saxton's goal in life had finally been achieved. He continued in that position until his death, 26 October 

1873. 

Among the many honors Saxton had received during the course of his lifetime, were those of being 

selected a charter member of the National Academy 

of Sciences, and a member of the American Philosophical Society. One of the "State" balances he had 

constructed was sent to the Great Exhibition in London in 1851, for which he was awarded a gold medal. 

Saxton's first efforts in developing current meters 

came as a result of a purchase order from Joseph 

Cubitt—son of the prominent civil engineer William 

Cubitt (1785-1861)—while Saxton was working at the 

Adelaide Gallery in London. Saxton mentions some of 

the subsequent work on the meter in a diary, which 

is preserved in the Smithsonian Archives:70 

May 25, 1832. Saw J. Cubitt and Mr. Cooper [at the Royal 

Institution] who introduced me to Mr. Faraday. 

August 2, 1832. At work at a current meter for Cubitt. 

August 11, 1832. Went to 7 Adelaide Street. Made experiment with the current meter. 

August 21, 1832 7 Adelaide Street.Saw there J. Cubitt and his sisters. 

August 23, 1832. At 22 Sussex Street. Finished current meter 

for Cubitt. 

When, in 1836, the gallery published its first issue 

of The Magazine of Popular Science, it contained an 

illustrated article entitled: "Description of the Current Meter as Recently Improved by Mr. Saxton." A 

reproduction of those illustrations appears in Figure 

53. As may be seen in that figure, the rotor on this 

meter consisted of a flat piece of brass twisted into 

such a shape as to cause it to revolve when water 

moved through it. Whenever the "engaging" cord was 

held taut, the rotating shaft would cause the counting wheel to start operating. Saxton "rated" his current meter in the 70-foot-long water tank in the Long 

Room of the Adelaide Gallery (Figure 52). The 

rating consisted of increasing or decreasing the 

amount of twist in the rotor until it would make exactly one revolution for every foot the meter traveled 

through the still water in that long tank. 

In this connection it should perhaps be mentioned 

that Saxton, Charles Wheatstone (famed for the 

"Wheatstone Bridge" for making electrical measurements), together with a John Martin and two other 

persons, made a measurement of the flow of the Colne 

River at Denham Point near London with Saxton's 

current meter on 22 June 1834, in accordance with 

a plan proposed by Martin for improving London's 

water supply.71 

During the 1830s there existed in London a firm 

by the name of Watkins and Hill that sold scientific 

instruments and laboratory equipment. After Saxton 

arrived in London, their catalogs listed several articles that Saxton had designed and furnished to 

them. Saxton's current meter, however, does not appear in any of their few surviving catalogs. Nevertheless when that firm was taken over by the Elliott 

organization in the 1850s, it was listed in the catalog 

that showed the combined products of the two firms. 

An illustration of the meter also appeared in 1858 as 

"Fig. 129A" in the first edition of W. Davis Haskoll's 

book entitled The Practice of Engineering Field 
54 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

a 

R 

f 4 

. i. ~. * • 

1 ' -

• 

:[ 

FIGURE 53.—Joseph Saxton's water current meter: a, top view; b, side and end views. 

(From Adelaide Gallery, "Description of the Current Meter.") 

Work, together with the following statement: "Elliott's [i.e., Saxton's] Current Meter is a most useful 

instrument for ascertaining velocities, either a few 

inches below the surface, at the bottom, or at any 

depth between."

 72 

In any event, the Proprietors of Locks and Canals 

of Lowell, Massachusetts, were among those who acquired one of Elliott's models of the Saxton meters, 

and in 1956 they contributed it to the Smithsonian 

Institution (Figure 54). 

Although Saxton's meter was never listed in any 

American manufacturer's catalog, quite a number of 

them were custom-built here, and they made appearances in several unexpected places. One such appearance is mentioned in the Humphreys and Abbot famous Report Upon the Physics and Hydraulics of the 

Mississippi River.73 Saxton's was the only current 

meter used in that study, whereas over 99 percent of 

the other observations were made with floats. On another occasion, Professor William P. Trowbridge of 

the U.S. Coast Survey

 74

 attached two Saxton current 

meters (both pointing downward) onto a device he 

had invented in 1857 for sounding the depths of the 

ocean in places too deep to be reached with the conventional line and weight. Their function was to 

measure the depth as the device descended to the bottom. Upon arriving there, a detent locked their motion, so that upon raising the assembly, the operator 

could observe on the counting wheels the number of 

rotations made by their rotors and thereby compute 

the ocean's depth. 

Prior to the Civil War, Humphreys, Trowbridge, 

and Saxton were fellow employees in the U.S. Coast 

Survey, and were well acquainted. There seems little 

doubt but that all of these meters were built in the 

instrument shop of the Office of Weights and Measures, where the lineal, volumetric, and weight standards had been built under Saxton's supervision for 
NUMBER 28 55 

FIGURE 54.—Saxton's current meter as manufactured by Elliott & Sons, London. 

{NMHT 314772, Smithsonian photo 44536-A.) 

FIGURE 55.—The "Abbot" meter. (From Payson, "Current-Observations 

in San Francisco Harbor, California.") 
56 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

the American States. 

Perhaps the most unexpected circumstances under 

which Saxton current meters were used occurred in 

1877 and 1878 when the federal government made a 

study of the hydraulic aspects of San Francisco Bay.75 

In his report on that study, Lt. A. H. Payson called 

them "Abbot" current meters. General Henry Larcom Abbot had provided them for use on that study 

after having redesigned certain parts to overcome the 

problems caused by using them in sea water. A drawing of one of these meters, as it appears in Payson's 

report, is shown in Figure 55. 

Current meters were not accepted without controversy, even by those who were the forerunners in 

hydraulic engineering. In Humphreys' and Abbot's 

report on the Mississippi River, it had been stated that 

double floats were superior to any other device for 

measuring water velocities.70 In 1868, when Daniel 

Farrand Henry of the U.S. Lake Survey ventured to 

invent and use current meters for measuring the outflow of the Great Lakes, both Henry and his superior, 

General William F. Raynolds were severely disciplined 

for having used meters for that purpose.77 Henry Abbott, the co-author of Humphreys' Mississippi River 

report, expressed himself as follows in a subsequent 

report: "In my opinion, . . . instruments of this class 

are pretty toys, which have contributed more to retard 

the progress of discovery in the science of river hydraulics than any other one cause,"

 78

 and for many 

years thereafter, Abbot and Henry debated this subject bitterly. 

One of the major improvements Henry had made 

on current meters was the electrical facility for counting the revolutions made by the rotor. After having 

first installed such facilities on his Saxton current 

meter, and finding them to work successfully, he next 

applied them to the cup-type meters of his own invention, the latter of which received favorable attention in several European technical magazines. 

In view of Abbot's opposition to the use of any current meters, the advent of the "Abbot" meter at San 

Francisco ten years after his objections were published, must have surprised many of those familiar 

with the acrimonious Abbot-Henry debates. Moreover, Abbot's meter consisted essentially of a Saxton 

meter furnished with an electrical contact, just as 

Henry had originally changed it. The only difference 

was that Abbot had enclosed the contact facilities 

within an oil-filled brass compartment intended to 

exclude die salt water from the area where the contacts took place. 

If Abbot ever felt that his action represented any 

softening of his attitude toward Henry's work, he 

never admitted it publicly. 

The Baumgarten Meter 

Table I in Professor Kolupaila's Bibliography of 

Hydrometry is a list of "Significant Hydrometric Measurements in the 19th Century." The third entry 

refers to measurements obtained of the Tiber River 

in Italy by Giuseppi Venturoli (1784-1846) starting 

in 1821, and the seventh entry refers to those obtained 

of the Garonne River in southern France by Andre 

Gustave Adolphe Baumgarten (1808-1856) starting 

in 1838. Venturoli was a professor of mathematics at 

the University of Bologna, and Baumgarten was an 

engineer at the Ponts et Chausees in Paris. In both 

Venturoli's book, Elementi di Mechanica e Hydraulica, and Baumgarten's article, "Sur le moulinet de 

Woltmann . . . , " 79 the same type of current meter is 

illustrated (Figure 56a, b). Venturoli did not identify 

the person who designed that meter, but Baumgarten 

made a special point of crediting Woltman. It was, in 

fact, an improvement over the original Woltman 

meter (cf. Figures 50 and 56), and Woltman probably 

had nothing to do with the changes that had been 

made. Tha t generous gesture, however, has resulted in 

numerous subsequent writers of modern hydraulic 

text books maintaining the same designation for this 

type of meter, i.e., Woltman meter, whenever they 

used Baumgarten's illustration. 

In any event, unless Venturoli himself conceived 

this improved model, the name of the person responsible for it has not received the credit due him. By 

1847, this meter became a regularly manufactured 

product of the firm of Lerebours et Secretan of Paris. 

Copies of several of their catalogs illustrating it among 

their hydraulic instruments still exist. The Proprietors 

of Locks and Canals at Lowell, Massachusetts, purchased from diem a meter of this type, which in 1956 

they contributed to the Smithsonian Institution 

(Figure 56c). 

This meter was just the first of two with which 

Baumgarten had become concerned. While using it, 

he realized that the relatively small pallets (or vanes) 

on this meter could utilize only a small portion of the 

total driving force present within the circle defined by 

their rotation; if the total force available within that 
NUMBER 28 57 

ttJ 

www o 

U b 

FIGURE 56.—Woltman current nreters: a, Venturoli's version, 1818; b, Baumgarten's drawing, 

1847; c, improved model manufactured by Lerebours et Secretan, Paris, (a, Redrawn by A. H. 

Frazier after Venturoli, Elementi di Mechanica e Hydraulica; b, from Baumgarten, "Sur le 

moulinet de Woltmann"; c, NMHT 314769, Smithsonian photo 73-777.) 

circle were made use of, the driving force would be 

much enhanced. In fact, a rotor of much smaller overall dimensions probably could be used without any sacrifice of power. He accordingly suggested that change 

to his supervisor, Jean Victor Poncelet (member of 

the French Academy of Sciences), who assigned a 

Paris instrument-maker named Conte to work with 

Baumgarten to produce a new meter with at least two 

rotors of the suggested type. Each rotor was to have 

four helicoidal blades surrounded by a wide metal 

band for strengthening the assembly. Each blade extended to the axle, and occupied one-fourth of the 

projected area within the ring. The rotors differed 

however, in that they had pitches of 0.08 and 0.12 

meters, respectively. Either could be installed on the 

same meter, so that their performances could be compared under identical operating circumstances. The 

meter was completed late in 1846. During the months 
58 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 57.—Baumgarten's current meter, manufactured by Secretan of Paris, ca. 1846. 

(NMHT 314773, Smithsonian photo 44536.) 

that followed, Baumgarten performed his tests on it 

while conducting his studies on the Garonne River. 

Illustrations of it appeared in Secretan's catalog (successors to Lerebours et Secretan—Marc Lerebours 

having died in 1867) for numerous years. Baumgarten died a suicide in 1859. 

Two of the 1846 models were to contribute to hydraulic history in America. The Proprietors of Locks 

and Canals of Lowell purchased one of them (Figure 

57), and Clemens Herschel, the noted hydraulic engineer who often did work for those Proprietors, purchased the other. 

In the early 1870s, two major hydraulic projects 

were being undertaken in the northeastern United 

States. General Theodore Grenville Ellis (1829-1883), 

a member of the Corps of Engineers. U.S. Army, under the Chief of Engincrs, A. A. Humphreys, had 

been placed in charge of a study aimed at improving 

the Connecticut River for navigation, and Alphonse 

Fteley (1837-1903) had been named the resident engineer in charge of the construction of the new water 

supply for Boston from the Sudbury River. Baumgarten current meters served a useful purpose on both of 

those projects. 

In about 1870, when General Ellis began his work 

on the Connecticut, he purchased the Baumgarten 

current meter from Clemens Herschel. In view of 

General Humphrey's strong opposition to the use of 

such instruments, it seems likely that any publicity 

regarding its purchase would have been kept to a minimum. In fact, when Ellis wrote his official report on 

the project, and had to admit having made use of 

such a current meter, he spent several pages explaining his reasons for having done so.80

 His arguments 

were so convincing that Humphrey credited him -with 

having used good judgment, and the f?an against the 

Army's use of current meters was thereupon lifted. 

Before Ellis could make any use of the Baumgarten 

current meter, it had to be rated to establish an equation showing the relationship between the number of 

feet per second (f), at which the water was flowing, 

and the number of revolutions per second (n), performed by the rotor. Ellis made one such rating in 

1870, and another in 1874, and found fhat for velocities between 0.7 and 9.0 feet per second that equation was: f = 5/12 n + 0.25. On the same occasions, 

however, he learned that the meter "ceased to register 

accurately and in exact conformity with the formula 

below 0.7 feet per second.''

 81 

Ellis made considerable use of this meter during the 

first four years of his work on the Connecticut River, 

but its lack of precision in the lower velocity range, 

caused him to explore other possibilities. By June 1874 

he had designed a vertical-axis cup-type current meter 

similar (but smaller) to that designed several years 

earlier by Daniel Farrand Henry of the U.S. LaTce 

Survey. The new "Ellis" meter was so superior to 

Baumgarten's model that he performed the remaining measurements of his project with the new one. 
NUMBER 28 59 

FIGURE 58.—The principle hydraulic engineers who constructed the Sudbury River watersupply system for Boston and designed many other outstanding hydraulic projects in America: 

a, Alphonse Fteley; b, Frederick Pike Stearns. 

The "Ellis" meter will be discussed shortly. The 

point to be observed here is that the Baumgarten 

meter played an important part in overcoming the 

Corps of Engineer's prejudice against the use of current meters, and it contributed to the development of 

Ellis' considerably better instrument here in America. 

Work on the Boston water-supply project began in 

1873, just a short while before Ellis stopped using the 

Baumgarten meter. Alphonse Fteley (Figure 58a), 

who was the resident engineer in charge of the project, soon found that he too needed a current meter. 

The need was met by borrowing the Baumgarten 

meter from Ellis, and having a local instrument manufacturer, Buff and Berger, make a copy of it (Figure 

63a). The new model differed from the original in 

two respects: its rotor was slightly larger in diameter, 

with more blades having a longer pitch; and the 

facility for disengaging the counting wheels was reversed in that the spring that formerly kept those 

wheels disengaged (until activated by a pull on the 

operating cord) now kept them engaged during the 

periods of operation. It had been noted while in Ellis' 

possession, that the force applied to the cord was 

sometimes great enough to damage the gears. Such 

an effect could not take place if the spring were used 

to keep those gears in mesh, and the cord used only 

for disengaging them. A drawing of that new current 

meter (Figure 63a) appeared in an article by Frederick P. Stearns, Fteley's principal assistant (Figure 

58fc). 

Fteley and his assistants used this meter for several 

years for measuring the flow of the Sudbury River 

and nearby streams. He also found it satisfactory in 

most respects, except for measuring low velocities. 

Like General Ellis, he thereupon developed a new 

meter. 

About the only part of the new meter which resembled any part of Baumgarten's was the rotor, and 

even that was modified. It had several more vanes, all 

with a longer pitch. The axle extended completely 

through die rotor, and was supported by both front 

and rear bearings. The counting wheels were smaller 

in diameter, and arranged to face upward, so that the 

operator could read them without lifting the meter 

completely out of the water. The first models of this 

meter were manufactured by Buff and Berger. 
60 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

It should be noted that the Fteley meter (often referred to as the "Fteley-Stearns Meter" because 

Stearns assisted in its development) was of a specialpurpose type. Its major purpose was to measure, 

through a manhole, the velocities occurring in underground conduits which had been built for conducting 

water from the Sudbury River to Boston. It was 

always suspended from a rod. The operator could 

therefore easily maintain its proper orientation which 

eliminated the need for a tailpiece. While that feature 

admirably served the need on this water-supply project, it restricted the use of the meter to relatively shallow streams and conduits where cable-suspension facilities (and tailpieces) were not essential. 

Practically no changes were made in the design of 

the Fteley-Stearns meters for over 25 years. In 1911, 

however, while still an Assistant Engineer of the Proprietors of Locks and Canals at Lowell, Massachusetts, 

Arthur T. Safford (1867-1951) proposed changing 

the design of that meter by decreasing the number of 

vanes thereon from 8 to 6, increasing the diameter of 

the rotor from V/i to 5 inches, and making the frame 

larger and somewhat stronger. 

FIGURE 59.—A current meter contributed to the Smithsonian 

Institution by the Proprietors of Locks and Canals of Lowell, 

Massachusetts, which may be an experimental model designed by A. T. Safford. (NMHT 314771, Smithsonian photo 

44536-C.) 

FIGURE 60.—Comparison of the original (a) and improved 

(b) Fteley-Stearns current meters as presented by Hughes 

and Safford, A Treatise on Hydraulics, 1916. 

FIGURE 61.—A Fteley-Stearns current meter manufactured 

by C. L. Berger & Sons, Boston. (NMHT 330410, Smithsonian photo 75409.) 
NUMBER 28 61 

Although its record is not entirely clear, there is in 

the Smithsonian collection, a current meter (Figure 

59) that came from the Proprietors of Locks and 

Canals, which has about the same type of rotor that 

Safford had advocated. Its counting gears, however, 

are located in a rather bulky metal box behind the 

rotor with a glass window at one side for observing 

the readings. Since no other current meters like it are 

known to exist, this might well have been an experimental model which Safford had designed while developing the "improved" instrument. The final model 

was provided with a much smaller counting wheel 

box, which faced upward and was located in a far 

more convenient location. Figure 60 shows a comparison between the old Fteley-Stearns and the new 

Safford models. 

In later models, the counting wheels were eliminated entirely in favor of the electrical contact method 

as conceived by Daniel Farrand Henry. While all this 

had been taking place, the firm that had constructed 

the original Fteley-Stearns meter, Buff and Berger, 

had dissolved its partnership, and both members 

thereof set up separate businesses, but both of those 

separate firms continued manufacturing all of the 

models in which Fteley, Stearns, and Safford were 

involved. One of those later models, as manufactured 

by C. L. Berger & Sons, was eventually added to the 

Smithsonian collection (Figure 61). 

From all these events it is apparent that the Baumgarten current meter that Clemens Herschel sold to 

General Ellis produced a truly notable impact on the 

design of such instruments in America. This, however, 

does not mark the end of the saga. The story of the 

meter shown in Figure 57—the one that the Proprietors of Locks and Canals purchased at the same time 

that Herschel obtained his—also deserves attention. 

James Francis, who at that time was the Chief Engineer of Locks and Canals of Lowell, Massachusetts, 

was favorably impressed with the Baumgarten current 

meter although he too recognized as a deficiency its 

failure to operate satisfactorily at low water velocities. 

In the belief that much of that deficiency could be 

remedied by improvements in the bearings, he requested Herschel to take the matter up with George 

Louis Buff (1839-1923), the senior member of the 

Buff and Berger firm in Boston, to see what he 

thought could be accomplished in that respect. Buff 

was born in the university city of Geissen, Germany, 

FIGURE 62.—Three experimental rotors manufactured by Buff and Berger, Boston, ca. 1876, 

for trial on the new "Herschel" meter, an American version of the Baumgarten meter (NMHT 

314766, 314767, 314768; Smithsonian photo 44536-B.) 
62 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

and was of the old German school of fine instrument 

makers. 

A transcription of the first letter, dated 20 September 1876, that Herschel wrote to Francis on this subject and which had been preserved in the Office of the 

Proprietors of Lock and Canals, follows: 

To James B. Francis 

Civil Engineer, 

Agt. Props. Locks & Canals 

Lowell, Massachusetts. 

From Office of Clemens Herschel 

Civil and Hydraulic Engineer, 

66 State Street, Boston, 

Sept. 20, 1876. 

Dear Sir: 

I have not exactly got Mr. Buff started on making your 

new current meter, but am gradually starting him. My idea 

is to make the instrument of certain defined dimensions & 

mathematical shapes or forms throughout, so that from its 

description, another just like it may be made elsewhere. If I 

can induce someone to order another instrument, we can 

then try whether two instruments made exactly alike (the 

word "exactly" being used in the common mechanic's sense 

of that term) will register velocities alike, or how near alike. 

Now, to the end of making the new instrument such that it 

can be regarded as a model, and, (if two instruments made 

alike, register alike) to the end that our experiments may be 

considered valid for many other like instruments, it has 

occurred to me that it might be advisable to make the new 

current meter in the metric dimensions. Of course, it can be 

rated to any desired measures & used in the same; the article itself only, to be bounded & described metrically. How 

does this idea strike you? Mr. Buff is neutral in the matter, 

and as for me, I have no decided wish either way; perhaps 

this is being neutral also. Will you please decide. 

When we get a sketch of the proposed instrument I will 

show it to you before starting on the construction of the 

instrument. The model for the propeller wheel is to be 

begun in July, but I will stop it until I hear from you. It is 

to be a true helicoid, cut into 4 equal parts, and placed 

around the axis so as to occupy the V* height of the whole 

helicoid, a mathematical figure that can be reproduced even 

should the model be lost. 

Truly yours, 

[signed] Clemens Herschel 

In a second letter, dated 22 September 1876, that 

Herschel wrote to Francis, he transmitted a list of 

ideas he had in mind for the new meter. 

General Plan for Current Meter 

1. The propeller wheel to be abt. 5" diam., each V4 part of 

a true helicoid of 5" rise. This makes the wheel VA" 

deep. A guard rim at periphery. The wheel to be set 

well forward of the rest of the instrument. 

2. The two journals to be agate- the collar & the end-pivot 

of German silver. 

3. The propeller wheel and the axis that turns with it} to 

4. 

be without weight in water; this to be attained by making the axis hollow. 

The counter-wheels, throw-in & out gear, & general 

frame, like the one owned by Locks & Canals & the one 

once owned by C. Herschel, now by Genl. Ellis. 

5. The frame to be a closed box, however, the side next the 

figured side of the counter wheels of glass, and so arranged that it may be filled with water. 

6. The spindle large enough to hold a 2Vz inch rod. 

7. All the dimensions of the instrument to be some even 

measure, & the shapes mathematical shapes, so that the 

instrument can be reproduced from its description. 

(2 & 3, I should expect, will about anhilate [sic] the friction 

at the axis. 5 causes all the parts to move always in the 

same medium, whether working in clean or gritty water, 

etc.) 

Sept. 22, 1876 

FIGURE 63.—Current meters in the 1885 catalog of Buff and 

Berger, Boston, probably the first American firm to list such 

meters in its catalog: a, copy of Baumgarten meter requested by Ellis for the Boston water-supply project; b, c meters 

made for Proprietors of Locks and Canals, Lowell, Massachusetts; d, Ellis' cup type meter. 
NUMBER 28 63 

In connection with this development project, three 

different experimental rotors were built. Two of them 

had four helicoidal blades each, and one had five of 

them. One had just a plain metal band surrounding 

the blades, the other two had flat, hermetically sealed 

tubes in that location. Those tubes, being filled with 

air like the balls on the Revy current meters, caused 

the rotors to have the same weight as water, thereby 

reducing the pressure (and consequently the friction) 

on the bearings. The two rotors that had the 

"weightless" feature were six inches in diameter, 

whereas the one having just a plain band around it, 

was five inches in diameter. All three of these rotors 

have been preserved, and arc in the Smithsonian collection (Figure 62). 

The final outcome of all the experiments and negotiations was that two models were produced. Both had 

agate main bearings. One (Figure 63b) continued 

the original use of counting wheels (but they were 

inclosed within a glass-covered box filled with clean 

water to keep out grit and fibers) ; the other (Figure 

63c) used the electrical-contact system which eliminated the counting gears. An article, entitled "Current 

Meter—from advance sheets of Buff and Berger*s enlarged catalog of Improved Engineer's Instruments," 

appeared in the 25 April 1878 issue of Engineering 

News and stated in reference to these meters that 

careful experiments were made at Lowell, in the summer of 

1877 under the direction of James B. Francis, Engineer of 

"The Proprietors of Locks and Canals on Merrimac River" 

and warrant to say that velocities as low as 0.17 of a foot 

per second can be measured. 

To have reduced the minimum velocity at which the 

meter could operate dependably from 0.70 to 0.17 

feet per second was indeed an important accomplishment. It is believed that Buff and Berger is the first 

American firm ever to have listed current meters in 

its catalogs. 

Other American Models 

Hall's Current Meters 

While the Baumgarten current meter was making 

hydrometric history in the northeastern corner of the 

United States, something of a similar nature (although not as extensive) was occurring in the Far 

West. It began in 1877 and 1878 when the Saxton 

current meter (as modified by General Abbot) had 

been used by the Corps of Engineers while making a 

FIGURE 64.—William Hammond Hall, California's first 

State Engineer. (Courtesy of Mrs. Hosea Blair.) 

study of the currents in San Francisco Bay (see Figure 55). During the latter of those two years, William 

Hammond Hall (1846-1934) became California's first 

State Engineer (Figure 64), during which time he is 

most remembered for his conception and creation 

of San Francisco's magnificent Golden Gate Park. 

When the State legislature established a new Department of Engineering as of 29 March 1878, it stipulated that its primary objective should be to ascertain 

why the Sacramento and San Joaquin rivers flooded 

so frequently. California thereupon became the first 

State in the Union to engage in organized streamgaging activities, preceding the federal government 

by all of ten years in that respect. 

As State Engineer, William Hammond Hall was 

immediately faced with the problem of obtaining 

equipment with which to measure the flow of those 

rivers. The solution thereto was ultimately published 

in a report/ 3 which stated in part: "Six current meters were used by the Department. Two of these were 

the property of the Engineer Corps of the U.S. Army, 

and four others were closely patterned after these 

two." From the description of those meters which fol-
64 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

lowed, there can be no doubt that the two Corps of 

Engineers' meters were of the same type (if not the 

identical instruments) as had been used in San Francisco Bay. With respect to the other four meters (undoubtedly built in California), the writer added: 

"The blades of the wheels should be heavier, and their 

upper and front edges should be made sufficiently conical in outline to ward off floating leaves, twigs, 

etc."

 84 

Later in his career, Hall was employed in the Irrigation Survey of the U.S. Geological Survey. A few of 

his current meters were acquired by that Survey for 

use in its early stream-gaging program. Two of those 

meters—one intended to be used while suspended 

from a rod, the other while suspended from a cable— 

were preserved and in time transferred by the Geological Survey to the Smithsonian Institution (Figure 

65). 

The Haskell Current Meter 

Amost every hydrographer worth his salt, who had 

used a current meter designed by someone else, seems 

to have come up with a better design of his own. So 

it was with Eugene Elwin Haskell (1855-1933) (Figure 66). He graduated from Cornell University in 

1879. His earliest job experiences were in Detroit as 

a recorder for the Survey of the Northern and Northwestern Lakes (now more commonly referred to as 

the "U.S. Lake Survey"), and in charge of a party 

of engineers employed by the Mississippi River ComO 

FIGURE 65.—Hall's current meters designed ca. 1880: a, meter for use with rod suspension 

(NMHT 289639, Smithsonian photo 445537-F); b, meter for use with cable suspension (NMHT 

289640, Smithsonian photo 44537-G). 
NUMBER 28 65 

FIGURE 66.—Eugene Elwin Haskell, Dean, College of Engineering, Cornell University, 1906-1921. (Courtesy of Cornell University.) 

mission, measuring the discharge of the Mississippi 

River at Point Pleasant, Missouri. 

During the period 1885 to 1893, Haskell was employed in the U.S. Coast and Geodetic Survey. One 

of his first assignments there was to plot, under Professor Henry Mitchell's supervision, the direction and 

magnitudes of the currents in New York Harbor. It 

was while he was so employed that he invented his 

current meter. It differed from the cup-type meters 

then in vogue on the Mississippi River in that his 

was of the earlier horizontal-axis, screw-type design, 

and it included a direction-indicating facility. To 

quote Haskell's Reminiscences: 

Mr. E. S. Ritchie, inventor of the liquid compass, had solved 

the problem of reading a distant compass electrically; accordingly I joined forces with him and a direction current 

meter was the result. This was put in use in the Spring of 

1886 on the New York Harbor work.85 

Haskell later used this current meter in a study of 

the currents off the Florida coast and in the Gulf 

Stream. As of 12 June 1888, U.S. Patent No. 384362 

was awarded to him for it (Figure 67). For many 

years thereafter, the E. S. Ritchie firm in Brookline, 

Massachusetts, manufactured them. 

In the course of his eventful and eminent career, 

Haskell became a member of several important reFIGURE 67.—The Ritchie-Haskell direction-indicating current meter. 

(CouUesy of U.S. Geological Survey.) 
66 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

gional, national, and international commissions dealing with hydraulics. In 1906 he became Dean of the 

College of Engineering at his old alma mater, Cornell 

University, a position he held until his retirement in 

1921. 

U.S. Irrigation Survey Models 

On 2 October 1888, Congress passed a Sundry Civil 

Bill appropriating $100,000 for studies concerned with 

irrigating the lands west of the 100th meridian. The 

new agency was called die United States Irrigation 

Survey, and made a part of the Geological Survey in 

the Department of the Interior. One of its first objectives was to establish a temporary camp of instruction 

on the Rio Grande at Embudo, New Mexico, for 

training a group of young engineers in the art of gaging streams.86 

At the time that bill was passed, the Geological Survey did not have any current meters or other streamgaging equipment with which that group could gain 

the desired experience. John Wesley Powell, then Director of the Survey, appealed to some of the other 

likely federal agencies for the loan of any such instruments that they might have to spare. While waiting for those agencies to respond, the group made 

measurements with different types of floats fashioned 

from locally available materials, and also by running 

levels down the stream to determine its slope, and 

computing the discharge from existing formulas. 

Powell's appeal eventually met with one lone response. The Navy Department shipped to the camp a 

36-inch-long, cable-suspended Ritchie-Haskell direction-indicating current meter, such as shown in Figure 

67. It, however, turned out to be far too large and 

much too cumbersome for use in the shallow waters 

which normally occur at Embudo during the winter 

seasons. This being the only current meter available 

up to this point, they immediately set about redesigning it in a manner that would better serve their needs. 

One of the group was sent with the resulting plans to 

an instrument-maker in Denver, and within a short 

period of time a much smaller and more convenient 

model, similar to that shown in Figure 68 (but arranged for rod suspension), was produced and placed 

in service. 

During the years that followed, almost a dozen 

variations from the Irrigation Survey's (and William 

Hammond Hall's) models were tested. Four of them 

along with the direction-indicating meter, were added 

to E. S. Ritchie and Sons' line. Two of diose four 

models (Figures 68 and 69) are now in the Smithsonian collection. The one shown in Figure 69 was 

listed in the catalogs as "Current Meter 'B' complete 

with lead weight and extra wheel." The rotors or 

FIGURE 68.—A variation of the Haskell current meter as conceived in 1888-1889 by engineers 

of the U.S. Irrigation Survey. (NMHT 248697, Smithsonian photo 44537-B.) 
NUMBER 28 67 

FIGURE 69.—Current Meter B (an early variation of the Haskell current meter) with sounding 

weight, manufactured by E. S. Ritchie & Sons, Brookline, Massachusetts, ca. 1900. (NMHT 

316590, Smithsonian photo 72237.) 

"wheels" then in use had diameters ranging from Th 

inches down to 5!/2 inches. Some had a high (screw) 

pitch, others had a low pitch. The latter would operate better in the lower velocities, although they ceased 

to perform reliably below 0.5 foot per second. When 

operating in velocities above say four feet per second, 

they revolved so rapidly that their revolutions could 

not be counted accurately. The slower turning, higher 

pitched wheels would then be installed on the meters. 

In 1889, the activities of the Irrigation Survey were 

practically brought to an end, but in 1904, the Water 

Resources Branch of the Geological Survey was officially activated, and stream-gaging operations were revived not only in the area west of the 100th meridian, 

but throughout the entire United States. This work is 

still being carried on. At present the more recently designed, vertical-axis, Small Price current meter (on 

which only a single rotor is required) is the favored instrument of the Survey, but for several of its earliest 

years, meters of the type just described had been 

preferred. 

Other European Developments 

Moore's Current Meter 

While the foregoing events were taking place in 

the United States, European engineers were also taking considerable interest in the design of current me-
68 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 70.—A current meter patented in 1875 in the United States by Benjamin T. Moore of 

Middlesex County, England (NMHT 308551, Smithsonian photo 44536-H.) 

ters. The Saxton and Revy meters manufactured by 

Elliott Bros, in London, and the Baumgarten meters 

manufactured by Lerebours and Secretan in Paris, 

have already been discussed, but no mention has yet 

been made of the Moore or Ott meters made respectively in England and Germany. 

Benjamin T. Moore obtained a U.S. Patent (No. 

169024, dated 19 October 1875) for his "current meters, water meters, and ships' logs." On 1 January 

1876, he used the current meter to measure the flow 

of the Thames River at Staines, about 20 miles upstream from London. (The discharge amounted to 

2612 cubic feet per second.) 

At the time this patent was granted to Moore, current meters were all classified by the U.S. Patent Office under "Ships' Logs." 

The earliest American patents for current meters were taken 

out in 1851. There are now [1927] on file in the Patent 

Office, classified under ships' logs, more than 50 patents for 

devices for measuring the velocity of water. Many unpatented devices have also been constructed.8

' 

Moore not only described his instruments in his patent, but he also submitted to the Patent Office a 

model of his current meter. That model was later transferred to the Smithsonian Institution (Figure 70). 

The Firm of A. Ott 

In 1790, Reinhard Woltman publicly introduced his 

horizontal-axis water current meter. Its basic design 

soon became traditional and many of the improved 

models which came after it were called "Woltman" 

meters, out of respect for the original inventor. A firm 

that perhaps has done the most to preserve this tradition is that of A. Ott of Kempten, Bavaria—today in 

West Germany. Albert Ott (1847-1895), its founder 

(Figure 71a), was the son of a farmer and postmaster 

in Nesselwang, South Bavaria. After serving an exacting apprenticeship in the shop of his uncle, Clemens 

Riefler, who manufactured drawing instruments in 

Nesselwang, he attended the Polytechnic School in 

Munich. For short periods thereafter, he worked at 

instrument shops in Munich, Vienna, Berlin, London, 

and Milan before returning to Bavaria. 

In 1873, A Ott and G. Coradi became partners in 

a small shop in Kempten, where they manufactured 

surveying instruments. Seven years later, however, Coradi left for Zurich to establish a separate, and subsequently famous, shop of his own. 
NUMBER 28 69 

FIGURE 71.—The Ott family of instrument manufacturers: a, Albert Ott, 

founder of the firm of A. Ott; b, Herman Ott; c, Ludwig A. Ott. 

Upon being left the sole owner of the shop in 

Kempten, Ott sought ways of increasing his line of 

scientific instruments. In 1881, therefore, when a leading hydraulic engineer, Professor Andreas Rudolph 

Harlacher, head of the Hydrographic Services 

in Bohemia, proposed to Ott that he manufacture 

Woltman current meters supplied with electric registering facilities on which Harlacher possessed a patent, Ott complied eagerly. Ever since then, the Ott 

firm has supplied Germany and many other countries 

throughout the world with current meters, practically 

all of which have been of a horizontal-axis type such 

as Woltman had originally conceived. 

This was a family-owned firm, and when Albert 

died, it was inherited by his two sons, Herman (Figure 

716) and Ludwig (Figure 71c) with Ludwig (when 

coming of age) taking the most active part in its operations. In the course of time, Ludwig received a Doctor of Engineering degree from the Technical 

University in Munich, and was honored for the excellence of his hydrometric, cartographic, and mathematic instruments. Among the several instruments 

manufactured by the Ott firm that have been contributed to the Smithsonian Institution are the two 

fairly recent current meters shown in Figure 72. 

After Ludwig Ott's death in 1946, his elder brother, 

Herman, carried on the administrative and developmental work. 

Steponas Kolupaila 

During the course of its highly successful operations, 

members of the Ott firm collaborated with many distinguished European hydraulic engineers and often 

incorporated their suggestions into their instruments. 

The circumstances under which one such engineer, 

Dr. Steponas Kolupaila (1892-1964) became involved 

warrants special attention here. 

Before World War II, Kolupaila had been in charge 

of Lithuania's Hydrometric Bureau, an agency which 

was comparable to that of the Water Resources Division of the U.S. Geological Survey. Data concerning 

the discharge of rivers in Lithuania were collected 

and published under his supervision, as was the rating 

and repair of the current meters used on such work. 

In fact, the meters used in neighboring countries like 

Estonia and Latvia were often sent to him to be rated. 

In 1940, Estonia, Latvia, and Lithuania were overrun by the Russian army, and their freedoms as independent republics came to an end. Dr. Kolupaila was 

among the few scientifically trained engineers who 
70 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

n—^— 

a 

FIGURE 72.—Ott current meters: a, ca. 1917 (NMHT316593, Smithsonian photo 72242); 

b, ca. 1932 (NMHT 316595, Smithsonian photo 72256). 

fled to Germany, where he found employment in the 

firm of A. Ott. One of his projects during the four 

years while he was there was to develop a rotor for 

use on horizontal-axis meters that would register only 

that component of the velocity of a stream which corresponded with the direction in which the meter was 

pointing. In other words, if a meter held on a rod, 

were pointed directly into the current, the rotor would 

register 100 percent of the velocity in effect there, 

whereas if it were pointed at right angles from that 

direction, the rotor would not turn at all. At any 

intermediate angle, the rotor would revolve at a rate 

which represented the corresponding component of 

the velocity. This innovation is of particular importance where a meter can be held in a fixed position 

and used in highly turbulent water, or in places where 

water tends to flow at unpredictable angles such as 

occurs in the vicinity of hydraulic turbines. 

Kolupaila succeeded in developing such a rotor. Before leaving that firm in about 1944 to accept a position in America as Professor of Civil Engineering at 

the University of Notre Dame, the Ott firm presented 

him with one each of the major instruments on which 

he had contributed improvements. The instrument 

case containing a current meter with his "component" 

rotor, carries a brass plate engraved as follows: 

TO OUR HYDROMETRICAL COLLABORATOR 

PROFESSOR STEPONAS KOLUPAILA 

IN GRATITUDE FOR VALUABLE SCIENTIFIC WORK 

A. OTT, MATH. MECH. INSTITUTE 

KEMPTEN, BAVARIA 

After Kolupaila's death in 1964, that case of current meters, which included numerous accessories, was 

presented to the Smithsonian Institution (Figure 73). 

His "component rotor" appears in Figure 74. 
NUMBER 28 71 

P pi 

£ 

FIGURE 73.—Current meters and accessories presented to Dr. Steponas Kolupaila for designing 

the "component rotor." (NMHT 328631, Smithsonian photo 62664.) 

FIGURE 74.—A modern Ott meter equipped with Kolupaila's 

"component rotor." (NMHT 328631, photo by A. H. Frazier. ) 
72 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

VERTICAL-AXIS METERS 

During the development of instruments for stream 

gaging, a number of current meters were produced, 

which, although never generally accepted, are nevertheless of considerable historical interest. Such was the 

case with the Hooke and Focacci meters, previously 

discussed, and such was the case with the little-known 

Tolotti meter. 

Most of the presently available information concerning the Tolotti meter is contained in a little 

pamphlet entitled Rota Indrometra, by Antonio Sempiterni Tolotti. The drawings in that pamphlet were 

obviously prepared by an unskilled draftsman, so a 

more readily understood modern perspective drawing 

thereof is being presented in Figure 75. The apparatus 

consisted of a circular rotor with seven equally spaced, 

V-shaped vanes around its periphery, all mounted 

within a box-like container. The downstream face of 

that container was left completely open, but a half of 

its upstream face was closed to form a shield for the 

vanes moving in the upstream direction (a practice 

followed in several modern instruments). Its axle was 

supported on an upward-pointing pivot (also a modern practice). The axle projected well above the surface of the water, where a pointer was attached to it, 

which enabled the operator to count and time its 

revolutions. Although this apparatus badly lacked 

streamlining, the principle of its operation is essentially the same as that of many modern current meters. 

The Tolotti current meter in turn had forerunners 

FIGURE 75.—Tolotti's "rota idrometrica," ca. 1823, a forerunner of modern vertical-axis current meters. (Drawn by 

A. H. Frazier, from Tolotti, Rota Idrometrica.) 

FIGURE 76.—Cross-section of early Persian windmill, a forerunner of the Tolotti current meter. (Drawn by A. H. Frazier after Vowles, "Early Evolution of Power Engineering," 

plate 24.) 
NUMBER 28 73 

of its own but in the meteorological field. For example, in an article entitled "Early Evolution of Power 

Engineering" by Hugh P. Vowles is a "diagrametric 

cross-section of a Persian windmill," a copy of which 

appears in Figure 76. The windmill too, operated on 

the same principle, and Vowles implied in his article that such windmills may have been used in Persia 

as early as the 7th century A.D. 

FIGURE 77.—Daniel Farrand Henry. Note parts of a current 

meter and counting mechanism on table; cf. Figure 78. 

(Painting by Percy Ives, courtesy of Prismatic Club, Detroit, 

Michigan.) 

The Henry Meter 

The current meter that initiated the present vogue 

of current meters of the vertical-axis type was the one 

designed by Daniel Farrand Henry (1833-1907) of 

the U.S. Lake Survey in 1868 (Figure 77). A replica 

of the meter is now in the Smithsonian collection 

(Figure 78). 

Not long after the Civil War, Henry (no relation 

of Joseph Henry, the first Secretary of the Smithsonian Institution) had received orders from his supervisor, General William Franklin Raynolds, to measure 

the discharge from several of the Great Lakes. During 

the course of that project, he built a current meter 

like that shown by installing a flier (rotor) from one 

of his Robinson cup-type anemometers into a suitable 

frame and fitting it with an electric contact facility 

for counting its revolutions (the first successful device 

of that nature). He rated the assembly in the still 

waters of a convenient reservoir. The complete story 

regarding this historic meter appears in the Fall 1964 

issue of Technology and Culture.66 

Despite the fact that both Henry and his supervisor 

were severely disciplined by the Chief of Engineers, 

General A. A. Humphreys, for not having followed 

the "double float" method prescribed in the famous 

Humphreys and Abbot report on the Mississippi RivFIGURE 78.—Replica of Henry's cup-type, electric-contact current meter. 

(NMHT 317670, Smithsonian photo 72258.) 
74 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

er, this meter started the vogue favoring vertical-axis 

cup-type current meters, which persists throughout 

North America to this very day. 

When, in 1876, the United States International Exhibition was held in Philadelphia for commemorating 

the Nation's first centennial, Henry was persuaded to 

exhibit his current meter and an inlet pipe strainer 

for water works as a part of the display of the American Society of Civil Engineers (an organization of 

which he was a member). Because of the electrical 

counting facility he had installed on that meter, it 

became classified among the "electric" rather than 

the "hydraulic" instruments at the exhibit. Joseph 

Henry of the Smithsonian Institution judged those instruments, and it was he, therefore, who wrote the 

following Judge's report awarding Henry a medal for 

his exhibits: 

AWARD 351: D. FARRAND HENRY, DETROIT, MICHIGAN, U.S.A. CURRENT METER AND INLET PIPE 

' AND STRAINER FOR WATER WORKS 

Report 

Commended for an improvement on the ordinary form of 

current meters and for the application of electricity to the 

recording part of the instrument; also for the arrangement 

of a strainer and inlet pipe for water works, so as to prevent 

the interruption from the accumulation of anchor ice. 

The Ellis Meters 

The man who had pursuadcd D. F. Henry to exhibit his current meter at the Philadelphia exhibition, 

was General Theodore Grenville Ellis (1829-1883) 

(Figure 79), a vice-president of the American Society 

of Civil Engineers, and the Chairman of its Centennial Commission. During the Civil War, he had participated in the Battle of Antietam and no less than 

23 other engagements while pursuing General Lee to 

Appomattox. After the war he returned to Hartford, 

Connecticut, where he had made his home since 1854, 

and resumed his engineering activities. In 1867 he was 

placed in charge of the U.S. Corps of Engineers' navigation-improvement study of the Connecticut River, 

a job on which he remained for about ten years. 

While measuring the flow of the Connecticut during his earlier years on that job, he initially followed 

the procedure recommended in the Humphreys and 

Abbot report, namely that of using the double-float 

method. Like Daniel Farrand Henry in the Great 

Lakes area, however, he ultimately decided to give 

FIGURE 79.—General Theodore G. Ellis. 

(Courtesy of Library of Congress.) 

current meters a trial. One of his first steps in that 

direction was, as previously stated, to acquire the 

Baumgarten meter which Clemens Herschel had purchased from the Secretan firm in Paris (Figure 57). 

In the meantime, Henry, with the consent of his 

supervisor, General Raynolds, had been using his cuptype current meter with gratifying success. Reports 

thereon were being printed in the same House and 

Senate Executive Documents in which the reports of 

Ellis' own work on the Connecticut River were being 

published, so he became fully aware of them as well 

as aware of the criticism which the Chief of Engineers 

Humphreys was heaping upon those two hapless Lake 

Survey engineers. Despite that criticism, Ellis proceeded in 1874 to build a current meter very similar 

to, but much smaller than, Henry's. His official report 

thereon, supported by his own immediate superior, 

General G. K. Warren, was expressed in such diplomatic language that Humphreys even praised his action. By the time the Ellis' report of 20 March 1875 
NUMBER 28 75 

was being prepared, the controversy in the Corps of 

Engineers about the use of current meters had subdued to such an extent that Ellis ventured to add the 

following footnote to his description of the new current meter: 

A telegraphic current-meter was first used by D. Farrand 

Henry, esq., civil engineer, upon the United States lake survey, and to whom the writer is much indebted for valuable 

suggestions in the use of the instrument. A full description of 

Mr. Henry's meter will be found in the Journal of the Franklin Institute, volume LXI.00 

Figure 80 shows the two earliest versions of his 

meter, both of which are in the Smithsonian collection. 

They differ from each other in that the more recent 

model (Figure 806) is provided with a "contact 

chamber" which houses both the upper bearing of the 

rotor as well as the electric contact facility. In the 

earlier model (Figure 80a), the contacts took place 

in the open water, the method diat had been used on 

the Henry meters. It may be noted that the original 

model corresponds exactly with the illustration in Buff 

and Berger's 1885 catalog, as previously shown in Figure 63. 

The use of Ellis meters spread quite rapidly after 

he had rated his first model in June 1874, particularly 

among the hydrographers of the Corps of Engineers 

(then the largest group of current meter users in die 

United States). With the introduction of the meter 

designed by W. G. Price in 1882, however, its popularity soon came to an end (page 78). 

The Nettleton Meter 

Edwin S. Nettleton (1831-1901) (Figure 81), was 

born in Medina, Ohio, and educated at the Medina 

Academy and Oberlin College, after which he became 

an apprentice of Zacharia Deane in civil and mechanical engineering. He reached the age of maturity when 

Horace Greeley's admonition, "Go West, young man, 

FIGURE 80.—Early Ellis current meters: a, as originally designed (NMHT 317669, Smithsonian photo 72257) i b, with first improvement (NMHT 289637, Smithsonian photo 44538). 
76 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

^ M IjfeMtJ ^^^1 

FIGURE 81.—Edwin S. Nettleton and his current meter. 

(Portrait from Eleventh Biennial Report of the State Engineer to the Governor of Colorado for the Years 1901 & 

1902; meter NMHT 289641, Smithsonian photo 44537-H.) 

and grow up with the country," began to have its 

greatest effect.91 

Apparently inspired by Greeley's oratory, Nettleton 

joined the Union Colony emigrating to Colorado in 

1870 as its engincer-in-chief. Upon their arrival in 

that State, he laid out the town and surroundings of 

Greeley, and built its irrigation canals. In 1871 he 

laid out the towns of Colorado Springs and Manitou, 

complete with a canal system for that area. 

By 1881 the legislature of Colorado had appointed 

its first State Engineer, one Eugene K. Stimson, who 

served in that capacity for the fiscal years of 1881 and 

1882. He was followed by Edwin S. Nettleton, who 
NUMBER 28 77 

carried that work forward for the next four years. It 

is of interest in this connection that during most of 

those years his Assistant was Ellwood Mead, for 

whom Lake Mead, the lake impounded by the wellknown Hoover Dam between Arizona and Nevada, 

has been named. 

Of greater interest, insofar as the present study is 

concerned, is the current meter that Nettleton designed. In his account of the stream-gaging operations 

published in the Biennual Report to the Governor of 

Colorado for 1883-1884, he remarked: 

At first the Fteley current meter was used for measuring current velocity, but it was soon apparent that this instrument 

was entirely too delicate for the rough torrents, filled with 

drift of all sorts, in which it was necessary to use it. An instrument was designed by me more suitable to the work 

(named the "Colorado" current meter), a description of 

which is given elsewhere. The main object kept in view in 

designing this instrument, was to make it self-clearing, the 

great defect of the Fteley meter being its liability to error 

from clogging with grass, weeds, etc. which at times would 

vitiate many hours' work Three "Colorado" meters 

having been made for this department by W. E. Scott & Co. 

of Denver; these instruments have since been in continuous 

FIGURE 82.—The "Bailey" meter, a modified version of Nettleton's meter, ca. 1889. 

(NMHT 24896, Smithsonian photo 44538-A.) 
78 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

use in gauging rivers and ditches giving entire satisfaction. 

I Italics added.] 

One of the current meters built for him by W. E. 

Scott & Co. is shown in Figure 81. It will be seen that 

the major change from the Fteley-Stearns current 

meter (Figure 61) consisted of substituting a verticalaxis rotor, such as General Ellis had used on his meters, for the horizontal-axis, screw-type rotor that 

Fteley preferred. 

In 1889, after the U.S. Geological Survey's "Camp 

of Instruction" for the Irrigation Survey got under 

way at Embudo, New Mexico, Nettleton, like California's State Engineer William Hammond Hall, lent a 

model of his current meter to that Survey. Soon the 

engineers at that camp redesigned Nettleton's meter, 

just as they had redesigned the Navy Department's 

Haskell meter, only this time the change was not as 

drastic. It consisted merely of enclosing the counting 

wheels within a glass-covered compartment so as to 

keep silt and the plant fibers from interfering with the 

action of the gears. The revised instrument became 

known as the "Bailey" meter (Figure 82), presumably 

because most of the change had been accomplished by 

the junior member of the firm in Denver then known 

as "Lallie and Bailey." As in the case of the Nettleton 

meter discussed above, one of these original "Bailey" 

meters, after having been preserved for many years by 

the Geological Survey, was transferred to the Smithsonian Institution. 

The Price Meters 

All of the remaining current meters presently in the 

Smithsonian collection are vertical-axis, "Price-type" 

models having cup-type rotors. As in the case of the 

previously described Woltman meters, numerous modifications have been made from the original model 

built by Price, but his name has always remained attached to all of them even though some have failed to 

meet his approval. Meters of this type are by far the 

most commonly used in North America, whereas those 

of the horizontal-axis type are the most popular in 

Europe. 

William Gunn Price (1853-1928) (Figure 83) was 

born in Knoxville, Pennsylvania, but spent most of 

his youth in Chaseville, New York, about two miles 

southwest of the picturesque village of Schenevus. His 

aptitude for invention and engineering became evident quite early, and after having received four years 

FIGURE 83.—William Gunn Price. 

(Courtesy of W. G. Price, Jr.) 

of instruction in mathematics and engineering under 

J. H. Serviss at Engle wood, New Jersey, he embarked 

on a brilliant career in both of those fields.93 

Between 1879 and 1896 Price was an assistant Engineer with the Mississippi River Commission, measuring the flows of the Mississippi, Ohio, and Missouri 

rivers, including many of their tributaries. In 1882, 

after having installed a river gage on the Ohio River 

at Paducah, Kentucky (Figure 84), he conceived the 

design of his first current meter. The circumstances 

which prevailed on that occasion are described in the 

following letter which he wrote on 20 April 1927 to 

Nathan C. Grover, then Chief Hydraulic Engineer of 

the United States Geological Survey: 

In January, 1882, I began measuring the discharge of the 

Ohio at Paducah, Kentucky, under orders of Captain Smith 

S. Leach, Corps of Engineers, U.S.A., who was Secretary of 

the Mississippi River Commission. My equipment included a 

meter which was designed by Clemens Herschel. 

The Herschel meter was of the propeller type, having a 

horizontal shaft, and there were no means for excluding 

water from its bearings. 
NUMBER 28 79 

FIGURE 84.—The catamaran used by W. G. Price in 1882 for measuring the flow of the Ohio 

River at Paducah, Kentucky. Note current meter next to Price, second from right at stern of 

boat. (Courtesy of W. G. Price, Jr.) 

The Ellis meter had a cupped wheel which revolved in a 

horizontal plane, and there was no provision for excluding 

water from its vertical-shaft bearings. 

I rated these meters in clear, still water, and plotted 

ratings indicated that they would give accurate measurements. 

I then began using them for river measurements. The 

water was very muddy, and boils in the swift current carried 

fine sand to the surface which I caught in my drinking cup. 

Neither would give discharge measurements which corresponded with the gradual increase in gage. 

I then rated both meters in a bayou which had been 

recently filled with muddy water from the river, and the 

rating dots were irregular in location. Some dots indicated 

an increase of friction in the wheel bearings. 

I then rated the meters in a smooth-flowing chute, carrying sand and fine silt from the river. The meters were 

moved alternatively upstream and downstream. These ratings 

were very innaccurate, indicating the effect of grit in the 

bearings. 

I then wrote to Captain Leach that using these waters, I 

was unable to secure discharge measurements which at all 

corresponded with the daily increase in stage. The river was 

having a slow continuous rise. I asked Captain Leach to 

send me a meter which would give accurate measurements. 

The next day at 5 p.m. I received the following telegram: 

"Have no meter to send you. Do the best you can." 

Almost immediately the idea occurred to me that by using 

inverted cup bearings which would trap air, I could exclude 

the water and grit. I made drawings for such a meter that 

night, and by employing four mechanics, the meter was completed the next day at 3 p.m. 

This meter was used for measuring the great flood of that 

year, 1882.91 

In other documents, Price explained that among 

those mechanics he had employed to build the meter 

was a tinsmith, a blacksmith, and a locksmith. They 

were the best mechanics in town. The actual current 

meter constructed on that occasion is now one of the 

most treasured current meters in the Smithsonian collection (Figure 85). 

Among the many U.S. patents that have been 

awarded to Price, the following four were for current 

meters: No. 325,011 dated 25 August 1885; No. 
80 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 85.—The original Price current meter, built by him and four mechanics at Paducah 

Kentucky, in 1882. (NMHT 289638, Smithsonian photo 44538-H.) 

O I lull H FH IJ" 'I r"i ifi ~

r 

FIGURE 86.—Price's current meters, ca. 1886, manufactured by W. & L. E. Gurley: a, 34-inchlong %'ersion (NMHT 311708, Smithsonian photo 44538-D); b, 24-inch-long version' (NMHT 

289642, Smithsonian photo 44538-G). 
NUMBER 28 81 

FIGURE 87.—W. G. Price's subsurface direction meter with cover in place ca. 1886. 

(NMHT 316592, Smithsonian photo 72239.) 

582,874 dated 18 May 1897; No. 1,413,355 dated 18 

April 1922; and No. 1,571,433 dated 2 February 1926. 

On 14 January 1885, just before Price applied for 

the first of those patents, he wrote to the W. & L. E. 

Gurley firm of Troy, New York, saying in part: 

It is a great trouble to me to find a machinist who can make 

them, and I have been obliged to do all of the fine work 

myself. I wish you would undertake the manufacture of these 

instruments and furnish them to the U.S. Government at a 

reasonable price. .. . Of course, there is not much demand 

for them just now, as engineers are only just finding out that 

it is the only accurate way to measure the discharge of rivers. But the engineers on the Mississippi alone are likely to 

require as many as 3 or 4 every year . . . .

95 

Before the end of that year (1885), Price entered into 

a contract with the Gurley firm to manufacture his 

current meters on a royalty basis, and took a model of 

his 32-inch-long meter to them as a sample. While in 

Troy, a decision was reached for Gurley to manufacture not only one, but two different models. The larger thereof (34 inches long, with a 7'/2-inch-diameter 

rotor) was announced in the 26th edition of Gurley's 

Manual of the Principle Instruments Used in American Engineering and Surveying (January, 1886) as 

their Item No. 375, "Deep Water and Harbor Meter," 

and the smaller (24 inches long with a 6-inch-diameter rotor) as their Item No. 376, "River and Smaller 

Stream Meter." At the same time they introduced a 

Subsurface direction meter of Price's design which 

registered the compass direction of the velocity in the 

location at which it was positioned in the water. 

Models of these three instruments are shown in 

Figures 86 to 88. The 34-inch-long model (Figure 

86a) had originally been purchased from Gurley's by 

the Mississippi River Commission in about 1890. It 

was used until 1929 by their engineers for measuring 

the flow of the Mississippi at various points between 

Rosedale and Vicksburg, Mississippi, and finally transFIGURE 88.—Price's subsurface direction meter assembly with 

compass cover removed. When observations are made, an 

electrical current operates a solonoid within the sphere, 

which locks the position of the compass both vertically and 

horizontally until a reading is taken. (Courtesy of W. & 

L. E. Gurley.) 
82 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

ferred to the Smithsonian in 1939. The shorter model 

(Figure 866) had been owned and used for many 

years by the U.S. Geological Survey before being 

transferred to the Smithsonian in 1916. 

Price was probably the Nation's foremost authority 

on current meters for a longer period than anyone 

else either before or after his time. Beginning in 1883, 

just one year after he had invented his first model— 

and continuing for ten years thereafter—he was in 

charge of the discharge-measuring operations of the 

Mississippi River Commission. He conducted many 

hydraulic studies such as those concerned with the 

shape of the vertical-velocity curves in rivers, and 

with the relationship between the velocity of the water 

at mid-depth as compared with the average velocity 

in the entire vertical at the same location. His active 

interest in such subjects continued until the very last 

days of his life. 

On one occasion in 1894, while working on the 

Missouri River for the Mississippi River Commission, 

he delivered a speech on irrigation at a conference at 

O'Niell, Nebraska. Newspaper accounts of that conference described him as an "enthusiastic irrigationist." In response to a need he found in that field, he designed and patented his "Acoustic Current Meter" 

(Figure 89). Tha t meter received its earliest publicity 

in an article entitled "A New Current Meter, and a 

New Method of Rating Current Meters" in the 10 

January 1895 issue of Engineering News. It too, was 

manufactured by W. & L. E. Gurley. 

The rotor on this meter is smaller (only 5 inches 

in diameter) and lighter than that on any previous 

model. The word "acoustic" was used to identify it 

because of the manner in which sound was conducted 

from the instrument up to the ear of the operator. 

While the rotor would be making ten revolutions in 

the water, a worm gear on the upper end of its axle 

(which extended to the top of the enlarged chamber 

on the rod) would cause a lever (in the form of a 

tiny hammer) to be depressed against a spring. Upon 

completion of each tenth revolution, the hammer 

would be released, causing it to swing upwards and 

strike a metal diaphragm located in the upper end of 

the chamber. This cycle of operations would then be 

repeated over and over again as long as the rotor continued to turn. The sound produced each time the 

FIGURE 89.—Price's "acoustic current meter," ca. 1895, without brass suspension rods. 

(NMHT 316594, Smithsonian photo 72243.) 
NUMBER 28 83 

hammer struck the diaphragm would proceed up the 

inside of the hollow suspension rods to the earpiece 

worn by the operator, thus enabling him to count, by 

tens, and to time a certain number of the revolutions 

with a stopwatch. With the information thus obtained, 

he could enter a table of corresponding velocity values, 

and convert it into a figure representing the velocity 

of the water at the point of observation. These acoustic current meters were quite popular in North America for many years after their introduction. 

The last two current-meter patents awarded to 

Price were never manufactured. They both reflected 

an opposition he felt toward some of the changes that 

were being made from his earlier designs, and he had 

hoped to correct them. About two years after having 

received his final patent, he left on a trip from his 

home in Yakima, Washington, to Troy, New York, 

to confer with members of the W. & L. E. Gurley 

firm about manufacturing new meters which would 

contain those latest improvements; but that plan was 

never consummated. He got only as far east as Detroit, 

Michigan, when he was seized with a heart attack 

and taken off the train. Fie died soon thereafter in 

Detroit's Fort Shelby Hotel on 6 July 1928, his 75th 

birthday. 

The Geological Survey in the U.S. Department of 

the Interior became particularly concerned with current meters and stream-gaging methods on two separate occasions. The first was for a short period from 

1888 to 1890 when, as previously noted, the U.S. 

Irrigation Survey became a part of its activities. The 

second had its beginning in 1894, when Congress 

started appropriating funds for what is now known 

as the Water Resources Division of the Geological 

Survey. 

Before 1895, horizontal-axis current meters, such 

as those of the Haskell type which had been modified 

by engineers of the Irrigation Survey (Figures 68 and 

69), had enjoyed the greatest popularity. In March 

of that year, however, the University of Nebraska, 

which owned one of the smaller-sized Price current 

meters (Gurley's model No. 376 [Figure 866]), lent 

it to Professor O. V. P. Stout, a per diem employee of 

the Geological Survey, for making a streamflow measurement. His report to the Survey about its performance was so enthusiastic, that within two months, the 

Geological Survey acquired one of its own. Tha t 

occasion marked the beginning of the Survey's preference for meters of the Price type, a preference that is 

still in vogue. The Geological Survey has perhaps 

owned more current meters than any other organization in the world. Well over 95 percent of them have 

been of the Price type. 

The early hydrographers in the Water Resources 

Division of the Geological Survey soon found it necessary to accommodate themselves to a great variety 

of measuring conditions while gathering its streamflow 

data. Streams ranging in discharge from a mere trickle 

to the flow of the mighty Mississippi fell under their 

purview. Measurements varied in character from 

those made while wading the smaller streams to those 

made from bridges, cableways, boats, and even from 

ice cover. The instrumentation problems connected 

therewith were invariably the subject of many discussions at the annual conferences of the Survey's district 

engineers. Prior to the conference held in Washington, 

D.C, in 1896, the Chief of the Division, Frederick 

Haynes Newell (1862-1932), requested that those engineers come prepared to submit suggestions for improving the current meters then in use. Edwin Geary 

Paul (Figure 90a,b), the mechanician of the Division, 

was instructed to incorporate the most practical 

thereof in the design of a new meter. His design, and 

its construction by W. & L. E. Gurley was completed 

on 12 November 1896 (Figure 90c) ; Paul, assisted by 

C. C. Babb of the Survey, rated it on 10 December 

of the same year at the rating station at Chevy Chase 

Lake, Maryland. This 12-inch-long meter, presently 

in the Smithsonian's collection made use of the same 

5-inch-diameter rotor that had been used on the Price 

acoustic meters. Its other parts were quite similar to, 

but considerably lighter than those on the large 

earlier models, which Gurley had been manufacturing. 

Because of its unusual method of suspension, there 

was no necessity for providing a horizontal vane on 

its tailpiece. It did, however, retain the electric contact facility which characterized all cup-type current 

meters (other than the Price acoustic models) since 

the time of Daniel Farand Henry. 

This experimental model is the first Small Price 

current meter to have been built. Its lightness, and the 

ability to disassemble and pack it in a very small space 

appealed to many of the field hydrographers who 

often had to carry them and several other items of 

equipment for long distances on foot. It had been 

designed for cable suspension only, however, a circumstance that made it necessary for the field men 

to be supplied with a second meter that was capable 

of being suspended on a rod. Consequently, the design 

was soon modified to provide for both rod and cable 
84 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 90.—Edwin Geary Paul and his Small Price current meter, 1896: a, E. G. Paul, ca. 1900; 

b, Paul, seated behind the U.S.G.S. rating car at Chevy Chase Lake, Maryland, ca. 1896; c, original experimental model, built by W. & L. E. Gurley, Troy? New York, (a, Courtesy of Mrs. 

E. G. Paul; b, from U.S.G.S. Water-Supply and Irrigation Paper, 56, plate 12A; c, NMHT 

289643, Smithsonian photo 44538-E.) 

suspension. The resulting model appears in Figure 

91. (The accessory called a "double-end hanger," 

which could be installed between the tailpiece and 

the yoke for accommodating a suspension rod, is not 

shown in the photograph.) This model met with general approval among the Geological Survey's field 

engineers, and the Gurley firm began manufacturing 

them as a stock item. That firm continued to be the 

primary manufacturer of such meters until several 

years after the Price patents had expired. 

Because of the many river-gaging stations that the 

Geological Survey established, its needs for current 

meters inevitably kept increasing. A point was finally 

reached where, to assure a continuing supply of repair 

parts, it needed to write its own specifications for 

these instruments. At about the same time, the Survey 

developed a policy of designing each new innovation 

in such a way that it could be incorporated in all of 

their earlier meters by merely replacing an old part 

with the appropriate modern one, thus up-dating the 

old models, and saving the expense of purchasing 

entirely new replacement meters. 

The two remaining current meters in the Smithsonian collection, (Figures 92 and 93) reflect that pol-
NUMBER 28 85 

icy. By about 1908, the meter's yoke was changed to 

provide a slot through which a thin, flat "hanger5' 

could be passed for suspending the meter and to take 

the place of the bulky "hanger" shown below the on the model shown in Figure 93, although the most 

meter in Figure 91. The new hangers were less expensive, less bulky, and far more streamlined than 

those earlier models. The improved yoke can be seen 

FIGURE 91.—One of the earliest Small Price current meters to be commercially manufactured, 

ca. 1897, by W. & L. E. Gurley. (NMHT 289644, Smithsonian photo 44538-F.) 

FIGURE 92.—An experimental Small Price current meter, ca. 1908; the first to be furnished 

with a "penta" contact chamber. (NMHT 289645, Smithsonian photo 44538-B.) 
86 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 93.—A commercial Small Price current meter with Covert yoke and with one of its 

two interchangeable contact chambers, ca. 1912. (NMHT 323836, Smithsonian photo 44537-D.) 

important feature of that particular meter is the new 

"penta count" contact chamber on it. On all earlier 

models of Small Price current meters, the contact 

facility within such chambers was so designed as to 

produce just a single electrical contact for every revolution of the rotor. During the period 1906 to 1908, 

however, John C. Hoyt of the Survey proposed that 

meters be supplied with an extra contact chamber 

within which a single contact would be made at each 

fifth revolution thereof. The idea of a worm-and-gear 

arrangement was borrowed from the acoustic meters 

for this purpose. 

The meter shown in Figure 93 is the very model 

which contained the first experimental "penta" contact chamber. Because velocities measured during 

flood periods would often cause the rotors to revolve 

too rapidly for the operator to count the revolutions 

accurately, and because Floyt's idea could overcome 

that difficulty in a very satisfactory manner, it was 

quickly adopted. Another innovation, proposed in 

1912 by C. C. Covert, a district engineer of the Geological Survey frcm New York State, consisted of casting a "boss" on the upper limb of the yoke into which 

a wading rod might be screwed. Streams in that State, 

as in all other northern States, are prone to freeze 

over during the winter months, and before hydrographers could measure them, they had to chop a large 

number (usually 20 or more) holes through the ice. 

By suspending the meters in this new manner, the tailpiece of the meter could be removed, and the size of 

the holes, together with much of the arduous labor, 

could be considerably reduced. Tha t idea also met 

with approval, and the current meter shown in Figure 93 reflects Covert's innovation as well as the commercial version of Hoyt's idea concerning the "penta" 

contact chambers. The meter shown in this figure is 

the last of the Small Price meters presently in the 

Smithsonian collection, a collection which reflects 

practically all of the improvements in the verticalaxis, cup-type models from their first conception up 

to those made in 1925. Since then, only a few minor 

innovations have been added. The pivots on which 

their rotors have revolved, for example, have since 

had their lengths changed three times, with the longest of the lot being the present favorite. The only 

other change consisted of incorporating both the 

"single contact" and "penta contact" features within 

a single contact chamber having two electrical binding 

posts. Since that idea was adopted, hydrographers 

have needed only to connect the lead wire to whichever terminal best suited their needs. A modern Small 

Price meter, provided with all of those latest innovations appears in Figure 94. 

When undertaking a study of current meters such 

as this, one cannot help being impressed with the 

persistence with which each new design tenaciously 

hangs on throughout the years. Rod floats such as 

introduced by Leonardo da Vinci, for example, are 
NUMBER 28 87 

FIGURE 94.—A Small Price current meter of the type now in use. 

(Property of the U.S. Geological Survey; photo by A. H. Frazier.) 

still being used under certain special conditions, and 

the same circumstances prevail with respect to practically all of the other instruments discussed here. 

In this connection, it should be explained that no 

attempt has been made to discuss the complete variety 

of devices that are known to have been used for measuring streamflow. During recent years especially, electromagnetic, electronic, acoustic, optical, photographic, radioactive, chemical, and a host of other 

methods have been developed, but none of them have 

yet replaced the conventional, mechanical type of 

water current meters, nor have any of them achieved 

any high degree of popularity. No doubt more than 

95 percent of the streamflow measurements throughout the world are presently being made with mechanical current meters, such as the more modern models 

that have been described here. They are simple in construction, easy to operate, rugged, easy to repair, convenient to transport from one river to another, and 

are relatively inexpensive. It seems unlikely that they 

will become obsolete for many years to come. 

NOTES 

' SINGER, "From Early Times," page 521. 

' FRAZIER, "William Gunn Price." 

3

 BISWAS, History of Hydrology, page 20. 

* NOBLECOURT, "Tutankhamun's Golden Trove," page 632. 

6

 CLICK, "Medieval Irrigation Clocks," pages 424-428. 

* SCIIAACK, "Vergangenheit, Gegenwart," page lOfF. 

' JACOBSEN and LLOYD, Sennacharib's Aqueduct at Jerwan. 

" HERSCHEL, Frontinus and the Water Supply, page 27. 

"Ibid, page 202. 

"COHE N and DRABKIN, A Souue in Greek Science, page 

241. See also Truesdell, "The First Engineer," page 16. 

"FONTANA, Dell' Accrescimento, pages 15-61, as translated by the Engineering Societies Library, New York. 

"Ibid., page [21], as translated by the Engineering Societies Library, New York. 

" SALUSBURY, Mathematical Collections and Translations, 

pages 9-12. 

* GILLISPIE, Dictionary, pages 115-116. 

16

 POGGENDORFF, Geschichte der Physik, page 319. 

16

 SALUSBURY, op. cit. 

"DRAKE , Discoveries and Opinions of Galileo, page 115. 

18

 GILLISPIE, op. cit., pages 115-116. 

" PARSONS, Engineers and Engineering, page 329. 

20

 WOLF, History of Science, page 540. 

21

 GILLISPIE, op. cit. 

a

 SALUSBURY, op. cit. 

" Ibid., page 48. 

24

 Ibid., page 24. 

29

 Ibid., pace 49. 

20

 Ibid., page 6. 

27

 DA VINCI, Manuscript "A" folio 42 V. 

28

 MARINONI, "Tempo Armonico," pages 45-48. 

2B

 MACCURDY, The Notebooks of Leonardo da Vinci, 

page 526. 

m

 MASETTI, "Descrizione, Esamc e Teoria," page 410. 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

31

 HUMPHREYS and ABBOT, Report Upon the Physics and 

Hydraulics," page 225. 

32

 AGRIPPA, Nuove Inventione di Camillo Agrippa. 

83

 ANONYMOUS, "The Life of Monsieur Guglielmini," 

page 177. 

34

 GUGLIELMINI, Opera Omnia, pages 190-195. 

35

 SANTORIO, Commentaria In Primam, pages 345-346. See 

also FRAZIER, "Dr. Santorio's Water Current Meter," pages 

249-253. 

30

 BRUNING, Verhandlingen. 

37

 WOLTMAN, Theorie und Gebrauch, page 3, table 3. 

38

 GRANGER, Vitruvius on Architecture, pages 323-325. 

39

 MILANESE, "Dr. Santorio's Water Current Meter," 

pages 6866-6867. 

40

 MICHELOTTI, Sperimenti Idraulici. 

"ROUS E and INCE, History of Hydraulics, page 130. 

41

 BREWSTER, The Edinburgh Encyclopaedia, pages 

761-762. 

4 3DUBUAT, Principes d'Hydraulique, page 155, as translated by John Macedonia. 

44

 Ibid., page 319. 

48

 BREWSTER, in FERGUSON, Lectures on Select Subjects, 

page 37, plate 1, figure 8. 

46

 MASETTI, op. cit., page 417, as translated by Dr. Carlo 

Zammattio and A. H. Frazier. 

47

 These tests are more fully described in BEARD'S article, 

"Practical Observations on the Power Expended in Driving 

the Machinery of a Cotton Manufactory at Lowell." 

48

 Cf. FRIZELL, "The Water-Power of the Falls of St. Anthony," pages 423-424. 

49

 PITOT, "D'une Machine pour measurer." 

50

 As translated in ROUSE and INCE, History of Hydraulics, 

page 116. 

61

 TROSKOLANSKI, Hydromttry, pages 425-445. 

81

 PARSHALL, "The Improved Venturi Flume," pages 

841-880. 

83

 TAYLOR, The Mathematical Practitioners, page 426. 

84

 USHER, A History of Mechanical Inventions, page 324. 

88

 D E SAUMAREZ, "V. An Account of a New Machine," 

page 411. 

86

 WOLF , op. cit., opposite page 63. 

87

 D E SAUMAREZ, Account of . . . Henry De Saumarez, 

page 4. 

88

 D E SAUMAREZ, "III. A Further Account of a New Machine," "IV. Observations upon the Tides," and "V. An 

Account of a New Machine." 

88

 SAFFORD and HAMILTON, "The American Mixed-flow 

Turbine," page 1241, figures 5 and 6. 

00

 D E SAUMAREZ, "III. A Further Account of a New Machine," "IV. Observations upon the Tides," and "V. An 

Account of a new Machine." 

41

 SMEATON, "LXX. An Account of Some Experiments." 

62

 D E SAUMAREZ, Account of . . . Henry De Saumarez. 

63

 Ibid., page 3. 

04

 SPENCER, "Notes," page 214. 

68

 D E SAUMAREZ, Account of . . . Henry De Saumarez, 

page 8. 

60

 Ibid., page 13. 

67

 Ibid., page 16. 

08

 HOOKE, "A Way-wiser for Sea," pages 84-85. 

09

 FRAZIER, "Joseph Saxton," pages 47-48. 

70

 Saxton diary, Smithsonian Institution Archives, 25 May23 August 1832. 

71

 GREAT BRITAIN, PARLIAMENTARY PAPERS, Report from 

the Select Committee, pages 175-176. 

"HASKOLL , The Practice of Engineering Field Work, 

page 261. 

73

 HUMPHREYS and ABBOT, op. cit., appendix G, pages 

cxxiv-cxxv. 

"Th e appellation of the "U.S. Coast Survey" was 

changed by an act of Congress, 20 June 1878, to the "U.S. 

Coast and Geodetic Survey." See WEBER, Coast and Geodetic Survey. 

78

 PAYSON, "Current-Observations," pages 1304-1318. 

76

 HUMPHREYS and ABBOT, op. cit., page 225. 

77

 FRAZIER, "Daniel Farrand Henry," pages 541-565. 

78

 U.S. ARMY CORPS OF ENGINEERS, Annual Report, 

page 621. 

79

 BAUMGARTEN, "Sur le moulinet de Woltman," pages 

326-357, and VENTUROLI, Elementi di Mechanica e Hydraulica, page 160. 

80

 U.S. HOUSE OF REPRESENTATIVES, "Report of Gen. 

Theodore G. Ellis," pages 304-309. 

81

 Ibid., pages 306-307. 

8 2STEARNS, "On the Current Meter." 

83

 GRUNSKY, "Appendix," page 80. 

84

 Ibid. 

83

 HASKELL, "Reminiscences," page 234. 

86

 FRAZIER, "Embudo, New Mexico." 

87

 HOYT and GROVER, River Discharge, page 7. 

88

 FRAZIER, "Daniel Farrand Henry," pages 541-565. 

89

 HENRY, United States International Exhibition, 1876, 

page 191. 

90

 U.S. HOUS E OF REPRESENTATIVES, "Appendix A," pages 

304-355. 

91

 FRAZIER, "William Gunn Price," page 51. 

92

 NETTLETON, Report of the State Engineer, page 8. 

93

 FRAZIER, "William Gunn Price." 

94

 Files of Chief Hydrologist, U.S. Geological Survey, 

Washington, D.C. 

88

 W. & L.E. Gurley files, Troy, New York. 

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Index 

Abbot current meter, 56, 63 

Abbot, Gen. Henry L., 14, 54, 56, 63 

Academy of Sciences, Paris, 25, 43, 57 

Acoustic current meter, 82 

Adelaide Gallery (London), 52, 53 

Adjutage, 4, 33 

Aggeler, Cecil, 39 

Agrippa, Camillo, 15 

Akhenaten (Pharaoh), 2 

Akron (Ohio) Repository, 51 

Alger, Horatio, 51 

American Philosophical Society, 53 

American Society of Civil Engineers, 74 

Anemometer, 20, 50 

Appomattox, 74 

Aqueducts, 4, 6 

Arizona, State of, 77 

Arno River (Italy), 7 

Austrian Institute of Civil Engineers, 50 

Babb, C C , 83 

Bache, A. D., 53 

Bailey current meter, 78 

Balance scales, 53 

Baldwin, James Fowle, 30 

Baldwin, Loammi, 30 

Barattieri, G. B., 13 

Batchelder, Samuel, 28 

Baumgarten, Andre Gustave Adolphe, 56-59 

Baumgarten current meter, 56-64, 74 

Beard, Ithamar A., 28-31 

Bentzel, Carl E., 35 

Bentzel velocity tube, 35-36 

Berger, C L. & Sons, 61 

Bibliography of Hydrometry, 56 

Bi-filar suspension, 51 

Black Friars, Order of, 7 

Black Sea, 24 

Bligh, Captain William, 45 

Bohemia, 69 

Bologna (Italy), 16 

Bors, 20 

Bosporus, Strait of, 22 

Boston and Lowell Railroad, 30 

Bounty, H.M.S., 45 

Brewster, Sir David, 26 

British Association for the Advancement of Science, 26, 50 

British House of Commons, 41 

British National Maritime Museum, 45 

British Parliament, 41 

Brookline (Mass.), 65 

Brooklyn (N.Y.), 30 

Brunacci, Vincenzio, 13 

Brunings, Christiaan, 21 

Buff and Berger, 62-63, 75 

Buff, George Louis, 61 

Cabeo, Nicola, 13 

California, 63, 

Castelli, Benedetto, 6-8 

Centennial Commission, 74 

Chaseville (N.Y.), 78 

Chevy Chase Lake (Md.) rating station, 83 

Code of Hammurabi, 2 

Codice Atlantico, 9 

Colne River (England), 53 

Colorado Agricultural Experiment Station, 40 

"Colorado" current meter, 77 

Colorado Springs, 76 

Concord River, 28 

Cone, Victor Mann, 40 

Connecticut River, 14, 58, 74 

Conte, 57 

Commissioners of the Admiralty, 47 

Component rotor, 70 

Continuity of flow, 8 

Coradi, G., 68 

Cornell University, 66 

Corps of Engineers, U.S. Army. See U.S. Corps 

of Engineers 

Covert, C C , 86 

Covert yoke, 86 

Croatia, 20 

Cubitt, Joseph, 53 

Cubitt, William, 53 

Cuxhaven (Germany), 50 

Danube River, 24 

Darcy, Henri P.G ., 34 

Dark Ages, 5 

Da Vinci, Leonardo, 8-13, 37, 48 

Deane, Zacharia, 75 

Denver (Colo.), 66, 77-78 

Department of the Interior. See U.S. Department of 

the Interior 

De Saumarez, Henry, 41-47 

Detroit (Mich.), 64, 83 

Direction-indicating facility, 65, 81 

Double floats, 8. See also Floats 

Dubuat, P. L. G , 24-27 

Dummer, John, 28 

Dutch Academy of Sciences, 21 

Ecole des Ponts et Chaussees, 21, 30, 56 

Eddystone lighthouse, 45 

Edinburgh Encyclopaedia, 26 

Egypt, 2 

Elementi di Mechanica e Hydraulica, 56 

Elliott Bros. (London), 50, 53, 68 

Ellis current meter, 74-75, 79 

Ellis, Gen. Theodore C , 14, 58-59 

Embudo (N. Mex.),66, 78 

England, 30, 50, 68 

92 
NUMBER 28 93 

Englewood (N.J.), 78 

English channel, 44-45, 50 

E. S. Ritchie and Sons, 65-67 

Estonia, 69 

Ferguson, James, 27 

Floats, 8-17. See also Double floats, Free floats, Rod floats 

Florence (Italy), 7 

Florida, State of, 65 

Focacci current meter, 36-37, 72 

Focacci, Francesco, 36 

Fontana, Giovan, 6-7 

Fort Collins (Colo.), 40 

Fort Shelby Hotel, 83 

Fossombroni, Vittorio, 36 

Fourcroy, de, 25 

France, 24 

Francis, James, 14, 31, 61-63 

Franklin Institute (Philadelphia, Pa.), 51, 75 

Frederick (Md.), 51 

Free floats, 8-14. See also Floats 

Frontinus, 4, 6-7 

Fteley, Alphonse, 59-61 

Fteley-Stearns current meter, 59-61, 77 

Gaging stations, 1 

Galileo, 6-8, 16 

Garonne River (France), 56, 58 

Gauthey, Edmund Marie, 21 

Geological Survey. See U.S. Geological Survey 

Germany, 68-70 

Ghadames (Oasis), 3 

Golden Gate Park (San Francisco), 63 

Great Exhibition (London), 53 

Great Lakes, 56, 73-74 

Greeley, Horace, 75 

Grover, Nathan C , 78 

Guernsey, Island of, 41 

Guglielmini, Domenico, 15-17, 24 

Gulf Stream, 65 

Gurley, W. & L. E., 81-85 

Hall current meter, 78 

Hall, William Hammond, 63-64, 67, 78 

Halley, Edmund, 46 

Hamilton canal, 28, 31 

Hamilton mills, 28, 29 

Hammurabi, 2 

Harlacher, Andreas R., 69 

Harlacher current meter, 69 

Hartford (Conn.), 74 

Haskell current meter, 78, 83 

Haskell, Eugene E., 64-67, 78 

Haskoll, W. Davis, 53 

Henry current meter, 56, 58, 73-75 

Henry, Daniel Farrand, 56, 58, 73-75, 83 

Henry, Joseph, 74 

Hero of Alexandria, 4-5, 29 

Herschel, Clemens, 37, 58, 61-62, 74, 78 

Herschel current meter, 78 

Hooke current meter, 48-50, 72 

Hoover Dam, 77 

Horizontal-axis meters, 48-71 

House of Commons, 41 

Hoyt, John C , 86 

Humphreys, A. A., 14, 54, 58, 73 

Humphreys and Abbot Report, 73-74 

Hyde Park (London), 45 

Hydroelectric power, 1 

Hydrometry, 16, 36 

Independence Hall, 52 

Integration method, 50-51 

International Boundary and Water Commission, 21 

Irrigation, 1 

Irrigation Survey. See U.S. Irrigation Survey 

Italian Royal Academy of Sciences, 16, 36 

Jerwan (Iraq), 4 

Keeler, Karl Fairbanks, 20-21 

Kempten (Germany), 68 

Knoxville (Pa.), 78 

Kolupaila, Steponas, 56, 69-71 

Lake Mead (Nevada), 77 

Lake Trasimeno (Italy), 7 

Lallie and Bailey, 78 

Lallie, J. S. J., 78 

La Plata estuary, 50 

Large Price current meters, 81-82 

Leach, Captain Smith H., 78-79 

Leonardo da Vinci. See Da Vinci, Leonardo 

Lerebours et Secretan (Paris), 57-58, 68 

Lerebours, Marc, 58, 74 

Leupold and Stevens, Inc., 21, 35 

Lithuania Hydrometric Bureau, 69 

Litigations, 1 

Log line, 47 

Logs. See Ships' logs 

London, 41, 50, 52-53, 68 

Longitude, 41 

Lords Commissioners of the Admiralty, 47 

Louis xiv, 43 

Lowell (Mass.), 14, 28-32, 60-62 

Lowell Courier, 29 

Lukens, Isaiah, 52 

Magazine of Popular Science, 53 

Manitou (Colo.), 76 

Marine surveyors, 41, 45 

Marinoni, Augusto, 8 

Mariotte, Edme, 13, 41 

Marmora, Sea of, 24 

Marsili, Luigi Ferdinando, 22-24 

Martin, John, 53 

Mead, Ellwood, 77 

Merrimack River, 28 

Michelotti, Francesco Domenico, 24 

Milan (Italy), 24, 68 

Milanese, Ferdinando, 24 

Military Academy (U.S.), 30 
94 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Mississippi River, 14, 21, 64-65, 78-81 

Mississippi River Commission, 64-65, 78-82 

Missouri River, 78, 82 

Mitchell, Henry, 65 

Monte Casino Monastery, 7 

Moore, Benjamin Theophilus, 68 

Moore's current meter, 67-68 

Munich (Germany), 68 

National Academy of Sciences, 53 

National Bureau of Standards, 53 

National Museum of History and Technology, 1 

Navy Department. See U.S. Navy Department 

Nesselwang (Bavaria), 68 

Nettleton, Edwin S., 75-78 

Newell, Frederick Haynes, 83 

Newton, Sir Isaac, 41, 47 

New York harbor, 65 

Nicholas, Czar of Russia, 30 

Oases, 3 

Odometer, 8 

Office of Weights and Measures, 53-54 

Ohio River, 78 

O'Neill (Nebr.), 82 

Orifices, 11, 33 

Ott, A., firm of, 68-69 

Ott, Albert, 69 

Ott current meters, 68-7J 

Ott, Herman, 69 

Ott, Ludwig, 69 

Paddles, 16-21 

Paddle wheels, 21-32 

Padua (Italy), 16 

Paducah (Ky.), 78-79 

Parana River, 50 

Parshall, Ralph Leroy, 40 

Parsons, Dr., 30 

Parsons, William Barclay, 7 

Patent Office (Great Britain), 47 

Patterson, R. M., 53 

Paul, Edwin Geary, 83-84 

Payson, Lt. A. H., 55-56 

Peale, Franklin, 53 

"Penta" contact chamber, 86 

Perkins, Jacob, 53 

Persian windmill, 72, 73 

Perugia (Italy), 6-7 

Philadelphia (Pa.), 51-53, 74 

Philadelphia Mint, 53 

Pisa (Italy), 7 

Pitot, Henri de, 34 

Pitot tube, 24, 33-34, 37 

Poggendorf, 7 

Point Pleasant (Mo.), 65 

Poleni, Marquis Giovanni, 37 

Poncelot, Jean Victor, 57 

Ponts et Chaussees. See Ecole des Pontes et Chaussees 

Pope Urban vm, 7 

Powell, John Wesley, 66 

Price acoustic current meter, 82-83 

Price current meters, 75, 78-87 

Price, William Gunn, 75, 78-87 

Prismatic Club, 73 

Proprietors of Locks and Canals, 28, 31, 54, 56, 60-61, 63 

Q = A, 4, 6-8 

Q = AV, 5, 8 

Quadrant and ball, 15-17, 24 

Quinaria, 4, 33 

Rating of current meters, 50, 53 

Raynolds, Gen. William F., 56, 73-74 

Renaissance, 8 

Repository (Akron, Ohio), 51 

Revy current meter, 50-51, 68 

Revy, Julien John, 50-51 

Riefler, Clemens, 68 

Rio Grande, 66 

Ritchie, E. S., 65 

Ritchie, E. S. and Sons, 66-67 

Ritchie-Haskell direction current meter, 66 

Robinson anemometer, 73 

Rod float, 8-11, 13-14. See also Floats 

Rohwer, Carl, 40 

Roman aqueducts, 4, 6-7, 33 

Rome, 6-7 

Rosedale (Miss.), 81 

Rouse, Hunter, 24, 34 

Royal Institution (London), 53 

Royal Society of Edinburgh, 26 

Royal Society of France, 34, 43 

Royal Society of London, 26, 43, 45-48 

Russia, 30 

Safford, Arthur T., 43, 60-61 

Saint James Park (London), 41 

Saint Petersburg (Russia), 30 

Salusbury, Thomas, 6 

San Francisco, 56, 63-64 

Santorio, Santorio, 16, 20-21 

Saxton current meter, 17, 53-56, 63, 68 

Saxton, Joseph, 51-56 

Schaak, Martin, 3 

Schenevus (N.Y.), 78 

Scott, W. E. and Co., 77 

Secretan (Paris), 56 

Sellers, Coleman, 53 

Sennacherib, 4 

Serviss, J. H., 78 

Sexton, George, 51 

Ships' logs, 14-15, 41-49, 68 

Small Price current meters, 67, 83-87 

Smeaton, John, 45 

Smithsonian Institution, iii-iv, 26, 45, 50, 54, 56, 61, 63-64, 

68, 73-74, 78-79, 82-83, 86 

South America, 50 

"Square inch" method, 33 

S-rotor, 37 

Standards (U.S.), 53 
NUMBER 28 95 

Stearns, Frederick P., 59-61 

Stephenson steam locomotives, 30 

Stimson, Eugene K., 76 

Storrow, Charles S., 30-32 

Stout, Prof. O. V. P., 83 

Subsurface direction meter, 81 

Sudbury River, 59-60 

Survey of the Northern and Northwestern Lakes, 61 

Sussex Street (London), 53 

Technology and Culture, 73 

Tel 'Armarna (Egypt), 2 

Tethered floats, 8. See also Floats 

Thames estuary, 43-44, 47 

Thames River (England), 68 

Tiber River (Italy), 6, 56 

Tolotti, Antonio Sempiterni, 72 

Tolotti current meter, 72-73 

Trasimeno Lake (Perugia, Italy), 7 

Tredgold, Thomas, 37 

Trieste (Italy), 20 

Trinity House (London), 47 

Trowbridge, Prof. William P., 54 

Troy (N.Y.), 81, 83 

Tubing applications, 33-40 

Tutankhamun (Pharaoh), 2 

Turin (Italy), 24 

Union Colony, 76 

United Nations, 40 

University College (London), 53 

University of Nebraska, 83 

University of Notre Dame, 70 

Uruguay River, 50 

U. S. Army, 58 

U. S. Coast and Geodetic Survey, 50, 65 

U. S. Coast Survey, 53-54 

U. S. Corps of Engineers, 58, 63-64, 74-75, 78 

U. S. Department of Agriculture, 40 

U. S. Department of the Interior, 66, 83 

U. S. Geological Survey, 1, 50, 64, 66-67, 69, 78, 82-83 

U. S. International Exhibition, 1876, 74 

U. S. Irrigation Survey, 64, 66-67, 78, 83 

U. S. Lake Survey, 56, 58, 64, 73, 75 

U. S. Mint, 53 

U. S. Navy Department, 66, 78 

U. S. Waterways Experiment Station, 35 

Velocity distribution, 8-11 

Venice (Italy), 16 

Venturi flumes, 40 

Venturi, Giovanni Battista, 11, 37-39 

Venturi tubes, 37-40 

Venturoli, Giuseppi, 56 

Vertical-axis meters, 72-87 

Vertical velocity curve, 16-17, 36 

Vicksburg (Miss.), 81 

Vienna (Austria), 68 

Vitruvius, 4, 22 

Vowles, Hugh F., 73 

Warren, General G. K., 74 

Washington, State of, 83 

Washington, D. C , 53, 83 

Water masters, 1 

Water Resources Branch, 67, 69, 83 

Watkins and Hill (London), 53 

Way-wiser for sea, 48 

Weirs, 40 

Western Canal (Lowell, Mass.), 31 

Westfield (Mass.), 51 

Wheatstone Bridge, 53 

Wheatstone, Charles, 53 

Whistler, George Washington, 29-32 

Windsor (Conn.), 51 

Wolf, Abraham, 7, 13 

Woltman current meter, 68 

Woltman, Reinhard, 21, 49-50 

World Meteorological Organization, 40 

Ximenes, Leonardo, 21 

Yakima (Wash.), 83 

Yoke, Covert. See Covert yoke 

Yugoslavia, 20 

Zammattio, Carlo, 8, 20 

Zurich (Switzerland), 68 

it U.S. GOVERNMENT PRINTING OFFICE; 1974 O—527-777