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6^c 

A Brief History of Geomagnetism 

and 

A Catalog of the Collections of the 

National Museum of American History 

ROBERT P. MULTHAUF and GREGORY GOOD 

SMITHSONIAN INSTITUTION PRESS 
SERIES PUBLICATIONS OF THE SMITHSONIAN INSTITUTION 

Emphasis upon publication as a means of "diffusing knowledge" was expressed by the first 

Secretary of the Smithsonian, in his formal plan for the Institution, Joseph Henry outlined a 

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giving an account of the new discoveries in science, and of the changes made from year to year 

in all branches of knowledge." This theme of basic research has been adhered to through the 

years by thousands of titles issued in series publications under the Smithsonian imprint, 

commencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the 

following active series: 

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Smithsonian Contributions to the Marine Sciences 

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In these series, the Institution publishes small papers and full-scale monographs that report 

the research and collections of its various museums and bureaux or of professional colleagues 

in the world of science and scholarship. The publications are distributed by mailing lists to 

libraries, universities, and similar institutions throughout the worid. 

Papers or monographs submitted for series publication are received by the Smithsonian 

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various Smithsonian museums or bureaux, where the manuscripts are given substantive review. 

Press requirements for manuscript and art preparation are outlined on the inside back cover. 

Robert McC. Adams 

Secretary 

Smithsonian Institution 
SMITHSONIA N STUDIE S IN HISTOR Y AN D TECHNOLOG Y • NUMBE R 4 

A Brief History of Geomagnetism 

and 

A Catalog of the Collections of the 

National Museum of American History 

Robert P. Multhauf 

and Gregory Good 

i - ^ o , - \ 

1 •^.-^ *^x' v_> ^..^^ „„^-

APR; 2, 

SMITHSONIAN INSTITUTION PRESS 

Washington, D.C. 

1987 
ABSTRAC T 

Multhauf, Robert P., and Gregory Good. A Brief History of Geomagnetism and a 

Catalog of the Collections of the National Museum of American History. Smithsonian 

Studies in History and Technology, number 48, 87 pages, 76 figures, 1987.—Geomagnetism (also known as terrestrial magnetism) is the scientific study of the earth 

from the point of view of its magnetic properties. The alignment of a natural or 

artificial magnet in a north-south direction is only the best known of these. Th e 

discovery of other properties, such as the separation of the magnetic poles from the 

geographic poles of the earth and the "dip" of the needle in arctic (and antarctic) 

latitudes, interested the scientifically inclined as early as Columbus. 

Mariners, who had reason to be most interested in the compass, were prominent 

in the study into the 18th century. But as more and more magnetic peculiarities were 

discovered—the apparent movement of the poles, the changes in direction, dip, and 

magnetic strength from year to year and even from day to day, and magnetic 

irregularities apparently connected with other atmospheric phenomena—the aurora 

borealis—the subject was taken over by the scientists. While Alexander von Humboldt, famous as a scientific traveler in the early 19th century, promoted world-wide 

measurement of geomagnetic phenomena, less adventurous scientists occupied themselves with the development of more sensitive instruments and more sophisticated 

methods. Geomagnetism attracted the attention of such leading scientists of the 19th 

century as John Herschel and CF . Gauss. 

One consequence was that this speciality became prominent in the establishment 

of international cooperation in science. In nations, such as the United States and 

Russia, that were both geographically large and underdeveloped, the study of 

geomagnetism assumed unusual importance as a kind of training ground for scientists. 

As time passed, however, it became clear that the numerous scientific questions posed 

by the subject were not to be easily answered. Geomagnetism consequently tended 

in the later 19th century to be absorbed by meteorology, another science whose 

practitioners were accustomed to continuous and tedious measurement with little 

scientific consequence. Geomagnetic measurements also joined gravity measurements 

as conventional duties of the geodetic surveyor. Most interesting, in the later 19th 

century, was the development of instruments capable of making different measurements simultaneously under difficult conditions, and often automatically. 

In the first half of the 20th century geomagnetism became one of the topics 

handsomely supported by the new Carnegie Institution of Washington (which was 

seeking "neglected" sectors of science that were also of international interest). Then, 

as it was found that magnetic "anomalies" were exhibited by petroleum bearing land, 

the subject attracted unprecedented material support. After a generation it began at 

last to seem significant to science at large, in its role in the spectacular development 

of "plate tectonics." Our collection and this history end at this point. 

OFFICIAL PUBLICATION DATE is handstamped in a limited numbe r of initial copies and is recorded in the 

Institution's annual report, Smithsonian Year. COVER: Earth inductor built by the U.S. Naval Observatory 

instrument shop and installed at the magnetic observatory in Sitka, Alaska in 1951. (See Figure 71.) 

Library of Congress Cataloging in Publication Data 

Multhauf, Robert P. 

A brief history of geomagnetism and a catalog of the collections of the National Museum of American 

History. 

(Smithsonian studies in history and technology ; no. 48) 

Bibliography: p. 

1. Magnetism, Terrestrial—History—Catalogs. 2. National Museum of American History (U.S.)—Catalogs. I. Good, Gregory. II. National Museum of American History (U.S.) III. Title. IV. Series. 

QC816.M85 1986 538'.7'0 9 86-600156 
Contents 

Page 

Introduction 1 

Abbreviations 1 

Brief History of Geomagnetism 2 

Magnetic Discoveries to 18Q0 2 

Improvement of Instruments 5 

T h e Era of International Cooperation 11 

North American Research 23 

A "Quiescent Period?" 26 

Early Twentieth Century Research 36 

Catalog of Geomagnetic Instruments 39 

Notes 43 

Bibliography 44 

Figures 31-75 47 

IU 

A Brief History of Geomagnetism 

and 

A Catalog of the Collections of the 

National Museum of American History 

Robert P. Multhauf 

and Gregory Good 

Introduction 

It is the purpose of this publication to acquaint the reader 

with the collections of the Smithsonian Institution (National 

Museum of American History), in this important sector of 

applied physics. In order to put the instruments in context, 

the catalog is introduced by a summary history, of necessity 

something of an original production since it appears that 

only fragments of the history of the subject have been 

written—for example, Mitchell's excellent history (see the 

bibliography), ends with the year 1500 (!). Moreover, since 

our collections come for the most part from American 

sources, the summary history emphasizes the story of geomagnetic research in the United States. It is also biased 

towards instruments and observations. Hence we wish to 

emphasize that our summary is not intended to satisfy the 

need for a general history of geomagnetism. 

Geomagnetism (or terrestrial magnetism, a synonymous 

term) dates as a field of scientific interest from the 16th 

century. Although conventional magnetic compasses from 

that time are not rare, instruments having relevance to 

scientific investigation are rare, if, indeed, any at all still 

exist. Th e early instruments discussed and illustrated in our 

"Brief History" (Figures 1-30) are largely taken from contemporary books in the Smithsonian's Dibner Library. 

From the mid-19th century our collection, while far from 

Robert P. Multhauf, senior historian. National Museum of American History, 

Smithsonian Institution, Washington, D.C. 20560. Gregory Good, assistant 

professor, Program for the History of Science and Technology, West Virginia 

University, Morgantown, W. V. 26506. 

exhausting the range of devices that existed, gives a fair 

indication of the progress of the science. Most of the instruments illustrated in Figures 31-75 represent objects in the 

Smithsonian collection. Number references given with figures in text and in legends refer to catalog entries for 

instruments in our collection. 

We take this occasion to thank the Science Museum of 

London, the Geofysisk Institutt of Bergen, and the National 

Maritime Museum of Greenwich, for allowing us to improve 

our history by illustrating certain important instruments in 

their collections, herein appearing in Figures 9, 15, and 18, 

respectively. Figuies 42, 49, 50, 54, 56, 62, 66, and 73 are 

shown through the courtesy of the Carnegie Institution of 

Washington. 

ABBREVIATIONS 

AdS Konigliche Schwedischen Academie der Wissenschaften (Hamburg, 

1739-1783). This is a German translation of the Handlingar of 

the Swedish Academy of Sciences (Stockholm). 

AJS American Journal of Science 

APS American Philosophical Society 

BAAS British Association for the Advancement of Science 

CIW Carnegie Institution of Washington 

(;S Coast Survey (United States) 

DTM Department of Terrestrial Magnetism, the Carnegie Institution of 

Washingtion 

NMAH National Museum of American History, Smithsonian Institution 

PT Philosophical Transactions of the Royal Society of London 

TM Terrestrial Magnetism and Atmospheric Electricity 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

A Brief History of Geomagnetism 

In pre-Christian antiquity Greek practitioners of "geodesia" (geodesy, land measurement) used astronomical observation to determine the location on the sphere of the 

earth of Alexandria and a few other cities. Th e method 

probably began in observations of the sun and moon but 

ultimately resulted in a "map" of the positions of the "fixed" 

stars, and this in turn facilitated the improvement of the 

terrestrial, geodetic map. Because both were taken to be 

spheres, the terrestrial and the celestial, differences in the 

apparent position of the same heavenly body, as seen from 

two different places on earth, indicated the real difference 

in the terrestrial locations of those two places. 

None of this contributed much, if anything, to the most 

urgent practical need for such information, for the location 

of ships at sea. Ancient mariners hugged the coasts and 

rarely ventured out of sight of land. It was noticed, however, 

that one star appeared to remain stationary while the others 

rotated around it, and that the north-south position (latitude) of a ship could be discovered by observation of the 

height above the horizon of this "north" star. (There is no 

corresponding "south' star, and, in fact, the north star itself 

was some distance from this position in the time of the 

Greek geodecists.) 

When it was noticed that the naturally occurring mineral 

called magnet, or loadstone, aligns itself, when free to turn, 

approximately in a north-south direction, it was realized 

that this gave a means of determining direction in the 

daytime or when the North Star is obscured by clouds. As 

it was also discovered that ordinary iron can be made 

magnetic by rubbing it with a natural magnet stone, magnetized iron or steel needles (only steel retains its magnetism 

for any length of time) were adapted to this purpose and 

the magnetic compass was born (Figure I). It was in use by 

European navigators by the late 12th century. 

Out of these two preoccupations, the geodetic mapping 

of the earth and the use of the magnetic compass in navigation, came the science of geomagnetism. 

Magnetic Discoveries to 1800' 

T h e compass had not been long in use in Europe when it 

was discovered (as early as 1300) that its direction deviates 

a little from "true north," as indicated by observation of the 

North Star. Th e earth appeared to have a magnetic north 

pole slightly distant from the geographic north pole. The 

angle between the two was easily measured, by taking 

simultaneous observations of the direction of the North 

Star and the direction of the compass needle. Th e difference was called variation (later declination; see box, "Terminology"), and was marked on compasses by 1450, to 

enable the user to correct his direction to "true" geographic 

north (Figure 2). 

T h e fact of "variation" also suggested a means of measuring east-west position—longitude. For assuming that the 

magnetic pole, like the geographic pole, is a fixed point, the 

angle between the two would depend on one's east-west 

position. As one traveled around the world these two points 

would at two places be on the same straight line and the 

directions of the geographical and magnetic poles would 

coincide. Between these two places the angle between the 

poles would widen to a maximum and then decrease (see 

Figure 3). It was thought that if these angles were tabulated 

they could be used to determine east-west position. 

T he idea that longitude could be determined by variation 

was one of many schemes put forward to determine longitude, and was pursued with a vigor indicative of the urgency 

to the navigator of the "longitude problem." Variation 

instruments (see Figure 4) combining a compass with a 

device for determining true north by astronomical means 

(i.e., by observing equal altitudes of the sun immediately 

before and after noon) were constructed in the early 16th 

century and in 1585 the Spanish dispatched a Pacific expedition to test such an instrument, which they called a "declinatorium." 

Increased observation, however, led to increased confusion, for mariners seemed unable to verify the observations 

of their predecessors. Th e lines of "no variation," that is, 

where the geographical and magnetic poles are in the same 

straight line, were increased to four by Acosta in 1589, the 

implication being that there are two magnetic axes and 

hence four magnetic poles. By 1674 Robert Hooke was 

theorizing that the magnetic pole is in motion, rotating 

around the geographic pole. But Edmund Halley, who made 

three expeditions in 1698, 1699, and 1702 (the first sponsored by the British government for a scientific purpose) 

supported the idea of four poles. In 1700 he published 55 

observations made between 1580 and 1682, ranging from 

London to New Zealand, and a map on which lines were 

drawn through points of equal variation (Figure 5). They 

correspond to the longitude lines on geographic maps, but 

the lines of equal variation (isogonic lines) showed no corresponding regularity. Some encouragement was found in 

the similarity between Halley's chart and the results of a 

theory of magnetism published by Leonard Euler in the 

1750s. Also in 1744, 1746, and 1757, additional "variation 

charts' were published in the hope of finding some regularity in the annual changes in isogonic lines. But there was no 

profit to navigation and the matter fell into abeyance. 

It had also been noticed that the north end of the magnetic needle tilted downward in the northern hemisphere 

and that the south end dipped downward in the southern 

hemisphere. This could be measured by placing the compass 

in a vertical, rather than a horizontal plane (which of course 

required a different kind of needle support (see Figures 6 
NUMBER 48 

FIGURE 1.—Navigational compass, 15th century, Portuguese, a typical instrument in which a magnetized 

needle is fixed to the underside of a circular card on which the directions are laid out. (Copy, in the 

Smithsonian Institution, of an original in the Museum of the History- of Science, Cambridge University.) 

FIGURE 2.—Drawing of a compass showing the line of declination. (From Peter Apianus, Cosmographicus 

Liber, Landshut, 1524.) 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Terminology 

As in any science, the terms used in geomagnetism 

have changed over time. Typically, the number of technical terms tends to increase until a movement towards 

simplification of the science combines and reduces them, 

after which further development again results in a proliferation of technical terms. Historical writers cannot 

ignore this, but can at least offer some guidance into the 

terminological jungle. 

T he angle between the direction of the magnetic compass needle, its meridian, and "true" (i.e., geographic) 

north was initially called variation, but later came to be 

called declination. A compass specially designed to measure this angle was called a variation compass or declinometer. When it was combined with an instrument for the 

astronomical measurement of geographic north it was 

called an azimuth compass or variation transit. It was also 

often called a theodolite magnetometer, unfortunately for 

logic, since the term magnetometer originally had another meaning (see below). 

T h e tendency of the compass needle to point downward from the plane of the horizon is called dip or 

inclination, and the instrument for measuring this dip 

needle, dip circle, or inclinometer. It was most frequently 

called dip circle. 

T h e strength or force of the earth's magnetism is 

called intensity. The simplest way to measure this is by 

inducing a compass needle to vibrate, by moving it out 

of its normal position, releasing it, and counting the 

numbers of vibrations or "swings" over a given time, as 

it returns to its normal position. This can be done either 

with the declinometer or dip circle. Hansteen's instrument of about 1820, a declinometer with a needle suspended by a thread, was specially designed to measure 

intensity, and was called a magnetometer, a unifilar magnetometer after Gauss and Weber had introduced a decade 

later the bifilar magnetometer, in which the magnet is 

suspended by two (or more) threads so located as to 

constrain the movement of the needle. Th e bifilar magnetometer was also used to measure intensity, but by a 

different, static method. When arranged so as to record 

its data automatically, as by photography, the instrument 

was called a magnetograph. 

As geomagnetic investigation developed, the measurement of variations in declination, inclination, and intensity over time came to be the core of the science. An 

instrument specially designed to measure these changes 

came to be called a variometer. But during the nineteenth 

century such instruments tended to acquire peculiar and 

specific names. Lloyd's adaptation of the dip circle to 

measure intensity by a static method was a vertical force 

magnetometer. Lamont's adaptation of the declinometer 

to the same purpose was an horizontal intensity declinometer, and another of his instruments, in which the needle's 

declination was counteracted by a nearby stationary magnet, was a constant deflection apparatus. Composite instruments, performing more than one function, further complicated the terminology, as in 1842 when Lloyd gave 

the name induction-inclinometer to an instrument that 

measured both dip and intensity. 

and 7). In 1576 Robert Norman, A London instrumentmaker with a wide acquaintance among ships' captains, 

urged the systematic observation of this magnetic phenomenon, which was called "dip." He collected observations that 

led him to conclude that the needle aligned itself parallel to 

the horizon at the Equator and dipped increasingly as it 

approached the poles. But here also, as observations multiplied so did exceptions. The result, as one put it, was what 

one would expect with "an extremely irregular loadstone." 

This theory fell into the same difficulties as did theories of 

variation. Th e result was another chart, showing lines of 

equal inclination (dip), "isoclinic' lines representing magnetic "latitude" as the isogonic lines represented magnetic 

"longitude." Th e first isoclinic chart was attempted by J.K. 

Wilckein 1768. 

Continued observation made matters even worse. Th e 

variation and dip, in places such as London and Paris where 

observations had been made over extended periods, were 

found to change over time. Although possibly known earlier, it was noted in 1682 that variation varied (an awkward 

phraseology that led many to replace the term "variation" 

by "declination") from day to day; and in 1722 this was 

confirmed in careful observations made by the London 

clockmaker George Graham, with a specially made compass 

having a needle of 12.2 in/30.1 cm in length, protected by 

a rectangular brass box. By 1790 it was clear that both 

declination and dip varied with the season and the time of 

day. Agreement was still lacking on the location of the 

magnetic poles. Those who accepted a single north pole 

gave it, in English, French, Russian, and Swedish sources, a 

latitude varying between 59 and 75 degrees. But there was 

no shortage of observations, Captain James Cook made 

magnetic observations on his epochal voyages, 1768-1779. 

T he French explorer E.P. de Rossel made observations in 

1 791 -1794 . Towards the end of the century the celebrated 

French naturalist Count Buffon published a volume on 
NUMBER 48 

Geographic Longitude 

Magnetic Longitude 

Finding Longitude By Magnetic Declination 

FIGURE 3.—This sketch illustrates how the angle between the geographic 

and magnetic poles changes with the position of the viewer. (Drawn by 

Mark Kemp.) 

magnetism containing 234 pages and listing over 7,000 

observations made between 1767 and 1780. 

Improvement of Instruments^ 

However distressing the inconclusiveness of all this was 

to the navigator, it made the subject even more interesting 

to the scientist. To test the possibility that geomagnetism 

varies with altitude, Benedict de Saussure made observations in the high Alps, for which he constructed a unique 

instrument designed to measure the effect of magnetism on 

an iron ball fixed to a pendulum. In 1794 magnetic measurements were made in the Saxon mines at Freiberg. The 

possibility that the difficulty lay, at least in part, in the 

imperfection of the instruments used was naturally explored. Although, as has been noted, special instruments 

for variation (declination) and dip (inclination) had existed 

since the sixteenth century, most of the observations that 

revealed the complexity of terrestrial magnetism were made 

with an ordinary ship's compass. But in the last half of the 

eighteenth century the improvement of the compass was 

taken up by the scientist, who increasingly exhibited at that 

time a virtual fanaticism for precision measurement. 

In France, Duhamel (probably H.L. Duhamel du Monceau) published in 1750 an account of improved magnets 

and in 1772 a description of his magnetic observatory for 

which a Paris optician named Antheaume constructed six 

declination compasses, with needles from 6 to 15 inches in 

length, and of varying weights, mounted on stone pedestals 

placed in groves (bosquets) in the park of Denainvilliers. A 

scale six feet long, made of close-grained limestone, was 

located 52 feet from the compasses, at the same level so 

that their directions could be observed by looking along 

sights mounted on the needles. Every precaution was taken. 

The compasses were enclosed to protect them against the 

atmosphere, with portholes of horn to avoid any electrical 

effect of glass, and their supporting pedestals were made 

without mortar to eliminate the possibility of included iron 

(see Figure 8). Duhamel does not tell what use he made of 

what must have appeared to his neighbors to have been a 

sculpture garden. 

British instruments, like British institutions at that time, 

were simpler, and the variation/declination compass "in the 

Royal Society's House" in London, as described by Henry 

Cavendish in 1776 (see Figure 9), was simpler. It too was 

placed in a garden to protect it from the influence of iron 

used in buildings (although Cavendish found later that it 

functioned just as well in a room). This instrument, which 

had a needle made by the well known London instrumentmaker Jonathan Sisson, was used for twenty years, its results 

being published in 1806. It is clear that by this time geomagnetic instruments had become staples of the instrumentmaker's trade. The Royal Society's dip needle was made by 

Edward Nairne, an instrument-maker who was a Fellow of 

the Society, and who made a variation compass and dip 

needle for Harvard College in 1765. Still at Harvard, these 

may be the first such instruments brought to North America. George Adams advertised similar instruments in 1785, 

and the third edition of Tiberius Cavallo's Treatise on Magnetism (1800) was prefaced with an advertisement for a 

complete set of instruments by W. &: S. Jones. 

The needle was the crucial component, and needles were 

moved from one instrument to another and the same 

needles were tested in London, Paris, and elsewhere. Cavallo, although convinced that some mathematical regularity governed terrestrial magnetism, was pessimistic of the 

possibility of discovering it, because of "the irregularity of 

the motion of the magnetic poles.'' 

Much ingenuity was expended on the reduction of friction on the pivot point of the needle. Cavallo wrote of "a 

new suspension" in which the needle was suspended by a 

horse hair. Thus he would appear to have been unaware 

that this kind of suspension had been virtually "perfected" 

in France over two decades earlier. Charles Coulomb, a 

French military engineer, undertook the improvement of 

the compass in 1776, in pursuit of a prize offered by the 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 4.—Instruments for measuring declination (variation). Left, above: 

magnetic compass attached to an armillary sphere. (From Mark Ridley, 

Short Treatise of Magnetical Bodies and Motions, London, 1613.) Left, below: 

magnetic compass with quadrant attachment. (From Petrus van Musschenbroek, Physicae Experimentalis, Leiden, 1729.) Right: "variation transit," by 

Peter Dollond, about 1800. (From Encyclopaedia Britannica, 8th edition, 

volume 14(1857)). 
NUMBER 48 

/ W / - J 

FIGURE 5.—"Chart of the lines of equal magnetic variation," by Edmund Halley, 1701. (Reprinted from 

TM, 1 (1896).) 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 6.—Magnetic "dip needle,' mounted on a conventional compass. 

(From Mark Ridley, Short Treatise of Magnetical Bodies and Motions, London, 

I6I3.) 

Academic des Sciences in Paris. In the memoir that won 

the prize (1777) Coulomb described a compass suspended 

by a thread, instead of supported on a pin (Figure 10). 

Although he did not originate this idea. Coulomb was the 

first to pursue it scientifically, working out a mathematical 

formulation for the forces (of torsion) involved in the twisting of threads and wires, with, as a by-product, the invention 

of the torsion balance. 

Coulomb used the balance to measure many small forces, 

including those of terrestrial magnetism. By 1777 his 

thread-suspended compasses had been adopted by the Paris 

observatory and improved by J.D. Cassini. Coulomb and 

Cassini were not instrument-makers and the instruments 

may have been made by Etienne Lenoir (1744-1832), one 

of the very few French instrument-makers of the time whose 

skill compared with that of the English makers mentioned 

above. 

Even "identical" magnetized needles varied in strength, 

and the same needle often varied in strength from one time 

to another. Some wondered if the strength of terrestrial 

magnetism could not vary similarly, thus accounting for 

some of its irregularities. On this assumption, as pure science replaced navigation as the objective of studies in geomagnetism, a new measurement was added to declination 

and inclination, namely "intensity,' a quantitative measure 

of magnetic force. A method was introduced by J.C. Borda 

in 1778 for comparing intensities at various places by measuring the rate of vibration of the needle. Tha t is, advantage 

was taken of the fact that the compass needle aligns itself 

magnetically, not instantaneously, but by oscillating back 

and forth across the line (magnetic meridian) on which it 

finally settles. Measurement of intensity assumed that the 

needle would oscillate about its meridian more quickly as 

the earth's magnetic intensity was greater. However, because this rate of oscillation also depended on the magnetic 

strength of the needle, each instrument yielded a different 

value. Intensities determined by this method were usually 

called "relative" because they were relative to a particular 

needle. For this reason, a single needle was often used in 

different places to compare intensities. Two or more 

needles could also be oscillated together in one location to 

obtain a temporary standard of comparison. 

The vibration of the needle of the dip-needle/inclinometer was considered analogous to that of the pendulum used 

in measuring the force of gravity, and as in the latter case, 

forces were compared as the square of the number of 

oscillations made in the same time. They were also relative. 

Such measurements were made on the de Rossel voyage of 

1791-1794 and by Alexander von Humboldt on his expedition to South America of 1798-1804, using an instrument 

made by Lenoir. In the latter year J.L. Gay-Lussac and J.B. 

Biot made intensity measurements from a balloon over 

Paris, also with instruments by Lenoir. 

These observations established that the intensity of terrestrial magnetism increased with latitude. However, the 

dip needle was soon found inadequate for this measurement, due to pivotal friction, and the suspended needle of 

the declination instrument came into favor. Because an 

oscillating horizontal needle measures the horizontal intensity only, while the dip needle measures total intensity (see 

box, "Measurements and Calculations"), the latter method 

required a simple trigonometric transformation. Humboldt 
NUMBER 48 

C_^ ^ 

FIGURE 7.—Instruments for measuring magnetic "dip." Left: Petrus van 

Musschenbroek called this apparatus an "inclinatorium." (From Physicae 

Experimentalis, Leiden, 1729.) Right, above: demonstration apparatus. 

(From J.A. Sigaud-Lafond, Description et usage d'un cabinet de Physique 

Experimentale, Paris, 1755.) Right, below: this elaborate apparatus, also 

illustrated by Musschenbroek, was made by John Sisson, of London. 
10 

SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 8 -Geomagnetic apparatus of Duhamel, which was installed in the Pare de Denamvilliers, Pans, 

in 1750 Figs 1-3 and 9-12 show declination compasses. Fig. 8 shows their position relative to the scale 

(fig. 13), which is 52 ft/15.8 m distant. Figs. 15, 16 show the inclinadon (dip) needle. (From the Memoires 

de I'Academie Royale des Sciences, Paris, for 1772.) 
NUMBER 48 11 

FIGURE 9.—"Variation compass" made by George Adams of London, in the Science Museum, London, 

with whose permission this illustration is reproduced. It appears to be virtually identical to the Royal Society 

instrument used by Henry Cavendish, and described by him in the Philosophical Transactions of the Royal 

Society, Volume 66 (1776). 

and Gay-Lussac used this method in Italy in 1805-1806, 

using a needle suspended by a silk thread. 

The Era of International Cooperation' 

Humboldt's conclusion, from his South American observations, that magnetic intensity varies from place to place, 

established geomagnetism as a subject particularly deserving 

the attention of the scientist. Indeed, one scientist called it 

"the great physical mystery' left unanswered by Newton. 

This ended the era when geomagnetism was an incidental 

study, primarily pursued by perambulating explorers, and 

began another in which the subject was primarily a scientific 

discipline situated in "observatories," many temporary but 

an increasing number permanent. Humboldt's research 

symbolized this change, for after his visit to Italy he settled 

himself, except for a brief excursion to Siberia (in search of 

a magnetic pole), in Paris and Berlin, where he established 

geomagnetic observatories on several occasions. For over 

half a century Humboldt lent his great reputation to the 

promotion of the scientific study of the earth, and particularly to terrestrial magnetism. 

In England, George Gilpin, Secretary of the Royal Society, published in 1806 the observations made over thirty 

years with the antiquated instruments of the Society. In 

1813 Mark Beaufoy, a wealthy patron of the Society, established an observatory at Bushey Heath (Hertfordshire) 

where he made frequent observations for nearly a decade, 

using a declinometer similar to that of the Royal Society 

but incorporating a theodolite for celestial observations 

(Figure 11). In 1818-1820 Edward Sabine used instruments 

made by Nairne and Blunt on three Arctic expeditions, and 

a Russian naval expedition of 1826-1829 used instruments 

obtained from England. Th e firm of Dollond, by this time 

the best known English instrument-makers (thanks to their 

development of the achromatic lens), now appears as makers 

of magnetic instruments, including a metal-free instrument 

(made of mahogany and ivory) with a suspended needle, 

designed for the measurement of daily variation (Figure 

12). 
12 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

z-^,/. 

FIGURE 10.—Coulomb's thread-suspended magnets, 1785. From Memoires de I'Academie Royale des Sciences 

(Paris), for 1785.) Above: instrument for determination of the magnetic meridian. Th e magnet is 18 pouce 

(inche.s)/46 tm in length. Right: instrument for the measurement of "variation" (declination). 
NUMBER 48 13 

^W6I' 

J'w 6. 

Fz^.6, 

It was the observation of daily (diurnal) variation that 

inspired Beaufoy's activity, and subsequently that of other 

observatories. At Paris, D.FJ. Arago, who, under the influence of Humboldt, had become involved in the observations 

there, reportedly took 52,599 measurements betw?een 1820 

and 1835. 

Under the patronage of Humboldt and Arago, the young 

Paris instrument-maker, H.P. Gambey (1787-1847), w^as to 
14 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

North West 

Measurements and Calculations 

In the accompanying diagram, D and I represent the 

angles of declination and inclination, which can be measured directly. A magnetic needle suspended from its 

center of gravity would lie along line FT. Th e lines FH, 

FV, and FT represent the horizontal, vertical, and total 

intensities of the force that returns a deflected needle 

back to this neutral position. Hence, the ratio of the 

vertical intensity to the horizontal intensity equals the 

tangent of the inclination (FV/FH = tan I). Th e total 

intensity FT combines these forces according to the 

familiar parallelogram offerees (FT = FH.sec I or FV.csc 

I). Because the horizontal intensity could be measured 

with greater precision than either the vertical or total 

intensity in the mid-19th century, it was the preferred 

intensity measurement. (Diagram by Mark Kemp.) 

become the most important French maker of geomagnetic 

instruments and the producer of what was long considered 

the "classic" magnetometer (Figures 13 and 31). Arago's 

account of the work in Paris reveals the spread of Gambey 

instruments through the western world. By 1818 Arago 

was using a compass of William Ritchie's design, made by 

Gambey, which was destined for "the University of Cambridge in America" (Harvard, which still has the instrument). In 1822 Arago was again observing with a Lenoir 

compass, which was then to go around the world with the 

explorer L.I. Duperry, and with a Gambey compass destined 

for the Finnish University at Abo. In 1829 it was a Gambey 

compass destined for the University of Freyberg (Freiberg). 

By 1831 he had a Gambey compass owned by J.F. Encke, 

Director of the astronomical observatory in Berlin, as well 

as a Gambey instrument destined for Frederick Rudberg of 

Stockholm. Although instruments used in North America 

were usually English, the military academy at West Point, 

which was principally supplied with French scientific instruments, had a dip circle by Gambey. A declinometer by 

Gambey (Figures 14 and 32) was used by Alexander Dallas 

Bache in the 1840s. 

With the termination of the Napoleonic wars Humboldt 

undertook to promote government support for observations 

of terrestrial magnetism. Th e first fruits were a series of 

French naval expeditions that aimed to sail along the "magnetic equator,' that is, the line of no inclination, which 

Humboldt had discovered in Peru. In 1829, on the occasion 

of his brief expedition to Siberia, Humboldt addressed to 

the Academy of Sciences in St. Petersburg a plea for the 

establishment of geomagnetic observations in the Russian 

Empire. Th e proposal was accepted and acted upon with 

remarkable alacrity. Within three or four years he addressed a similar proposal to the British, in a letter in which 

he reported having received favorable responses from 

France, Prussia, Hannover, Denmark, and Russia, and 

noted that permanent stations had already been established 

at Paris, Berlin, and the Freiberg (Saxony) mines, Copenhagen, Iceland, St. Petersburg, Moscow, Kazan, Barnoul (at 

the foot of the Alta mountains), Nertschinsk (near the 

frontier with China), Nicolajeff (Crimea), and Peking (in 

"the garden of the Greek monks"). Humboldt recommended the establishment of such observatories in the farflung British dominions, particularly in the Cornwall tin 

mines, at the Cape of Good Hope, and in Canada (he warned 

against Montreal because of its iron roofs). 

Humboldt's recommendation was presumably helpful, 

but the British were already among the most active observers in Europe and a joint petition by the British Association 

for the Advancement of Science and the Royal Society were 

crucial in securing government support. Led by Edward 

Sabine (1788-1883), the British Association, from 1831, 

made terrestrial magnetism one of its special interests. 

Sabine had found reason, in consequence of his arctic 

expeditions of 1818-1820, to contradict the supposition 

that magnetic intensity would be greatest near the poles. 

His claim was confirmed in 1832 by Captain J.C. Ross, who 

had taken a Jones dip circle, among other instruments, to 

the magnetic latitude 89 degrees, 41 minutes. Ross then 

joined Sabine and Humphrey Lloyd in making observations 

in Ireland, which were published, along with the observations made in England and Scotland in 1836. This effort 
NUMBER 48 15 

FIGURE 11.—"Variation compass" used by Beaufoy at his observatory at Bushey Heath, Hertfordshire, as 

described and illustrated by Beaufoy in Annals of Philosophy, volume 2 (1813). It differs from the Royal 

Society instrument (see Figure 9) principally in the incorporation of a "transit telescope." 

constituted one of the first detailed regional magnetic surveys. 

T he attempt to establish systematic observations was but 

one of several focal points of terrestrial magnetic work in 

the early nineteenth century. Others were the search for 

the poles, both north and south, the improvement of instruments and of theory. One prominent participant was Christopher Hansteen (1784-1875), a Norwegian who had become interested in magnetism under the influence of 

Oersted in Copenhagen and who won a prize that had been 

offered by the Danish Academy of Sciences in 1811 for a 

theory of geomagnetism. Hansteen's theory assumed the 

existence of two magnetic axes, and he went off to Siberia 

in 1828, with a Dollond dip circle, to look for a second 

North Pole. Hansteen, who had been a professor at the 

Norwegian University at Christiana (Oslo) from 1814, also 

attempted to found an observatory there and occupied 

himself with the improvement of the instrument for measuring magnetic intensity. He was to be most successful in 

the latter, and established a method that was to be standard 

for decades. Hansteen's method aimed to circumvent the 

peculiar problem that the force of a magnet cannot be 

referred to a single point but involves two points, the north 

and south poles, and that these are themselves not precisely 

identifiable points. To some degree this could be offset by 

using long magnets, thus separating the poles. Hansteen's 

declination instrument, called a "magnetometer,' consisted 

of a magnetized steel cylinder about 30 inches long and 0.1 

inch in diameter (which he obtained from Dollond in London), protected by a wooden box and suspended by a silk 

thread in a vertical wooden tube 56 inches long. Th e needle 

was set in motion by bringing an iron rod in its vicinity, the 
16 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 12.—"Diurnal variation instrument" of (George) Dollond, with thread-suspended needle, about 

1825. Th e test-tube shaped pieces are microscopes. (From Encyclopaedia Britannica, 8th edition, volume 14 

(1857).) 

time required for 300 vibrations being taken as the measure 

of intensity (Figure 15 shows a surviving Hansteen magnet 

of smaller dimensions). 

In 1818 Humboldt succeeded in recruiting to the field 

C F . Gauss, a Gottingen professor who, at 51, had already 

for a generation been the most prestigious mathematician 

in Europe. In the next decade Gauss brought to Gottingen 

the 27-year-old physicist, W.E. Weber, and the two studied 

geomagnetism for almost ten years, until 1837 when Weber 

was discharged from the university for resisting political 

pressure on the faculty. In 1833 Gauss, the theoretician, 

published his Intensitas vis magneticae terrestrius ad mensuram 

absolutam revocata (The Intensity of Magnetic Force Reduced to Absolute Measure), an epochal work in that it 

represented the first attempt to measure a non-mechanical 

quantity (i.e., magnetism) in terms of what were in the 

canon of Newtonian science "absolute' units, namely mass. 

distance, and time. Th e experiments that went with this 

theory, Weber's particular contribution, were conducted in 

a new magnetic observatory constructed at Gottingen. 

T h e observatory occupied an oblong room 36 feet long, 

in the direction of the magnetic meridian. In the main 

instrument the "needle" was a bar 23.62 inches long and 

weighing 3.75 pounds. It was ultimately increased to 25 

pounds and the supporting "thread" correspondingly 

strengthened, being either a bundle of threads or a wire, 

about six feet long. To measure intensity the measurement 

of vibrations was followed by a second step in which the 

magnetic moment of the bar was taken into account (see 

box, "Gauss, Weber, and Absolute Values,' and Figure 16). 

T h e result was a value of the earth's magnetic intensity that 

could be replicated by all instruments and magnetic needles. 

In its simplest form the Gauss magnetometer was "read" 

by putting a mirror on the end of the magnet, a method 
Fifr. 50'J. 

Fig. 510. 

•612. Fig. 513. 

FIGURE 13.—Some instruments commercially available in the mid-19th century. (From Catalogue des 

Instruments of the Paris maker, Deleuil (1863).) 509, compass for diurnal variation (similar to No. 1, Figure 

3 1 , in the present collection). 510, unifilar magnetometer for intensity measurement (similar to No. 5 in 

the present collection). 511, inclination compass with vertical circle (i.e., a dip circle, similar to the Froment 

and Barrow instruments, Nos. 29 and 30, Figure 60 in the present collection). 512, Gauss unifilar 

magnetometer, with observing telescope. 513, Gauss bifilar magnetometer. 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 14.—Declination compass by Gambey. No. 2 in this collection (Figure 32 in this study) exemplifies 

this type of instrument. (From A. De la Rive, A Treatise on Electricity, London, 1858.) 

introduced in 1826 by Johann Poggendorff. Th e scale, 

located beneath the observing telescope, was viewed 

through its reflection from the mirror. Such an arrangement was vulnerable to the influence of air currents on the 

magnet and to the time taken for the magnet to settle on 

its meridian, and the instrument was soon modified to 

counter these difficulties. Th e magnet was placed within a 

protective box and the mirror was placed on the supporting 

"thread" outside the box. Th e poles of the magnet were 

encased in copper, which had a damping effect on its 

movement. In a modified version intended to indicate 

changes in horizontal intensity, the magnet was supported 

by two threads so located as to hold it approximately at 

right angles to the magnetic meridian. This arrangement 

was called the "bifilar" magnetometer (see Figure 13). 

Weber had the ingenious idea of putting to use the then 

new discovery of electromagnetic induction. A circuit of 

wire, located near one end of the magnetometer, was car-
NUMBER 48 

19 

FIGURE 15.—An example of Hansteen's apparatus for measuring diurnal 

variation of the needle, preserved in the Geofysisk Institutt, Bergen University, Bergen, Norway. The instrument, viewed from above with the 

cover open, has a cylindrical magnet, made by Dollond, 2.8 in/72.8 mm 

long. The thread suspension is about 5.8 in/150 mm long. The instrument 

resembles that drawn in Hansteen's account of his work in Siberia (Resultat 

Magnetischer, Astronomischer und Meteorologischer Beobachtungen-auf einer 

Reise nach dem ostlichen Siberien in denjahren 1820-1830. Christiana, 1863.) 

ried to the astronomical observatory some distance away. 

Movement of the magnet induced a current in this circuit 

that moved a magnetic needle in the observatory. This 

"telegraphic signal" was the beginning of German work on 

telegraphy. 

Gauss and Weber supplied copies of their instruments, 

made by Breithaupt of Cassel and Meyerstein of Gottingen, 

to other observatories in Bonn, Cracow, Dublin, Freiberg, 

Greenwich, Kazan, Leipzig, Marburg, Milan, Munich, Naples, and Upsala. They then organized the magnetic observatories of Europe, of which there were 23, into an 

association (Magnetische Verein) that issued published reGauss, Weber, and Absoulute Values 

Gauss and Weber replaced conventional needles with 

long magnetized bars, in order to minimize the mutual 

influence of the north and south poles. They then addressed the problem that measurements of "magnetic 

force" (intensity) involve not only the magnetism of the 

earth but the magnetism of the compass needle itself, as 

well as its shape and weight, all of which vary from one 

compass to another. They solved this problem by making 

two different experiments, each of which led to an equation, and showing that these equations could be combined to eliminate as factors the magnetism, shape, and 

weight of the bar. Th e first experiment was simply the 

observation of the vibration of the bar. This gave the 

product of the earth's horizontal intensity and that of the 

bar (A = H X f). In the second experiment a second 

magnetized bar was placed in the stirrup and the first 

magnet was placed on a line perpendicular to the magnetic meridian. This magnet caused the suspended bar 

to deviate from its normal position by a certain amount, 

and the angles and distances involved indicated the ratio 

of the intensity of the same magnet (now stationary) to 

the earth's horizontal intensity (B = f/H). By combining 

the equations they arrived at a number for the earth's 

magnetism in "absolute" units, mass, distance, and time 

(H = B/A). 

Gauss's method is indeed elegant on paper, but as 

Bauer noted in 1914, the procedure required about an 

hour and a half to accomplish. This, he said, posed the 

most serious problem to itinerant observers. A further 

difficulty was the fact that the pocket chronometers used 

in the vibration procedure were too delicate for rugged 

expeditions. ^ 

suits in six volumes between 1836 and 1841. After Weber's 

departure. Gauss finished his theoretical work, with a mathematical theory that contradicted and replaced the theory 

of Hansteen. It was based on the assumption that the 

terrestrial magnetic force is the collective action of all of 

the magnetized particles of the earth's mass, attracdng and 

repelling each other with forces inversely proportional to 

the squares of their mutual distances, according to "an 

infinite theory of spherical functions." Gauss then lost interest in geomagnetism; he left not only a new theory, but he 

and Weber endowed their successors with some new instruments and, perhaps most important of all, with a clearer 

definition of what measurements were essential to a scientific analysis of geomagnetism. 

The improvement of instruments continued. Th e Robinson instruments that had been used in the survey of Ireland 

were modified by Ross, the dip circle with a better pivot 

and the magnetometer by modifying the needle according 
20 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 16.—The Gauss-Weber magnetic laboratory at Gottingen, showing the apparatus for declination. 

(From Becquerel, Traite Complet de Magnelisme, Paris, 1846.) 

to "Mayer's principle"—the latter referring to the rectification of the inevitable imperfections of fabrication through 

the addition to the needle of an adjustable weight for 

compensation. It had been introduced by Tobias Mayer in 

1814. In Scotland R.W. Fox published, in 1835, results of 

observations with his "dipping needle deflector (Figure 

17), which measured variation, dip, and intensity, under 

various arrangements. Perhaps the first attempt at a "universal" instrument, it found wide use for the next fifty 

years. Because it increased the accuracy of measurements 

at sea, the analysis of instrumental errors and the refinement 

of observational procedures were greatly facilitated by Fox's 

circle. 

T h e innovations of Humphrey Lloyd were most lasting, 

notably his "induction-inclinometer" and his "vertical force 

magnetometer" (also called "balance-magnetometer"). In 

the former, which was a declination instrument used indirectly to measure inclination, a twelve-inch bar of soft iron 

was mounted vertically adjacent to a three-inch suspended 

needle. Th e bar becomes a weak magnet under the influence of the earth's magnetism and deflects the needle 

accordingly. Th e tangent of the resulting "angle of deflecFIGURE 17.—Fox's "dipping needle defiector," introduced in 1835. (From 

Annals of Electricity, 3 (1839) PI. V, fig. 47.) [Reference: T.B. Jordan, 

"Description and use of a dipping needle defiector invented by Robert 

Ware Fox," Ibid, pages 288-297.] 
NUMBER 48 21 

tion" is a measure of its inclination and its intensity. The 

vertical force magnetometer (Figure 18) embodied a 

"needle" resembling the beam of an ordinary chemical 

balance. Its tendency to dip was counteracted by a movable 

counterweight, and, by restoring its horizontal position with 

this weight, data was obtained that permitted the calculation 

of both dip and intensity. Moreover it indicated directly 

changes in the vertical force, and could be used to measure 

these changes from day to day or hour to hour, a measurement that was facilitated by its incorporation, by 1850, into 

the photographic self-registering magnetograph. 

T he principal German improver of instruments, Johann 

Lamont, was, curiously enough, a native of Scotland, from 

which he departed at the age of twelve as a pupil of the 

"Scottish Foundation" in Regensburg. He remained permanently in Germany, where he was eventually knighted. 

An astronomer with a particular interest in geophysics and 

in instruments, he found the instruments of Gauss and 

Weber erratic, in geomagnetic measurements made on a 

Bavarian mountain (Hohenpeissenberg), and became their 

severest critic. In 1835 Lamont became Director of the 

Bavarian astronomical observatory at Bogenhausen, to 

which was added, four years later, a new magnetic observatory in Munich. Ther e he devised for geomagnetism a new 

"system . . apparently resting on laws, although not apparently connected with the form or peculiarities of the surface 

of the globe." It "fitted powerfully to excite the spirit of 

research," which he pursued in a laboratory that was ultimately credited with no less than 45 innovations in magnetic 

instruments. Many of his innovations, like those of Lloyd, 

related to the incorporation of fixed iron bars or permanent 

magnets, whose relationship to the movable magnetic 

needle gave data for the description of the geomagnetic 

situation in absolute units. Lamont also reworked the basic 

magnetometer of Gauss and Weber and finally reduced 

their 25 pound "needle' to one weighing a single gram. 

T he British Royal Astronomical Observatory at Greenwich had also begun the installation of instruments for 

geomagnetism in 1837, and in the next year the BAAS 

resolved to petition the government for 400£ to support 

magnetic observatories "in the various parts of the British 

dominions." The request was approved, and by 1840 observatories were established (although in most cases they 

were not yet functioning) at several of the locations proFIGURE 18.—Lloyd's "vertical force magnetometer" (or "balance magnetometer"), introduced about 1842. 

This example is in the National Maritime Museum, Greenwich, England, through whose courtesy it is 

reproduced here. 
22 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

posed: Toronto, the Cape of Good Hope, St. Helena (a 

south Atlantic island), and Van Dieman's Land (Tasmania). 

T h e project had also inspired a number of others. Dublin 

had set up an observatory for Lloyd; the East India Company had established four; the "universities of Philadelphia 

and Cambridge" (Girard and Harvard Colleges) had established observatories in the United States; and even two 

Indian Maharajahs had established observatories. Others 

were set up, or planned, by the governments of Algeria, 

Bavaria, Belgium, Egypt, Prussia, and Spain. Th e Russian 

government now proposed no less than ten. Thus the British 

example reinforced Humboldt's injunctions to give terrestrial magnetism a firm footing as a subbranch of physical 

research. 

About 1840 the Royal Society published Instructions for 

the Use of the Magnetic and Meteorological Observatories and 

for the Magnetic Surveys (we have used a revision of 1842), 

and in 1844 appeared a more comprehensive publication 

from the British Admiralty, Magnetical Instructions for the 

Use of Portable Instruments Adapted for Magnetical Surveys 

and Portable Observatories, by Lt. C.J.B. Riddell, the first 

Director of the Toronto Observatory. The instruments 

proposed by the former publication can best be identified 

in the following tabulation. 

Instrument 

declinometer 

bifilar magnetometer. 

unifilar magnetometer. 

inclinometer 

balance magnetometer. 

Description 

thread suspended 

magnet. 

type of Gauss 

same as declinometer. 

no description 

Lloyd's (see 

above, p. 21) 

Magnet 

15" bar 

same as declinometer. 

12" and 9" magnets. 

12" needle 

Purpose 

absolute declination. 

variation of intensity. 

absolute horizontal intensity. 

inclincation 

(dip) 

variation of vertical intensity 

It might be supposed that Riddell's Magnetical Instructions, stressing portability, would be simpler. However, after 

he notes that a magnetic survey can be made with only two 

instruments, a dip circle and a magnetometer, he goes on 

to describe a bewildering variety of instruments—at least 

with respect to their names. This is perhaps sufficiently 

indicated by his immediate observation that the "magnetometer" can either be a "theodolite magnetometer" or a "portable unifilar magnetometer with a portable declinometer." 

They were commercially available (see Figure 19) from 

Thomas Jones and (Henry) Barrow of London, and from a 

Mr. George of Falmouth. 

Riddell also printed the forms for recording observations, 

which were to be taken at times rigorously specified in 

terms of Gottingen mean time. "Regular observations" were 

taken hourly, not only of all instruments (except for the dip 

circle, which was observed twice weekly) but of several 

meteorological instruments, the whole to be accomplished 

within the two minutes before and after the hour. "Term 

observations" were taken monthly, and "extraordinary observations" when marked change was noticed, especially 

during the aurora. "Absolute determinations" were made 

on occasion, as a check on the "differential instruments,' at 

least once each half-year in a fixed observatory. 

Thus the single observer, who is the object of the above 

instructions, can be pictured as busy, and a producer of 

paper records that put those of eighteenth-century observers beyond the pale. Th e primary object was the determination of absolute values of declination, inclination, and 

horizontal intensity at different stations, a calculation that 

required three or four hours. 

This was roughly the apparatus supplied to Lt. Lefroy in 

1842 for the magnetic survey of Canada, which ranged 

from Montreal to Lake Athabasca and ended at Toronto 

where a permanent observatory was established. Lefroy 

replaced Riddell as Director, and the names of the instruments do not correspond precisely to those in Riddell's 

Instructions. Indeed, two descriptions of Lefroy's instruments do not correspond with each other. One mentions 

the inclusion of a Gambey inclinometer and a Fox inclinometer of seven inches diameter. A dip circle made by George 

of Falmouth, as designed by Fox, mentioned in the other 

account, may be the same instrument, but this account also 

mentions a portable declinometer of Weber's construction 

(which was later replaced by an instrument designed by 

Riddell and made by Jones). 

As part of the British enthusiasm for magnetic studies, 

the Royal Observatory at Greenwich had already constructed a magnetic observatory in 1837. It possessed a 

"meridional magnet" and, by 1840, a bifilar magnet for 

variations of horizontal force. Th e former was based on a 

Simms theodolite and incorporated a two-foot-long magnet 

made by Meyerstein of Gottingen. Th e instruments would 

appear to be those specified by Gauss, and to have been 

themselves the prototypes of those specified for the new 

observatories. 

As is evident from the instructions published by the Royal 

Society and the British Admiralty, increased accuracy of 

measurement was by the mid-nineteenth century no longer 

the sole focal point of research in instrumentation. Scarcely 

less important was measurement of short term (diurnal) and 

long term (secular) changes, which were found to occur 

wherever magnetic measurements were made for any 

length of time. Riddell's busy observer was expected to keep 

track of them. However, this new, arduous, and recordinflating task virtually coincided with its solution, the development of automatic photographic recording. In 1846-

1847—scarcely a decade after the introduction of photography—Charles Brooke of the Greenwich Observatory and 

Francis Ronalds of the Kew Observatory introduced apparatus for the photographic registration of thermometers 

and barometers, and very shortly afterward of the position 

of the needle in geomagnetic instruments (see Figure 20). 
NUMBE R 48 23 

98 

PRICES OF INSTRUMENTS. 

Instrument<* made by Mr. Thomas Jones, 62, Charing Cross. 

£. s d. 

Portable Declinometer.f with Apparatus for 

experiments of deflection, and Stand . 14 0 0 

Ditto with an additional table top, capable of 

carr)'ing both the Theodolite and Declinome'er 15 2 0 

2 Five-inch Altitude and Azimuth instrument, 

divided to 30", with transit a.xis, diagonal 

eye tube, Lamp, &c. .. . 21 10 0 

Triangular Stand .. . ... . 210 0 

3. Portable Unifilar MagnetometerJ and Stand . 22 10 0 

4. Theodolite Magnetometer and Stand . . 30 0 0 

5. Portable Declination Magnetometer and Stand 12 0 0 

6. Portable Bifilar Magnetometer, (with socket 

arms and two soft iron cylinders, to enable it 

to be used as an Induction Inclinometer, 

if so required,) and Stand 19 10 0 

1. Induction Inclinometer, for a fixed or portable 

observatory 150 0 

Portable Stand 210 0 

Additional reading Telescope and Scale to 

be used in a fixed observatory .. . 3 13 6 

8. Observatory Unifilar Magnetometer, with Apparatus for experiments of deflection and 

vibration, reading Telescope, long scale, &c.. 14 10 0 

9. Observatory Bifilar Magnetometer, reading 

Telescope, &c. . . 11 0 0 

• The instrnments which are to be ordered from this list for a nwgTutic mrviy are 

Xos. 1 and 2, Nos. 1. 2. and 3, or No. 4 ; for a mngnchc rurvey and complete 

forlahle ubierratorij, with separate differential instruments, Nos. 1. 2, and 3 or No. i 

with NOB. 5, C, and 7; and for a fxed ohtervalory, Nos. 1 and 2, or No. 4 and 

Nos. 7, 8, and 9. The prices uf the different instruments include the spare and 

additional apparal us mentioned in the specifications, with the exception of the outer 

cases for the observ.itory diiTerential instruments. 

t The PortaHe Declinometer may lie constructed al a less expense, omitting the 

second magnet and ihe apparatus for experiments of deflection. 

: The cost of the Portable Unifilar, or of the Theo.lolite Magnetometer, will be 

increased by about 5/ otil., if the instrument is made available for obserrations both 

of inclination and horizonUl force, and by about V. or 21. if made available for only 

one of these purposes. 

I 

99 

Instruments made by Mr. Barrnw, 26, Oxenden-street, ffaymarhet-

£. !. d. 

25 0 0 

• . . . 15 15 0 

5-inch Prismatic Compass, with a compound bar 

card, ruby cap, stanti, &c., complete (the prism 

either direct or inverting) 

9|-inch Dip Circle 

6-inch ditto 

5 0 0 

A pair of Lloyd's intensity Needles for the 9J-inch 

circle . .. . 

Ditto for the 6-inch circle . 

Instruments mark by .Mr. George, Falmmith. 

Fox's Dip Circle and Intensity Apparatus, with 

spare jewels and an additional pair of deflectors . . . . . 20 2 0 

FIGURE 19.—Price list of instruments offered by Thomas Jones and Mr. Barrow of London and Mr. George 

of Falmouth, in 1844. (Printed in C.J.B. Riddell, Magnetical Instructions for the Use of Portable Instruments, 

London, 1844.) 

North American Research'' 

The discovery of the Americas more or less coincided 

with the first observations of variation/declination of the 

magnetic compass; indeed, Columbus is supposed to have 

observed variation during his initial voyage, and the observations that aroused Humboldt's interest in the subject were 

made in South America. In North America John Winthrop 

(d. 1779) collected observations that reportedly went back 

to 1672. 

Nathaniel Bowditch published observations as early as 

1815 and in 1829 the American Journal of Science printed 

contradictory articles on geomagnetism, by Bowditch and 

Simon de Witt. Th e field soon became as lively in the United 

States as in Europe. Hansteen had given one of his magnetometers to Sabine, who, replacing Hansteen's needle with 

one of his own, gave the apparatus to James Renwick, 

professor of natural philosophy at Columbia College. Renwick in turn sent it to Joseph Henry, at Albany, who 

exhibited it at the local Academy in 1830. Henry also made 

experiments on "dip" in 1830, apparently using an apparatus similar to that of the Royal Society. In 1834 a "dipping 

needle' made by Gambey "for the apparatus of the Military 

Academy" (West Point), was used for joint observations by 

Professor E.H. Courtenay of tTie Academy and Alexander 

Dallas Bache, an Academy graduate who was then teaching 

at the University of Pennsylvania. Bache was also using in 

1836 an instrument similar to Hansteen's design, which 

appears to have been "home made," as was another, consisting of a needle suspended in an evacuated glass jar, to 

test the effect of air resistance. 

During that decade a group of American scientists tried 
24 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

r-'V 

FIGURE 20.—Brooke photographic-recording magnetometer. Th e magnetometer is (in skeleton form) at the left, the recorder at the right. (From 

Philosophical Transactions of the Royal Society, volume 137, 1846.) 

to form a private association for a general magnetic survey 

of the United States. It evolved out of the individual efforts 

of Elias Loom is (first at Yale, then at Western Reserve 

College), John Locke (of Cincinnati), Bache, James Renwick, 

and a half-dozen others. Loomis circularized state surveyors 

and professors in an attempt to produce a chart of declination, reduced to the epoch of 1838. As for inclination, he 

noted that few American researchers had suitable dip circles. But Locke included that measurement in the results of 

his survey of the declination and dip in Ohio, the first 

survey west of the Alleghenies, having observed from 1838 

to 1845 with Robinson instruments and "Weber's improved 

transportable magnetometer,' which he obtained in London. His objective was to establish Cincinnati as the base 

point, linked to the new Toronto observatory. 

While at Yale, Loomis had measured declination with a 

Dollond theodolite that had an enlarged magnetic compass. 

When he moved to Western Reserve he added to his equipment a Gambey dip circle, for an expanded survey of Ohio 

and Michigan. From an analysis of his and Locke's results 

Loomis concluded that the dip circle was "one very ungreatful instrument," for even when they took all possible care— 

inverting and reversing the needle, using more than one 

needle, etc.—an error of 15.5 minutes of arc was found 

unavoidable. 

In 1836-1838 Bache, who had been made President of 
NUMBER 48 25 

the newly founded Girard College in Philadelphia, traveled 

to Europe for the college, making geomagnetic observations 

along the way (at 21 stations) using a dip circle by Robinson. 

It may have been at this time that Bache acquired the 

magnetometer by Gambey, which he used in 1840-1843 in 

his magnetic survey of Pennsylvania, and which is now in 

the Smithsonian (No. 2, Figure 32). 

Bache proposed in 1838 that Girard College construct a 

special iron-free building for use as a magnetic observatory, 

to incorporate instruments he had selected for the college 

during his European tour. His observatory magnetometer, 

made by Meyerstein, was another after the Gauss pattern, 

a unifilar instrument that was read by reflection and was 

part of the building itself. He also used Lloyd's vertical 

force magnetometer with a twelve-inch magnet made by 

Robinson. Bache donated another of these magnets to the 

Naval Department of Charts and Instruments in 1841 and 

cooperated extensively with observatories at Harvard and 

Toronto during the life of the Girard Observatory, which 

was closed in 1845. 

At Harvard, W.C. Bond and Joseph Lovering had used 

dip circles by Gambey and by Troughton and Simms, but 

like Loomis before him Lovering complained that even the 

best dip circles could vary by fifteen minutes of arc between 

instruments. By 1846 the Harvard dip circles were in the 

hands of Major J.D. Graham for his survey of the boundaries 

of the country, while the Cambridge observers, hoping for 

a more accurate indirect method, acquired the instruments 

recommended by the Royal Society to the British Colonial 

Observatories, including Lloyd's vertical force magnetometer. 

The Harvard instruments were acquired with the assistance of the Americal Academy of Arts and Sciences (Boston) 

and of the federal government, which also obtained instruments for the Military Academy and the "United States 

Exploring Expedition" (1838-1842) headed by Lt. Charles 

Wilkes. Ll. James Gilliss conducted simultaneous geomagnetic measurements in Washington at the Naval Depot, 

although he found himself limited to a declinometer resembling "an ordinary surveyor's compass," and a dip circle 

"rendered hors du combat from a bend of its pivots," both 

made in 1828. He replaced them in 1840 with a new 

declinometer designed by Gambey, but made by Simms, 

and a new dip circle apparently from the same maker. 

When Gilliss visited Europe in 1842-1843 to obtain 

books and instruments for the Depot, which was about to 

become the United States Naval Observatory, he was still 

seeking better instruments. He reported "a great diversity 

of opinion" respecting the most suitable dimensions for 

"magnetical" instruments, and declared that "it was with 

difficulty that I resolved to order any." 

Professor Gauss, at Gottingen, with 2.5 pound bars, was at one extreme; 

Dr. Lamont, at Munich, with needles 2/2 feet long, made of chronometer 

spring (probably a misprint or misstatement, referring to experiments by 

Lamont in using a chronometer spring to dampen the movement of the 

needle) and weighing about half an ounce, was at the other; whilst the 

committee of the Royal Society were intermediate. 

He finally decided "to copy the instruments made for the 

English observatories, differing from them only in points 

recommended by Professor Lloyd and Colonel Sabine." 

They were ordered from Henry Barrow, who succeeded 

Robinson after the death of the latter in 1841, and were 

made under the supervision of Sabine's assistant, Lt. Riddell, author of the aforementioned Magnetical Instructions. 

Like that used by Lefroy in Canada, Gilliss' apparatus varied 

slightly, both in the instruments actually used and in their 

dimensions, from Riddell's Instructions. 

In his book on the Girard College observations, Bache 

reported having replaced his Lloyd vertical force magnetometer with a similar instrument made by Joseph Saxton, 

a Philadelphia "mechanic' who was to become one of the 

most important, and certainly the most versatile, American 

instrument-maker of the nineteenth century. This apparently occurred during Bache's observations of 1840-1845, 

and it may have been the first really significant geomagnetic 

instrument of American construction. Apparently it no 

longer exists, nor does its principal rival for this honor, a 

dip circle made by another Philadelphia mechanic, Isaiah 

Lukens, in 1819. The earliest American-made instruments 

in the present collection are a dip circle (No. 31, Figure 61) 

by William Wurdemann of Washington that was in use by 

1863, and a magnetometer (No. 6, Figure 35) by William 

Grunow, a German immigrant who was active as an instrument-maker in New York City from 1861. 

In 1844 Bache became head of the U.S. Coast Survey, 

and two years later the Smithsonian Institution opened its 

doors, with Joseph Henry as its first head (Secretary). With 

two enthusiasts in strategic positions, Washington not surprisingly emerged as a center of geomagnetic research. Th e 

Coast Survey had been founded in 1816, under the direction of F.R. Hassler, a Swiss immigrant scientist. Hassler 

was soon in conflict with the Congress over appropriations, 

particularly the cost of instruments; but they had nothing 

to complain of with regard to his magnetic work, which 

appears to have been little more than a magnetic reconnaissance of Connecticut and New York in 1833, made with an 

ordinary "azimuth compass." By the time Bache succeeded 

Hassler, on the death of the latter in 1843, the activity of 

the Coast Survey had been largely restricted to conventional 

geodetic surveying. However, the practice of taking observations was resumed by Bache and became increasingly 

important during his 24-year tenure as Superintendent. 

Measurement of declination, dip, and absolute horizontal 

intensity, with "a set of Riddell's portable magnetic instruments," made by (Thomas?) Jones of London, and a dip 

circle by "Patton' of Washington, is mentioned in 1844. 
26 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

T h e same instruments are mentioned in successive years, 

although Patton's dip circle seems to have been supplanted 

by one of Barrow's. By 1849 the Survey had begun to 

number its instruments, dip circle no. 1 being a Jones 

instrument, perhaps from the "set" just mentioned. Also 

mentioned are dip circles by Gambey (with a ten-inch 

needle) and one or more others by Barrow (the Survey's 

no. 9, a Barrow instrument with a six-inch needle, is in the 

present collection [No. 30, Figure 60]). Th e Survey Report 

for 1847 mentions a magnetometer, described as "Weber 

and Riddell's portable declinometer," and that for 1851 

refers to "a portable declinometer of Gauss and Weber as 

arranged by Professor Lloyd and Colonel Sabine, and made 

by Jones." 

A "Table of Magnetic Results,' published by the Survey 

in its Report for 1881, lists observations dating from the 

1830s and gives some indication of the instruments used. 

Most of the Survey's early observations were made with 

instruments borrowed from other sources, notably the 

Smithsonian and the Naval Observatory. A Barrow dip 

circle no. 4 is mentioned in use in various locations into the 

1870s (it was used in Central Park, New York City, in 

1872). Th e aformentioned Wurdemann dip circle was still 

in use in 1881, when it was carried down the west coast, 

from Sitka to San Diego. 

Smithsonian interest in a "magnetic survey" was mentioned as early as its second Annual Report (1848), when 

Joseph Henry visited Lefroy at his Toronto observatory. 

Henry subsequently ordered a set of magnetic instruments 

from London. It was the first of several sets, for the Smithsonian became the source of instruments used on expeditions. When Lt. Gilliss set sail for his Chilean solar parallax 

expedition of 1849 he had a set of magnetic instruments 

purchased for him by the Smithsonian (which was paid for 

by a special Congressional grant). Another set had been 

received by 1851 and was lent to (now) Colonel Graham 

for use on the Mexican Boundary survey. By 1853 the 

Smithsonian had four sets, another of which was lent to Dr. 

Kane for the Grinnell expedition to the Arctic. Kane returned these in 1856 and they were lent to Baron Muller 

for use in Mexico and Central America, where, according 

to Henry (but probably erroneously) no observations had 

been made since Humboldt. Subsequent reports note Muller's long silence and finally the loss of the instruments, 

"captured and destroyed by robbers." They also identify 

the set, a small theodolite, a declinometer, a unifilar magnetometer made by Jones, and a Barrow dip circle. 

T h e Smithsonian also had its own observatory, a specially 

constructed underground room that in 1853 was supplied 

with at least part of a set of the photographic recording 

instruments devised by Brooke, consisting of a declinometer 

(a steel bar supported by "several" silk threads), a bifilar 

intensity instrument, and an inclinometer supported on 

knife edges (probably Lloyd's vertical force magnetometer) 

(see Figures 21 and 22). Th e Report for 1860 mentions the 

receipt of the "remaining" Brooke instruments; but it also 

reports the conclusion that the observations in Washington 

were nearly the same as those in Toronto and Philadelphia. 

Henry, who lacked the empire-building instinct, dispatched 

the instruments (except for one) to a more appropriate site. 

Key West, Florida. 

T h e Smithsonian observatory had been a joint venture 

of the Institution and the Coast Survey, and so was the one 

at Key West. However, the Smithsonian was leaving the 

field of geomagnetic research. Its instruments were apparently transferred to the Coast Survey, for when LI. Hayes 

made an expedition to "the arctic seas" in 1860 he borrowed 

instruments from the Coast Survey, a magnetometer by W. 

R. Jones and the aforementioned Patton dip circle, which 

had been improved by new needles by William Wurdemann, 

now an employee of the Survey. 

In the Report for 1857 Bache listed 160 "magnetic stations" at which observations had been made. Lines of equal 

declination (isogonic lines) had been mapped for the coastline by 1855 and were to be extended by 1875 to the whole 

country. Th e most imposing instrument remained the 

Brooke magnetograph, which was moved from Key West 

to Madison, Wisconsin, in 1876. In 1882 the Coast Survey 

acquired an improved magnetograph, an example of the 

instrument designed shortly before by Patrick Adie for the 

Kew Observatory (see Figure 23). Th e instrument was 

installed at its new observatory in Los Angeles, where its 

bulk and marble pillars (see Figure 36) were reminiscent of 

Duhamel's "sculpture garden" of a century earlier. 

A "Quiescent Period"?^ 

T he movement for the establishment of "permanent" 

observatories seems to have declined, after peaking in 1841, 

when twelve were inaugurated. Only two were set up in 

1842 and few others during the next generation. Th e fervor 

that had attended the founding of Gauss' Magnetische 

Verein and of the British Colonial Observatories died away, 

as did, in the course of time, their promoters, Weber, 

Lamont, Lloyd, and Sabine. They were not to be succeeded 

by enthusiasts of equal influence. 

This has been seen as the beginning of a quiescent period 

in the study of terrestrial magnetism, lasting until about 

1900. Ther e is, however, plenty of evidence to the contrary. 

Observation did not slacken after the 1840s; in fact, it 

proliferated. On the one hand differences in geomagnetic 

direction and force from place to place made the subject an 

adjunct to the geodetic survey. On the other hand, diurnal 

and secular variation made evident the similarity between 

geomagnetism and that other recalcitrant science, meteorology, and numerous meteorological observatories became 

also magnetic observatories. Thus geomagnetism was in a 

sense absorbed by related and more venerable fields. 
NUMBER 48 27 

FIGURE 21.—Plan of the magnetic room of the Smithsonian Institution, 1860, showing the locations of the 

declination magnet (D), horizontal force magnet (H), and vertical force magnet (V). Th e "b's" are gas 

lamps, the "r's" photographic recording cylinders. Th e distances from the reflecting mirrors to the recording 

cylinders is 9 ft, 6 in/2.9 meters. (From Smithsonian Institution Annual Report for 1860.) 

T h e Brooke magnetometer was moved to Key West in 1860, the first of several moves. According to 

the Coast Survey Report for 1884 it was still in use, at Point Barrow, Alaska. 

It is to this supposedly quiescent period that most of the 

older instruments in the present collection belong. The 

Coast Survey instruments appear to have been long-lived 

and widely used. Its instrument department was mainly 

involved in their repair or modification—a circumstance 

that raises the question of the resemblance of the extant 

instruments to their original forms. (In 1883 the Survey 

participated in an International Polar Expedition with a 

magnetometer "hastily constructed from some remains of 

an earlier instrument".) American geomagnetic equipment 

continued to be primarily of English origin, although in the 

1880s the Survey acquired and tried out instruments of the 

French and German magnetic surveys. These instruments 

survive, in part, certainly, because they failed to satisfy the 

notions of the Americans as to what an instrument should 

be. These instruments do seem to betray their national 

origins, the French being jewel-like in their elegance and 

diminutive size, and the German instruments being marvels 

of complexity and bulk. It was claimed that the German 

instruments were "portable," but the Americans almost 

invariably used them in fixed observatories. 

T he Coast Survey showed a decided preference for the 

instruments of the "Kew (Observatory) type,' as made by 

the firm of Dover. But American-made instruments did 

exist, as has been noted. Another special Congressional 

appropriation, this one for observations in connection with 
28 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 22.—Instrutnents in the Sinithsonian magnetic room. Right: "Vertical force instrument or balanced magnetometer.' Above: bifilar magnetometer, "after Gauss' design." Note the 90° twist in the two suspension 

fibres. (From Smithsonian Institution Annual Report for 1860.) 

the transit of Venus on 8 December 1874, included funds 

for a dip circle that survives in the collection (No. 32) and 

was apparently made by the shop of the Naval Observatory. 

Finally, in the late 1870s the Coast Survey ventured into 

the design of its own instruments, "with a special view of 

making them more portable than the older instruments, 

which were found unnecessarily large and heavy." From 

this time it is possible to speak of a typical Coast Survey 

instrument (see Figures 24-27, and No. 11, Figure 39). 

A new era of international scientific cooperation also 

began at this time. For example, the transit of Venus just 

mentioned saw the establishment by the United States and 

Britain of temporary observatories around the Pacific. Geomagnetism was only a secondary objective in this case, but 

for the first International Polar Year (1881-1882) thirteen 

circumpolar observatories were set up explicitly for geomagnetism, by Denmark, Germany, France, Britain, Finland, and the United States. 

T he result was hardly commensurate with the objective 

because the effort was hastily organized. Most stations were 

ill-equipped, and many began their observations late or 

omitted some of the required measurements. Only the 

French had self-registering instruments. Worst of all was 

the failure of the supporting nations to supply funds for the 

analysis of the observations, an undertaking that lacked the 

romance and national prestige attached to expeditions. 

Nevertheless, there were published results, which occupy 

about five feet of shelf-space, and have proven to be important for the study of electrical effects in the Polar atmosphere during the aurora and of the propagation of magnetic 

disturbances. This international venture prepared the way 

for improved expeditionary research in the 1890s. 

Kew Observatory remained doggedly vigilant in maintaining standards for instruments. Its staff, between 1853 

and 1897, tested and calibrated 21 magnetographs, 117 

unifilar magnetometers, 155 dip circles, and a number of 

collimating magnet tubes and dip needles. It also trained 

observers and continuously monitored the magnetic elements, as a basis for measurements elsewhere in Britain. 

Lastly, it allowed scientists from the continent and the 
NUMBER 48 29 

FIGURE 23.—Adie magnetograph. This photo-recording instrument, first described in 1859, was designed 

by J. Welsh at Kew Observatory and made by the London instrument-maker, Patrick Adie. It is similar, 

with improvements relating primarily to the photographic registration, to the Brooke magnetograph 

acquired by the Smithsonian in 1853. Th e latter no longer exists, but the present collection includes an 

Adie magnetograph acquired by the Coast Survey in 1882 (No. 8, Figure 36). 

Thre e magnetic sensing elements, for changes in declination and in both components of magnetic force, 

rest on individual 15'/2-in/39.4-cm square marble plates. Th e octagonal box is the photo-register. (From J. 

E.H. Gordon, A Physical Treatise on Electricity and Magnetism, New York, 1880.) 

United States to compare their own instruments with British 

standards, thereby increasing the values of surveys generally. 

The United States Coast Survey became the Coast and 

Geodetic Survey in 1878, thus obtaining formal sanction 

for magnetic work in the interior of the country. In the 

same year, the state of Missouri began the first comprehensive state (although it was privately financed) magnetic 

survey since the 1830s. Surveys were also sponsored by the 

National Academy of Sciences (1871-1876), by the United 

States Lake Survey, and by the army, in the Indian Territories. 

The geodesists' determination to realize a systematic survey of the earth was achieved by deferring consideration of 

a number of puzzling side effects. Ther e was the effect of 

the aurora borealis on terrestrial magnetism, which had 

been given a scientific basis by S.H. Christie in 1831, and 

the erratic behavior of instruments during "magnetic 

storms," which had been noticed in 1834. In the 1840s 

Lamont had found that declination changed in a ten or 

eleven year cycle, and that this had some degree of correspondence to a recently discovered cycle in the frequency 

of occurrence of sunspots. In 1851 Sabine claimed that the 

daily magnetic changes were really composed of two different changes, one within the earth, the other outside of it. 

In 1861 Lloyd demonstrated the existence of electric currents, and hence magnetic currents, in the earth's crust. 

These accumulated peculiarities provided material for 

study by the permanent observatories, which turned, during 

this "quiescent period," to the systematic recording of periodic and unusual magnetic phenomena. For this the photographic recording technique was ideal, but the conventional declinometers and inclinometers to which it was originally applied were not. Sensitivity to change, not extreme 

accuracy, was the primary consideration. The sensing instruments were accordingly redesigned, usually into sets of 

three, for declination, horizontal force, and vertical force. 

In recognition of their special purpose and relative charac-
30 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 24.—Dip circle represented as "typical" in the Report of the Coast Survey for 1875. In the present 

collection it is exemplified by No. 30 (Figure 60). 
NUMBER 48 31 

FIGURE 25.—Magnetometer, with theodolite, of a type used by the Coast Survey as illustrated in its Report 

for 1881, and described as "Weber's design." It is not represented in the present collection. 
32 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 26.—Magnetometer, also illustrated in the Coast Survey Report for 1881, and described as 

"Lamont's design." 
NUMBER 48 33 

MAGNETOMETER 

AND 

AI.TAZIMUTH INSTRUMENT 

FIGURE 27.—Magnetometer and "altazimuth instrument" (theodolite) used by the Coast Survey in 1894, 

as illustrated in its Report for that year. No. 11 (Figure 39) in the present collection is an instrument of this 

type. 
34 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

No. 1. 

ISOGONIC MAP o f th e UNITED STATES fa r th e yea r 1888. 

C A fr 3 w>^-<VK«» 

ISOCLINI C MAP of th e UNITED STATES fo r th e yea r 1888. 

CfcUAurvcycMlr*. 

ISODYNAMIC MAP of the UNITED STATES for tho year 1888. 

No. 4. 

ISODYNAMIC MAP of the UNITED STATES fo r the year 1688. 

FIGURE 28.—These charts show, for the United States in 1888, (1) lines of equal declination (isogonic lines, 

or magnetic longitude), (2) lines of equal inclination (isoclinic lines, or magnetic latitude). Whereas the 

network of latitude and longitude lines is sufficient to the solution of problems of geography, the network, 

such as it is, of isogonic and isoclinic lines merely indicates that terrestrial magnetism is a more complex 

problem. Points of equal magnetic intensity can also be diagrammed, the result being (3 and 4), networks 

of "isodynamic" lines. (From Short Description of Articles Forming the Coast and Geodetic Survey Exhibit at the 

Centennial Exposition of the Ohio Valley and Central States, Washington, 1888.) 

ter (they had to be recalibrated frequently) they were endowed with a different name, "variometer." 

These observations answered some questions and raised 

others. In the 1880s the existence of vertical electric currents in the atmosphere was demonstrated by Adolph 

Schmidt of Gotha and Arthur Schuster of England. In his 

development of Gauss's mathematical treatment of geomagnetism, Schuster was led to two further conclusions; 

first, that most of the earth's magnetism arises in events 

below the surface, partly caused by increased conductivity 

at greater depths; second, that diurnal and secular (i.e., 

daily and long term) variations are due to electromagnetic 

interaction between the earth and its atmosphere. In 1897 

L.A. Bauer published summary conclusions of the halfcentury of geomagnetic theorizing since Gauss: about 95% 

of the earth's magnetic field is due to causes within the 

crust. Another 2.5% is due to causes outside the crust. A 

final 2.5% cannot be described as an intrinsic magnetic 

field, but indicates vertical currents of atmospheric electricity. 

T h e physical explanation of these broad conclusions was 

far from complete, and the fundamentals of terrestrial 

magnetism remained elusive. Th e numbe r of other phenomena to which it was connected continued to increase. 

Not only was its relationship to solar phenomena found to 

be ever more complicated, but in 1894 E.L. Leyst claimed 

that geomagnetism is influenced by the planets, and two 

years later R. von Eotvos discovered a relationship between 
NUMBER 48 35 

FIGURE 29.—The Kew magnetometer. This instrument, shown at the left 

arranged for "vibrations" (i.e., intensity measurement), and below arranged 

for deflection, was designed at Kew and introduced before 1880. Th e 

instrument is represented in the present collection by No. 9 (Figure 37). 

(From J. E. H. Gordon, A Physical Treatise on Electricity and Magnetism, New 

York, 1880.) 
36 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 30.—Photographic registration at the magnetic station of Pare Saint-Maur Observatory, France, in 

the 1880s. (From La A/a/wrf, 11, 1882-1883.) 

geomagnetism and gravity. "The earth seems," wrote A. W. 

Rucker in 1896, "alive with magnetic forces, be they due 

to electric currents or to variations in the state of magnetized matter." 

A Meteorological Congress was held in Chicago in 1893, 

in connection with the World Columbian Exposition. This 

meeting included the first international discussion since 

1880 of the results of recent geomagnetic studies, for which 

a new generation of well-trained physicists, and instruments 

developed as by-products of the burgeoning electrical technology, provided new approaches and points of view. 

Early Twentieth Century Research^ 

In 1896 the first specialized journal, Terrestrial Magnetism 

and Atmospheric Electricity, was begun. In 1899 the Coast 

and Geodetic Survey created a Division of Terrestrial Magnetism, and an International Magnetic Congress convened, 

to plan a new level of commitment. Most importantly, in 

1904 a Department of Terrestrial Magnetism (usually abbreviated DTM) was established in the two-year-old Carnegie Institution of Washington. 

T h e key figure in the United States was L.A. Bauer 

(1865-1932), a civil engineer who had been employed by 

the Coast Survey from 1887. Adopting geomagnetism as 

his major field, Bauer studied in Berlin, where he received 

a doctorate in 1895. He subsequently worked with the 

Maryland State Geological Survey and completed, between 

1896 and 1899, the first American geomagnetic survey 

equal in the quality of its results to the British surveys. As 

head of the Coast Survey's new Division of Terrestrial 

Magnetism, Bauer initiated a new survey of the entire 

country, which by its completion in 1915, had "occupied" 

5500 stations (compared to about 160 stations between 

1844 and 1856). Key stations were regularly reoccupied, to 

obtain secular variation data. Commenting on the support 

he had received for these projects, Bauer remarked, "never 
NUMBER 48 37 

before has such enthusiastic interest been taken in this 

elusive subject." 

In 1904 Bauer became the first Director of the Carnegie's 

DTM. Like other divisions of the Carnegie Institution, 

explicitly focusing on international (and hitherto neglected) 

subjects, the DTM began a World Magnetic Survey, with 

cruises of its ships, the Galilee, in the Pacific Ocean, 1905-

1908, and Carnegie (a "non-magnetic" ship), 1909-1929. 

The Carnegie made seven cruises, including several circumnavigations, while the DTM at the same time dispatched 

land expeditions to Alaska and the Canadian Arctic, South 

America, Africa, and Asia. 

This extraordinary activity required an accelerated program for the improvement of instruments, an effort that 

had already begun at the Coast Survey and was continued 

in the instrument shop of the DTM. Older Coast Survey 

instruments were tested, as were the Survey's English, 

French, and German instruments. Th e present collection 

includes (No. 14, Figure 43) the first DTM magnetometer, 

which followed the Coast Survey's standard theodolitemagnetometers of 1894 (Figure 27) in featuring octagonal 

collimator magnets, to facilitate inversion; a second generation reverted to cylindrical magnets, the octagonal having 

been found magnetically irregular. These (see No. 15, 

Figure 44) were designed by DTM and manufactured by 

Bausch, Lomb, and SaegmuUer, an amalgamation (1905) of 

instrument-makers in Washington and in Rochester, New 

York. 

Because of their bulk, these early DTM magnetometers 

were inappropriate for field work in remote areas. For this 

application the size was reduced and then two new "universal" magnetometers were designed. One type (Nos. 17 and 

18, Figures 46 and 47) incorporated magnetometer, theodolite, and dip circle into a single unit, eliminating the 

need to carry two separate instruments. The second type 

(No. 19, Figure 48) comprised a theodolite-magnetometer, 

an earth inductor, and a portable sine-galvanometer. These 

were separate pieces, hence it was not, strictly speaking, 

"universal." However, it was more significant in its replacement of the dip circle by the earth inductor. 

The earth inductor, an instrument for measuring the 

electric effect resulting from the rotation of a coil of wire 

in the earth's magnetic field, had been introduced by Weber 

in 1837. That the electric current generated by such an 

instrument is proportional to the direction and intensity of 

the local magnetic field was obvious enough. However, the 

instrument (particularly its galvanometer) was inadequate 

for the precise measurement of this current—to the degree 

that it existed through most of the nineteenth century only 

as a demonstration device for classroom use (see Figure 72). 

This weakness was largely rectified by Wild and Mascart in 

the 1880s, by their perfection of a "null method," that is, a 

method in which the galvanometer merely indicates the flow 

of current, but does not measure it. Still, the earth inductor 

remained so inferior to the dip circle, for geomagnetic field 

work, that it was scarcely used, indeed, scarcely thought of, 

even after further improvement of the galvanometer had 

justified its reconsideration. This reconsideration at the 

DTM, 1910-1915, yielded an instrument that was more 

reliable than the dip circle. 

T he DTM encountered its most difficult challenge in 

instrument design in meeting its commitment to a world 

ocean survey, for the accuracy of instruments used at sea 

lagged far behind that of those used on land. Between 1905 

and 1913 two instruments for measuring declination and 

horizontal intensity, and two others for inclination, were 

designed and installed on the Galilee and the Carnegie. Only 

one of these types is extant, the Lloyd-Creak dip circle (No. 

37, Figure 65). As the name indicates, it was not, strictly 

speaking, a DTM design. The original models were built in 

England, according to specifications of E.T. Creak of the 

Admiralty Compass Division. When tested on Coast Survey 

vessels in 1904-1905, they failed. Bauer gave the British 

maker new specifications and further modified the circles 

later in the DTM instrument shop. The result was to bring 

the quality of sea dip measurements almost up to that of 

land measurements. Ultimately the DTM produced dip 

instruments that agreed within a half-minute of arc. 

Bauer specified four principles of instrument design. First 

was "to have instruments, methods of observation, and 

methods of computation all form one harmonious whole 

. . " This reflects his concern that the data be reduced 

easily and published quickly. The second was to join several 

functions in one instrument. An immediate reason for this 

was to lighten the work of the observer; a deeper reason 

was to provide for checking one instrument against another. 

Variable conditions in the field dictated, thirdly, that any 

device be versatile. It had to work in high and low intensities, high and low dip, and high and low declination. The 

last requirement was called "symmetry;" all of the magnetic 

elements were to be equally emphasized. 

The Carnegie Institution's instrument program was designed to meet these specifications, and largely succeeded. 

So did its program of geomagnetic exploration. Having 

accomplished much of its mission, the Carnegie Institution 

(whose ship Carnegie had its geomagnetic voyages ended by 

an accidental fire in 1929), reduced its activities, and finally 

withdrew from the field in 1946. The Coast Survey similarly 

reduced its activity. 

In part these reductions in activity were offset by the 

entry into the field of geomagnetic research of the wellendowed laboratories of the mineral companies. That a 

magnetic compass responds to the nearby presence of iron 

ores had been known virtually since the compass itself was 

known, and the cheap and handy miner's dip needle had 

been a familiar sight for centuries (see Figure 68). What 

was new in the twentieth century was an awareness that the 

presence of many kinds of mineral—including petroleum— 
38 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

modifies the magnetic properties of the earth in its vicinity. 

This in turn led to the development of magnetometers that 

were both scientifically respectable and useful for mineral 

prospecting. 

Adolf Schmidt, who had been a leader in magnetic studies 

since the 1880s and was Director of the Prussian Meteorological and Magnetic Observatory from 1927, introduced 

in 1915 a new instrument, a "magnetic vertical balance," 

which was a refinement of the venerable vertical force 

magnetometer of Lloyd, and which was to revolutionize 

mineral prospecting by magnetic methods. Schmidt's instrument was adopted for mineral exploration in the United 

States in the 1920s. Its improvement was taken up at the 

Gulf Research and Development Corp., of Pittsburgh, 

which made the example in the present collection (No. 22, 

shown herein only as a diagram. Figure 51). It is particularly 

sensitive to local geomagnetic anomalies, and hence has the 

characteristics of a variometer. 

More recently the variometer itself has been adapted for 

use both in the geomagnetic observatory and in mineral 

prospecting. This is exemplified in the present collection by 

No. 25 (Figure 55), an instrument made by the Ruska 

Instrument Company of Houston, Texas. Here the variometers are "surrounded" by an artificial magnetic field created by a steady current in a Helmholz coil around the 

instrument. It had long been thought that the intervention, 

between the magnet and the terrestrial field, of such a 

steady magnetic field would improve the sensitivity of the 

instrument, but not until the twentieth century was it possible to produce a field of the requisite constancy. Advances 

in electrical technology made it possible. 

T h e advent of aircraft created the possibility of another 

improvement, the rapid geomagnetic survey of large areas, 

in search of magnetic anomalies meriting closer scrutiny. 

Research on the development of a suitable magnetometer, 

undertaken at Gulf Research and Development, led to the 

construction of an experimental instrument in 1940 (No. 

26, Figure 57). As in the Ruska instrument just mentioned, 

the sensing element, devised by Victor V. Vacquier, was 

located within a steady artificial magnetic field, but the 

principle of the instrument was different. Th e sensing element was free of mechanical parts, depending on the measurement of "saturation effects." 

In terms of sensitivity the Gulf airborne magnetometer 

was said to be as superior to the Schmidt magnetometer as 

the latter was to the ordinary dip circle. However, the 

airborne device, which was towed behind the aircraft in a 

torpedo-shaped housing, was still influenced by the vibrations of the plane. Further experimentation was interrupted 

by the Second World War, which, however, gave occasion 

for improvement in a new direction. It was suggested that 

it might be capable of responding to the presence, beneath 

the sea, of an iron body with the bulk of a submarine. Tests 

were sufficiently promising to justify a program, centered 

at the United States Naval Ordnance Laboratory, for further development. Th e collection includes (No. 27, Figure 

58) the second version of the result, dated about 1953. 

Called MAD (Magnetic Airborne Detector), it is a complex 

of electronic components, entirely located within the aircraft, that continuously record the total intensity of the field 

and the magnitudes of directional angles. 

By the time of the International Geophysical Year of 

1957-1958, airborne magnetometers had been joined by 

satellite magnetometers. Formally, American geomagnetic 

research is now divided between the United States Geological Survey and the National Ocean Survey (of which the 

old Coast Survey is a unit). Th e subject has broadened 

greatly both in terms of the questions asked and in the 

methods used. Th e grand and heroic era of geomagnetic 

expeditions may be over, but the subject, if less romantic, 

has achieved a higher level of respectability. Th e search for 

minerals by geomagnetic means is even more urgently pursued—and more scientifically. Popular interest in the theory of continental drift has given the science of geomagnetism unprecedented "visibility," in the search for the magnetic orientations of undersea geological formations, such 

as the successive strata either side of the mid-Atlantic ridge, 

a study called paleomagnetism. In short, scientists still seek, 

on a larger canvas, the mechanism that produces the earth's 

magnetism. 
Catalog of Geomagnetic Instruments 

Collection 

no. 

1 

2 

3 

4 

5 

6 

Figure 

no. 

31 

32 

33 

34 

— 

35 

Type 

Declinometer 

Variation 

transit 

Magnetometer 

Unifilar magnetometer 

Unifilar magnetometer 

This instrument is sim 

telescope is missing. 

Magnetometer 

Identification 

Gambey type 

Gambey-Bache; mkd. 

Gambey a Paris 

type of Lamont 

mkd. Griffin 8c George, 

London 

unmarked 

ilar to that illustrated in the Deluil 

Grunow; unmarked 

Date 

ca. 1830 

ca. 1840 

19th cent. 

1962 

mid-19th cent. 

catalog of 1863 (see Figure 

ca. 1870 

Source; 

NMAH catalog no. 

Purchase 

82.688.1 

Carnegie Inst. 

316592 

Univ. of Virginia 

323355 

Purchase 

321545 

Univ. of Virginia 

336624 

: 13, no. 510). Th e 

U.S. Military 

Academy 

316428 

Unifilar mag- mkd. Otto Fennel ca. 1875 USC&GS 

netometer 316512 

T h e Fennel magnetometers, primarily intended for use in mines, were more durable and portable than 

research instruments. This small (14'/2 inch high) instrument has a massive copper damping plate surrounding the magnet to facilitate quick reading. Th e instrument is incomplete. 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

36 

37 

38,6 4 

39 

41 

42 

43 

44 

45 

46 

47 

48 

Magnetograph 

Magnetometer 

Magnetometer 

Magnetometer 

Magnetometer 

Magnetometer 

Magnetometer 

Magnetometer 

Magnetometer 

Universal 

magnetometer 

Universal 

magnetometer 

Magnetometer 

and earth inductor 

Adie 

Kew type; mkd. 

145 

Dover 

French survey type; 

mkd. Chasselon 

42;CS2 1 

Coast Survey; m 

18 

a Paris 

ikd. CS 

Eschenhagen-Tesdorpf; 

mkd. CS 25 

Wild-Edelmann; 

CS2 2 

CIW 1 

CIW 4 

CIW 8 

CIW 19 

CIW 21 

CIW 26 

; mkd. 

ca. 1880 

1880 

ca. 1884 

1892-1893 

ca. 1900 

1902 

ca. 1902 

ca. 1905 

1906 

1911 

1911 

ca. 1913 

USC&GS 

316525 

USC&GS 

316506 

USC&GS 

316507 

USC&GS 

82.671.8 

USC&GS 

316505 

USC&GS 

316518 

Carnegie Inst, 

83.39.04 

Carnegie Inst 

316516 

U.S.G.S. 

82.671.11 

U.S.G.S. 

82.671.3 

USC&GS 

316504 

USC&GS 

320627 

39 
40 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Collection 

no. 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

Figure 

no. 

— 

50 

51 

52 

53 

55 

57 

58 

59 

— 

Type 

Magnetometer 

and earth inductor 

This apparatus, tecl 

Magnetometer 

Magnetometer 

Variometers 

Variometers 

Variometers 

Airborne magnetometer 

Airborne magnetometer 

Demonstration 

Geodetic 

Identification 

CIW 28 

inically similar to No. 19, Figure 48, 

British India survey 

pattern; mkd. CS 40 

Schmidt; mkd. Gulf 

Research & Development Co, Pittsburgh, 

Pa. 

Edelmann; mkd. Dr. T. 

Edelmann, Miinchen 

Eschenhagen-Topfer; 

mkd. Otto Toepfer 

Potsdam 

Ruska; mkd. Ruska Instrument Corp., Houston, Texas 

Gulf; mkd. made by 

Gulf Research & Development Co., Pittsburgh, Pa. 

mkd. U.S. Naval Hydrographic Office. 

VAM 

INCLINOMETERS (dip circles) 

U. Vt.; unmarked 

Froment; mkd. Froment a Paris 

Date 

ca. 1916 

was used by CIW in 

ca. 1927 

20th cent. 

ca. 1890 

ca. 1900 

ca. 1950 

ca. 1940 

ca. 1953 

early 19th 

cent. 

ca. 1860 

Source; 

NMAH catalog no. 

U.S.G.S. 

82.671.7 

South America in 1917-1919. 

U.S.G.S. 

82.671.2 

Gulf Research 

& Development 

MHIP8745 

USC&GS 

83.39.5&6 

U.S.G.S. 

82.671.12 

U.S.G.S. 

82.671.13 

Gulf Research 

& Development 

MHIP8745 

U.S. Naval 

Oceanographic 

Office, Bay 

St. Louis, Mich. 

81.607.1-13 

Univ. of Vermont 

326995 

U.S. Naval Observatory 

327705 

33 63 

In size and general appearance the instrument resembles No. 30 (Figure 61). The 10-in/25.4-cm circle is 

graduated to ten minutes of arc, but without reading lenses. The needle is missing. P.G. Froment lived from 

1815 to 1865. 

30 

31 

32 

60 

61 

— 

Geodetic 

Geodetic 

Geodetic 

Barrow; mkd. CS 9 

Wurdemann; mkd. CS 

10 

U.S. Naval Observatory 

ca. 1860 

ca. 1860 

1874 

USC&GS 

307207 

USC&GS 

314633 

U.S. Naval Observatory 

327714 

A simple instrument with a 6-in/15-cm needle and a scale marked to read only in minutes. Nonetheless a 

note attached identifies it as the product of a special congressional appropriation on the occasion of the 

transit of Venue of 8 December 1874, and it was exhibited at the Philadelphia International Exposition on 

1876. ^ 

Geodetic Kew type; mkd. CS 23 ca. 1880 U.S. Naval Observatory 

314632 
NUMBER 48 

Collection 

no. 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

Figure 

no. 

62 

61,6 4 

63 

65 

60 

— 

63 

67 

68 

68 

68 

69 

69 

Type 

Geodetic 

Geodetic 

Geodetic 

Geodetic 

Geodetic 

Geodetic 

Geodetic 

Prospecting 

Prospecting 

Prospecting 

Prospecting 

Prospecting 

Demonstration 

Identification 

Kew type; mkd. Dover 

85 

French survey type; 

mkd. Chasselon a Paris 

No. 40. CS 24 

Kew type; mkd. Dover 

158 

Lloyd-Creak; mkd. 

Dover 168 

Lloyd-Creak; mkd. 

Dover 169 

Kew type; mkd. Dover 

174 

Kew type; mkd. Dover 

240 

Hotchkiss; "Superdip" 

mkd. W & LE Gurley 

mkd. Dietzgen 

mkd. Keuffel & Essor 

unmarked 

mkd. Queen, Philadelphia 

Date 

ca. 1880 

ca. 1884 

ca. 1918 

ca. 1900 

ca. 1900 

ca. 1900 

ca. 1890 

1929 

ca. 1890 

ca. 1900 

20th cent. 

ca. 1912 

41 

Source; 

NMAH catalog no. 

U.S. Naval Observatory 

327706 

USC&GS 

316508 

Carnegie Inst. 

83.39.2 

U.S.G.S. 

316509 

U.S.G.S. 

83.39.3 

U.S.G.S. 

82.671.4 

Carnegie Inst. 

83.39.1 

W. Hotchkiss 

81.0488 

Purchase 

335530 

S.H. Oliver 

314642 

Batchelor Foundation 

319047 

MHIP8740 

U.S. Dept. of Interior 

261270 

47 

48 

49 

50 

51 

52 

53 

70 

71 

72 

72 

72 

Marine 

Observatory 

Demonstration 

Demonstration 

Demonstration 

Demonstration 

Demonstration 

EARTH INDUCTORS 

CIW 3 

mkd. CS 8 

mkd. Jas. W. Queen, 

maker, Phila. 

I0.75-in/27-cmcoil 

mkd. Max Kohl, Chemnitz. Central Scientific 

Co., Chicago 

11.8-in/30-cmcoil 

unmarked 

6.25-in/16-cm coil 

Hawkins & Wale 

I8-in/46-cm coil 

unmarked 

coil diam. 

9.5-in/14-cm 

1912 

ca. 1950 

20th cent. 

20th cent. 

mid-19th cent. 

1870s 

early 20th 

cent. 

U.S.G.S. 

82.671.5 

U.S.G.S. 

82.671.1 

Franklin College 

337246 

Trinity College 

81.743.4 

Princeton Univ. 

318589 

U.S. Military 

Academy 

322994 

Wabash College 

322994 
42 

SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Collection 

no. 

54 

55 

56 

Figure 

no. 

73 

74 

75 

Type 

Induction apparatus 

Induction apparatus 

Terrestrial 

magnetic plot 

(model) 

Identification 

MISCELLANEOUS 

Lamont type; mkd. CS 

1 

Nelson; mkd CS M 

Bache; See Figure 5 for 

marking 

Date 

20th cent. 

20th cent. 

1862 

Source; 

NMAH catalog no. 

U.S.G.S. 

82.671.10 

U.S.G.S. 

82.671.9 

unk. 

314745 
Notes 

' A.C. Mitchell's astonishingly detailed "Chapters in the History of Terrestrial Magnetism," which ends with the year 1500, is in sharp contrast to the 

sparse historical literature on the subject in subsequent times, where we are 

limited to such sketchy treatment of the 17th and 18th centuries as found 

in Mottelay's Bibliography and the "Historical notes" to the Geomagnetism of 

Sydney Chapman and Julius Bartels. Button's Traite de I'aimant of ihe 1780s 

is perhaps the first "modern" book on the subject. (Full citation of these 

works will be found in the bibliography.) 

" Although limited in its objective, Anita McConnell's book on early instruments seems to be the only predecessor to our catalog. Th e instruments 

used at the Royal Society were described by Cavendish and Gilpin. Arago's 

extended article on "Magnetism terrestre" gives an interesting picture of 

early instruments and observations in France. Th e publications of Gauss, 

Weber, and Lamont (see also Guggsworth) deal with early instruments 

developed in Germany. (See full citations in the bibliography.) 

' Kellner's article on the much-studied Alexander von Humboldt relates 

specifically to our topic. Geomagnetism was one of the favorite interests of 

the prolific Humboldt, whose own writings can be taken as the starting 

point for the systematic study of geomagnetism. British activity was depicted 

principally in the reports of the BAAS, from Christie, Whewell, and 

especially from Sabine, who succeeded Humboldt as the principle promoter 

of the subject, and in the reports of appropriate committees of the Royal 

Society. It culminated in the Magnetical Instructions of Riddell. John Herschel in turn succeeded Sabine as authority. German work was reported by 

Gauss and Weber, especially in the reports of the "Magnetische Verein." 

(See full citations in the bibliography.) 

•* Fleming has written on early geomagnetic work in the United States. 

Alexander Dallas Bache played a role in the United States similar to that 

of Humboldt and Sabine in Europe, and Locke, Loomis, and Lovering 

periodically reported on observations. Benjamin Silliman, who regularly 

reported on "recent progress," in his American Journal of Science, treated 

geomagnetism in 1846. (Systematic work was done earlier in Canada, thanks 

to the British program for "colonial observatories," associated particularly 

with Lefroy.) Sabine reported in 1846 on the progress of a geomagnetic 

surve)- of North America. Ennis has described the magnetic work of the 

Wilkes Expedition of 1838-1842, and Gillis has written on the work of the 

Naval Astronomical Expedition of 1849-1852, which he headed. Geomagnetic work in North America is frequently touched on in the Papers of 

Joseph Henry, and in the .Annual Reports of the Smithsonian Institution, 

which he headed. Th e Smithsonian's short-lived geomagnetic observatory 

was described by Hiigard. (See full citations in the bibliography.) 

^ L.A. Bauer and CA . Schott were the chief reporters on, as well as the 

chief scientists in, geomagnetic work at the U.S. Coast and Geodetic Survey 

in the later 19ih century. Th e history of the "International Polar Year" 

(1881-1882) was related in the Annals (1959) of the International Geophysical Year. (See full citations in the bibliography.) 

'' Th e epochal work of the Carnegie Institution during the early years of 

the century was reported in its Researches, published during the years 1912-

1917. See also Hazard's report of 1925 and McComb's of 1941. (See full 

citations in the bibliography.) 

43 
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Society of Edinburgh, 14 (1836-1840), pages 1-29. 

Gau.ss. CF . "Observations of the Magnetic Inclination at Gottingen, 

(1841)." In Taylor's Scientific Memoirs, volume 3 (1843), pages 623-665 . 

London. 

(iauss, CF. , and Wilhelm Weber. "Remarks on the Construction of Magnetic Observatories and the Instruments Which They Should Contain." 

44 
NUMBER 48 45 

Annals of Electricity, 3 (1839), pages 92-108 . [Translated from the 

German edition of 1833. Illustrated.] 

. [Five reports on their work at the Gottingen magnetic observatory are printed, in English translation.] In Taylor's Scientific Memoirs, volume 2 (1841). London. [See also Guggsworth, below.] 

. "A General Outline of the Various Theories Which Have 

Been Advanced for the Explantation of Terrestrial Magnetism." Annals 

of Electricity, 1 (1837), pages 117-123 . 

Gilliss, J.M. A Report of the Plan and Construction of the Depot of Charts and 

Instruments . . . Washington, 1845 [Report of the Secretary of the Navy. 

Senate, 28th Congress, 2nd Session.] 

. United States Naval Astronomical Expedition to the Southern 

Hemisphere during the Years 1849-52. In Magnetic and Meteorological 

Observations, volume 6. Washington, 1856. 

Gilpin, George. "Observations on the Variation and Dip of the Magnetic 

Needle, 1786-1805" [at the Royal Society]. PT, 96 (1806), pages 385 -

419. 

Graham, George. "An Account of Observations Made of the Variation of 

the Horizontal Needle at London ... . 1722-23. " PT, 33 (1724), pages 

96-107. 

Graham, J.D. "Observations of the Magnetic Dip Made at Several Positions . . . and of the Magnetic Declination in the United States" (1840). 

Transaction, APS, new series, 9 (1846), pages 329-380. 

Guggsworth, Julian. "Remarks on the Construction of Magnetic Observatories and the Instruments Which They Should Contain. From the 

German of Professors Gauss and Weber." Annals of Electricity, 3 (1839) 

pages 92-109 . 

Halley, Edmund. "A Theory of the Variation of the Magnetical Compass,' 

and "An Account of the Cause of the Changes of the Variation of the 

Magnetical Needle." In Miscellanea Curiosa, volume 2 (1723-1727), 

pages 27-4 2 and 43-60 . London. 

Hansteen, Christian. Untersuchungen von den Magnetismus der Erde. Christiana [Oslo], 1819. 

. "Beobachtungen iiber die Intensitat des Magnetismus im 

nordlichen Europa." Annalen der Physik, 3 (1825), pages 225-234. 

Harvard University, Fogg Art Museum. Early Science at Harvard. Cambridge, Mass., 1969. [An exhibibion catalog.] 

Ha7.ard, D.J. "Terrestrial Magnetism in the Twentieth Century."yowrna/ 

of the Washington Academy of Sciences, 15 (1925), pages 111-125. 

Heathcote, N.H. deV^, and A. Armitage. Annals of the International Geophysical Year, 1: The Histories of the International Polar Years and the 

Inception and Development of the International Geophysical Year. Washington, 1959. 

Heck, N.H. "The Magnetic Survey of the United States." Proceedings, 

APS, 84 (1941), pages 205-224 . 

Herschel, John. "Terrestrial Magnetism.' In Herschel, Essays from the 

Edinburgh and Quarterly Review, 1857, pages 63-141 . London. 

Herschel, John, editor. Admiralty Manual of Scientific Inquiry. London, ca. 

1840. [Sabine discusses geomagnetism in section 2.] 

Hiigard, J.E. "Description of the Magnetic Observatory at the Smithsonian 

Institution." Smithsonian Institution Annual Report for 1859, pages 385 -

395. 

Hoogewerff, J.A. "Magnetic Observation at the United States Naval Observatory, 1888 and 1889." In Washington Observations, Appendix 1. 

Washington, 1890. 

Humboldt, Alexander von. "Ueber die Mittel, die Ergriindung einiger 

Phanomene des tellurischen Magnetismus zu erleichtern." Annalen der 

Physik und Chemie, 15 (1829), pages 319-336. 

. "Beobachtungen der Intensitat magnetischer Krafte und der 

magnetischen Neigung, angestellt in denjahre n 1798 bis 1803, von 

48''50 ' NB bis 12° SB und 3''2' OL bis I06°22 ' WL, in Frankreich, 

Spanien, den canarischen Inseln, dem Atlantischen Ozean, America und 

der Sudsee." Annalen der Physik und Chemie, 15 (1829), pages 336-362. 

Kellner, L. "Alexander von Humboldt and the Organization of International Collaboration in Geophysical Research.' Contemporary Physics, 2 

(1959), pages 35-48 . 

Kreil, Karl. [Letter to A. T. Kupffer.] Philosophical Magazine, series 3, 14 

(1840), pages 241-250. [On instruments and observations at Milan (Kreil) 

and St. Petersburg (Kupffer).] 

Lamont, Johann von. "An Account of the Magnetic Observatory and 

Instruments at Munich." In Taylor's Scientific Memoirs, volume 3 (1843), 

pages 499-526. London. 

. Handbuch der Erdmagnetismus. Berlin, 1849. 

Lefroy, J.H. Diary of a Magnetic Survey of a Portion of the Dominion of 

Canada (1842-44). London, 1883. 

. "On the Application of Photography to the Self-registration 

of Magnetic and Meteorological Instruments." AJS, series 2, 9 (1850), 

pages 319-324. 

Lefroy, Lady, editor. Autobiography of General Sir John Henry Lefroy. 

London, n.d. [1895]. [For private circulation. Ther e is a copy in the 

library of the Universitv of Toronto.] 

Lloyd, Humphrey. "Further Development of a Method of Observing the 

Dip and the Magnetic Intensity at the Same Time with the Same Instrument." Transactions of the Royal Irish Academy, 17 (1837), pages 449-460 . 

. "An Attempt to Facilitate Measurement of Terrestrial Magnetism." Transactions of the Royal Irish Academy, 17 (2) (1837), page 159. 

. "On a Declination Instrument, Made for the Magnetical 

Observatory of Dublin." Annals of Electricity, 3 (1839), pages Ib-ll. 

"On a New Magnetical Instrument for the Measurement of 

the Inclination and Its Changes.' Proceedings of the Royal Irish Academy, 

2(1840-1844), pages 115-117. 

"On the Determination of the Intensity of the Earth's Magnetic Force in Absolute Measure." Transactions of the Royal Irish Academy, 

21 (1846), pages 3-11 . 

Lloyd, Humphrey, Edward Sabine, and J.C. Ross. "Observations on the 

Direction and Intensity of the Terrestrial Magnetic Force in Ireland." 

BAAS, Report for 1835. 

Locke, John. "On the Magnetic Dip . . . Ohio (1837-38)." Transactions, 

APS, new series, 6 (1839). page 267-273 . 

. "On Terrestrial Magnetism." >4yS, 40 (1841), pages 149-156. 

[Concerns his work in the Ohio Valley.] 

. "Observations to Determine the Horizontal Magnetic Intensity and Dip at Lexington, Ky. and Cincinnati," Transactions, APS, new 

series, 7 (1841), pages 261-264. 

. "Observations Made in the Years 1838, '40, '41 , '42, and '43 

to Determine the Magnetical Dip and the Intensity of Magnetical Force, 

in Several parts of the United States." Transactions, APS, new series, 9 

(1846), pages 283-328. 

Loomis, Elias. "Observations on the Variation of the Magnetic Needle, 

Made at Yale College in 1834 and 1835." AJS, 30 (1836), pages 221 -

233. 

. "On the Variation and Dip of the Magnetic Needle in different Parts of the United States." AJS, 34 (1838), pages 290-307. 

. "On the Magnetic Dip in the United States." AJS, 40 (1841), 

pages 85-92. 

. "Observations to Determine the Magnetic Dip . . . Ohio and 

Michigan." Transactions, APS, new series, 7 (1841), pages 1-6. 

"Observations to Determine the magnetic Intensity 

Transactions, APS, new series, 8 (1843), pages 61-72 . 

. "Notice of Some Recent Additions to Our Knowledge of the 

Magnetism of the United States and Its Vicinity.' AJS, 2nd series, 4 

(1847), pages 192-198. 

Lovering, Joseph. "An Account of the Magnetic Observations Made at 

the Observatory of Harvard University, Cambridge." Memoir of the American Academy of .Arts and Sciences, new series, 2 (1846), pages 85-160. 

Lovering, Joseph, and W.C. Bond. "An Account of the Magnetic Observations Made at the Observatory of Harvard University." Memoirs of the 

American .Academy of .Arts and Sciences, new series, 2 (1846), pages 1-84. 

McConib, H. E. "Geomagnetic Observatories and Instruments." Proceedings, APS. 84 (1941), pages 239-255 . 

. Magnetic Observatory Manual. Washington, 1952 (USC&GS 

Special Publication 283). 
46 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

McConnell, Anita. Geomagnetic Instruments before 1900. London: Harriet 

Wynter, 1980. 

Mitchell, A. C "Chapters in the Hi.story of Terrestrial Magnetism." TM, 

37 (1932), pages 105-146, 42 (1937), pages 241-280, 44 (1939), pages 

77-80 . [A meticulous history up to about 1500.] 

Mottelay, A.C. Bibliographical History of Electricity and Magnetism. London, 

1922. 

Quetelet, L.A.J. Sur I'etat du magnetisme terrestre a Bruxelles ... . Brussels, 

1839. 

[Quetelet, L.A J.] "Sur le magnetisme terrestre en Italic" [1841]. In A.D. 

Bache, Miscellaneous Papers and Manuscripts, volume 6 [in Smithsonian 

Institution Library, reprint from the Memoirs of the Academy of Sciences, 

Brussels]. 

Reichelderfer, F. W. "The Contributions of [Charles] Wilkes to Terrestrial 

Magnetism, Gravity and Meteorology." Proceedings, APS, 82 (1940), 

pages 583-600. 

Reingold, Nathan, edxior. Joseph Henry Papers. Volume 1 (1797-1832), 

Wa.shington, 1972; volume 2 (1832-1835), Washington, 1975. [Contain 

numerous references to geomagnetism.] 

Riddell, C.J.B. Magnetical Instructions. London, 1844. 

Ronalds, Francis. "On Photographic Self-registering Meteorological and 

Magnetical Instruments." fT, 137 (1847), pages 111-117. 

Ross, J.C. "On the Position of the North Magnetic Pole" (1833). In A. D. 

Bache, Miscellaneous Papers and Manuscripts, volume 6 [in the Smithsonian Institution Library]. 

Royal Society of London. Report of the Committee of Physics, including 

Meteorology, on the Objects of Scientific Inquiry in These Subjects. London, 

1840. [Begins (pp. 1-37) with the Society's formal discussion of the 

methods and instruments to be used at the Colonial Observatories.] 

Royal Society of London, Committee of Physics and Meteorology. Revised 

Instructions for the Use of the Magnetic and Meteorological Observatories and 

for the Magnetic Surveys. London, 1842. 

Rumbaugh, L. H., and L. R. Alldredge. "Airborne Equipment for Geomagnetic Measurements." Transactions of the American Geophysical Union, 

20(1949), pages 836-848 . 

Sabine, Edward. "Observations on the Direction and Intensity of the 

Terrestrial Magnetic Force in Scotland" (1836). In A.D. Bache, Miscellaneous Papers and Manuscripts, volume 18 [in the Smithsonian Institution 

Library]. 

. " Report on the Variations of the Magnetic I ntensity Observed 

at Different Points of the Earth's Surface." Report, BAAS, 7 (1838), pages 

1-42. 

. "A Memoir on the Magnetic Isoclinal and Isodynamic Lines 

in the British Islands," Report, BAAS, 7 (1838), pages 49-195 . 

[Letter to John Herschel.] In A.D. Bache, Miscellaneous Papers and Manuscripts, volume 18 [in the Smithsonian Institution Library]. [Recommendations concerning the observatory to be established 

at Toronto.] 

"Magnetic Observations" (n.d., ca. 1840). In A.D Bache, 

Miscelaneous Papers and Manuscripts, volume 18 [in the Smithsonian 

Institution Library]. [On instruments used by Captain Fitzroy (of the 

Beagle) and others.] 

"A Magnetic Survey of a Considerable Portion of the North 

American Continent," PT, 136 (1846), pages 237-336 . 

'On the Means Adopted in the British Colonial Magnetic 

Observatories for Determining the Absolute Values, Secular Change, 

and Annual Variation of the Magnetic Force," PT, 140 (1850), pages 

201-219 . 

. Manual of Terrestrial Magnetism. London, 1859. 

Contributions to Terrestrial Magnetism, 1840-78 . n.p., n.d. 

[Articles published in PT between these dates are here collected in two 

volumes (Library of Congress).] 

Saussure, Benidict de. Voyage dans les Alps. 4 volumes. Neuchatel, 1779-

1796. [Describes his "pendulum" magnetometer (volume 1, pages 375 -

381).] 

Schott, CA . "Instructions for Magnetical Observations." USC&:GS Report 

for 1872, Appendix 16. 

. "Directions for Magnetic Observations with Portable Instruments." USC&GS Report for 1881, Appendix 8. 

. "Magnetic Survey of North America," United States Weather 

Bureau, Bulletin, II, 1893, pages 460-468 . 

[Silliman. Benjamin]. "Recent Progress of Magnetical and Meteorological 

Science." AJS, series 2, 1 (1846), pages 137-145 . 

Smithsonian Institution. Annual Report, for the years 1850-1865 . [Smithsonian geomagnetic activities are described in the narrative portion of 

nearly every volume during these years.] 

United Slates Coast and Geodetic Survey. Magnetic Observatory Results. 

[Volumes in this series were produced periodically for each observatory 

(Cheltenham, Tucson, Baldwin (Kansas), Honolulu, etc.)] 

Whewell, William. "Report on the Recent Progress and Present Condition 

of the Mathematical Theories of Electricity, Magnetism, and Heat." 

BAAS, Report for 1835, 1-34. 

Wilkes, Charles. "Hydrography." In Report of the United States Exploring 

Expedition during the Years 1838-42, volume 23. Philadelphia, 1861. 
NUMBER 48 47 

FIGURE 31.—No. 1, Declinometer, Gambey Type, ca. 1830. 

Henri-Prudence Gambey (1787-1847), reputedly the favorite instrument-maker of Arago and Humboldt, came into prominence in 1819. 

During the next few years he made a number of intricate instruments, 

including an improved geomagnetic compass for Coulomb. Th e instrument 

shown exemplifies this fundamental Gambey instrument, as it was illustrated 

in textbooks for a half century. It is unmarked, and may have been made 

by another maker. 

Construction is of marble, brass, and ivory, the 11 '/2-in/49-cm bar 

magnet being supported by a thread, and its position being read by small 

microscopes on each end. 

FIGURE 32.—No. 2, \'ariation Transit, Gambey. 

This instrument was acquired by Alexander Dallas Bache during his 

European tour of 1836-1838, and was used to determine declination in 

Bache's magnetic survey of Pennsylvania, 1840-1843. It is a portable 

version of No. 1, Figure 31 in the present collection, and is smaller and 

lighter. It also includes a transit telescope for the determination of geographic north; thus its name, "variation transit." 

T h e instrument was sold to the Cincinatti Observatory in 1869, given 

by them to the Carnegie Institution in 1915, and in 1959 to the historical 

collections of the Smithsonian. 

[Reference: A.D. Bache, in Smithsonian Contributions to Knowledge, volume 

13, 1863, Art. VIII.] 
48 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 33.-No. 3, Magnetometer, mid-19th century. 

This unmarked instrument shows the essential features of the simple 

Lamont magnetometer, with a short bar-magnet and horizontal supports 

for defiection bars (which are missing). 

if 

FIGURE 34.—No. 4, Magnetometer for School Demonstration, 1962. 

This miniature instrument (the bar magnet is 4 in/9.2 cm long) was 

made by Griffin &: George, Ltd., London. A virtually identical instrument 

is shown in J.B. Biot, Precis elementaire de physique experimentale (Paris, 

1817), although subsequent texts describe it as "Weber's apparatus for 

observing oscillation." 
NUMBER 48 49 

F 1 

FIGURE 35.—No. 6, Magnetometer, Grunow, ca. 1870. 

As shown at the left the instrument is set up for measuring declination; 

at the right, for intensity, by Gauss's method. Th e suspension tube is 39 

in/99 cm long, the declination magnet is a one-in/2.5-cm bar. 

William Grunow (1830-after 1900), a native of Berlin, came to the 

United States (New Haven, Conn.) in 1850, moved to New York City in 

1861, and by 1873 was "established" at Columbia College (later University). 
50 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 36.—No. 8, Magnetograph, Adie, ca. 1880. 

For a general description of the Adie magnetograph see Figure 23. 

Shown here is the Coast Survey instrument, probably at its initial location, 

the Los Angeles observatory. In 1890 the instrument was moved to San 

Antonio, Texas, being transferred soon thereafter to the outskirts of the 

city to avoid electrical disturbances resulting from the introduction of the 

street railway. Th e San Antonio station was abandoned in 1895, but the 

Adie magnetrograph was reinstalled at Cheltenham, Md., in 1902, as a 

back-up for the newer Eschenhagen-Topfer variometers (No. 24, Figure 

53) at the Survey's primary observatory. It was used for direct visual 

reading, and was still in use in 1942. 

[References: BAAS Report for 1859. L.A. Bauer, in TM, 4 (1899), and in 

CS Annual Report, 1902.] 

FIGURE 37 (facing page).—No. 9, Magnetometer, Kew Type . 

A portable compound instrument, incorporating a theodolite, declinometer, and magnetometer, for measuring declination and intensity, 

designed at Kew Observatory and made by Joh n Dover (1824-1881), or, 

more probably, his son. 

On the use of the instrument see Figure 29. Kew instruments identical 

to this were illustrated as early as 1880, but this instrument may have been 

made later—or it was long in use. It was the property of the U.S. Navy 

Hydrographic Office, for which it was calibrated at the Coast Survey's 

Cheltenham, Md., observatory in 1945 and 1950. Th e same type was used 

by the Carnegie Institution in China and Africa in the early 20th century. 

[Reference: CIW, Land Magnetic Observations, 1905-10 (Washington, 

1912).] 
NUMBER 48 51 

«t>* / / / 
52 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
NUMBER 48 53 

h 

FIGURE 38 (facing page).—No. 10, Magnetometer, Brunner-Chasselon, ca. 

1884. 

Designed by Brunner and constructed by Chasselon, of Paris, this was 

the standard instrument of the French Magnetic Survey towards the end 

of the 19th century. Its principal feature was its diminutive size and 

portability. Th e magnet is a 2'/2-in/6.4-cm cylindrical steel bar, suspended 

by a silk fiber and carrying concave mirrors, by which the user reads the 

direction through a microscope. Ther e is also an integral theodolite. 

The Coast Survey used this instrument for about a decade, it being a 

favorite of L.A. Bauer, for measurement of declination and horizontal 

intensity on his tours of inspection of observatories. Although defects were 

found, resulting in systematically low values (attributed to impurities in the 

brass housing) and in variations of torsion due to the light weight of the 

magnet, its readings were found to be consistent, and hence susceptible to 

compensation. Some use was also made of it in the early work of the 

Carnegie Institution. 

The instrument was used in conjunction with the Chasselon dip circle 

(No. 35, Figures 61 , 64). 

[Reference: Annates de Bureau Centrale Meteorologique de France, 1884.] 

FIGURE 39.—No. 11. Field Magnetometer, Coast Survey, 1892-1893. 

In 1890 a board was appointed by the Superintendent of the Coast 

Survey to consider the improvement of magnetometers, with which it now 

had fifty years of experience. Th e Survey's instrument shop cooperated in 

the design of this instrument, one of four constructed at this time. 

Both the experimental and conservative sides of the agency are seen in 

this instrument. Its general form is that of the "theodolite-magnetometer" 

long in use; that is, a magnetometer and reading telescope are mounted on 

a single axis, with a separate theodolite for astronomical alignment. Changes 

were cautiously made: a slight increase in size, the use of octagonal magnets 

(2^16 in/6.5 cm long) in place of cylindrical ones, and the introduction of a 

black velvet tube between the telescope and the magnet housing, to block 

out air currents and external light. Th e octagonal magnets were designed 

to facilitate inversion and balance, but were found to be magnetically 

irregular and were abandoned. Th e design was on the whole successful, 

and these magnetometers were used in the comprehensive magnetic survey 

of the United States that began in 1899. 

[Reference: Coast Survey Annual Report for 1894, pages 265-275.] 
54 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 40.—Because geomagnetic instruments had to be transported, 

often manually, in rough terrain, the design of boxes for them was almost 

as complex a task as the design of the instruments themselves. Shown here 

is our magnetometer No. 15, Figure 44 (CIW 4) in its box. 
NUMBER 48 55 

FIGURE 41.—No. 12, "Magnettheodolit," Eschenhagen-Tesdorpf, ca. 1900. 

Described by the Coast Survey as "the Prussian field magnetometer," 

this instrument was designed by J.F.A.M. Eschenhagen (1858-1901), Director of the Prussian Magnetic Observatory at Potsdam, and built by the 

firm of L. Tesdorpf, of Stuttgart. It combines a theodolite, magnetometer 

(3.5-cm/iy8-in magnet), declinometer and dip circle, on the same base. Th e 

arrangement for deflection is shown on the right, where the telescope 

is mounted on the same base as the suspension of the 2.9-cm/l '/s-in magnet, 

and moves around a vertical axis with the deflected image. Th e arrangement for declination, adjacent to the left, is also mounted on the same base. 

T h e theodolite is shown at the far left. 

Although it was advertised as portable, the Coast Survey acquired this 

instrument, about 1900, as an observatory instrument for its station at 

Sitka, Alaska, where it was used to calibrate field instruments used in the 

northwest part of the country. Its partial reassembly was required to switch 

from one measurement to another, and it appears to have been judged too 

complicated. It was retired about 1904, although subsequently used by the 

Carnegie Institution at Samoa and other Pacific Islands. 

[Reference: K. Haussmann, "Der Magnettheodolit von Eschenhagen-Tesdorpf," Zeitschrift fuer Instrumentenkunde, 1906, 26, pages 2-15.) 
56 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
NUMBER 48 57 

FIGURE 42 (facing page).—No. 13, Magnetometer, Wild-Edelmann, 1902. 

This instrument derived from an 1893 design by Heinrich Wild (d. 

1902), a Swiss who directed the Russian meteorological service from 1865 

to 1895, and was built by M.T. Edelmann (1845-1913) in Munich. A 

"theodolite-magnetometer," it represents a stage in a sequence of instruments descending from Gauss, through Lamont and Weber. 

Although it was intended as a field instrument, its bulk and complexity 

were found too great for American use and the Coast Survey installed this 

example in the permanent observatory in Honolulu. It was used there until 

1927, when it was replaced by a magnetometer of the India Survey pattern. 

[Reference: M.T. Edelmann, Untersuchung iiber die Bestimmung der erdmagnelische Inclination, 1881.] 

FIGURE 43.—No. 14, Magnetometer, CIW 1, ca. 1902. 

T h e early dependence of the Carnegie Institution's Department of 

Terrestrial Magnetism on the Coast Survey is easily seen in its first instrument, which differs from the contemporary Survey instrument (see No. 11, 

Figure 39) only in minor details. Th e magnets have the same octagonal 

shape, it uses the same peculiar deflection bars, and the optical system is 

essentially the same. The instrument was constructed by the firm of Bausch, 

Lomb, and SaegmuUer, of Washington and Rochester, N.Y. 
58 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 44.—No. 15, Magnetometer, CIW 4, ca. 1905. 

After using borrowed instruments for a few years, improved instruments 

were designed at the Carnegie Institution, whose Department of Terrestrial 

Magnetism was headed by L.A. Bauer, previously head of magnetic work 

at the Coast Survey. This is no. 4 of type 1, and was modeled after the 

corresponding Coast Survey instrument and that of the British India Survey. 

It was made by Bausch, Lomb, and SaegmuUer. Modifications included the 

replacement of hollow octagonal magnets with perfectly cylindrical ones 

"to eliminate questions .. . of irregularities." Magnets 1.4 and 3.0 in/3.5 

and 7.5 cm, of equal weight, were enclosed in aluminum or gold-plated 

brass. Th e silk suspension was replaced with one of phosphor-bronze. A 

damping bar was adopted from the magnetometer of the India Survey (see 

No. 21 , Figure 50). Th e principle defect of this instrument was its weight, 

65 lb/29.5 kg. 

T h e instrument was used on the CIW ships Galilee and Carnegie. 

[Reference: CIW, Land Magnetic Observations, 1905-10 (Washington, 

1912).] 
NUMBER 48 59 

FIGURE 45.—NO . 16, Magnetometer, CIW 8, 1906. 

This is one of nine instruments made not long after 1905, constituting 

a "second generation" of Carnegie instruments, differing mainly in being 

lighter than the first. Th e cylindrical magnets are the same size as those in 

CIW 4 (No. 15, Figure 44). 

This particular instrument was modified for use by Roald Amundsen 

(1872-1928) on his North Polar expedition, I9I8-1920 , the modifications 

involving sealing to avoid condensation and modification of the controls to 

facilitate use of the instrument while wearing heavy mittens. In addition. 

all metal clamps and other parts frequently touched were covered with 

ivory-like celluloid. 

T h e instrument accompanied Amundsen on the first voyage of the 

Maud, 1918-1920, as he drifted eastward from Norway to the Bering 

Straits, over the roof of Asia. Th e Carnegie Institution subsequently published the results. 

[Reference: CIW, Land Magnetic Observations, /PZ-Z-yP (Washington, 1921) 

pages 8ff.] 
60 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Hi 
NUMBER 48 61 

FIGURE 46 (facing page).—No. 17, Universal Magnetometer, CIW 19, 

1911. 

This instrument, one of five designed and built at the DTM, was more 

truly "universal" than earlier instruments so designated, since it incorporated a declinometer-magnetometer with a theodolite and a dip circle in a 

single unit and required little manipulation to switch functions. Its weight, 

37.5 lb/17 kg, was only Vs that of the first generation of magnetometers 

designed by the Carnegie's DTM. 

The instrument combines a magnetometer (with magnets I and 2.2 in/ 

2.6 and 5.6 cm in length) and a dip circle, both located within a single box, 

the mounting of the magnetometer needle being moved aside for measurement of inclination. 

[Reference: CIW, Land Magnetic Observations, 1911-13 Washington, 

1915).] 

FIGURE 47.—No. 18, Universal Magnetometer, CIW 21 , 1911. 

Few instruments have traveled so much as this one. During 1911-1914 

it was used in nearly every country of Central and South America, notwithstanding political turmoil (in Brazil it was escorted by a "Colonel-in-command of the revolutionary forces"). In 538 days in the field with a Mr. 

Powers it traveled 430 miles by sailboat, 705 miles by railway, 65 miles by 

handcar, 700 miles by canoe, 40 miles by coach, 110 miles by muleback, 

and 90 miles on foot with oxcart. In 1915-1916 it was used on the fourth 

cruise of the ship Carnegie, a circumnavigation, and it somehow survived 

the accidental burning of the Carnegie on its seventh and final voyage in 

1929. Admiral Richard Byrd took it in 1934-1935 to his Antarctic base. 

Little America, whence it was carried by a research party to an interior 

plateau. Its service ended in 1937 on loan to Gulf Research and Development Company for exploratory surveying in Kuwait and Iraq. 

Technically the instrument is nearly identical to CIW 19 (No. 17, Figure 

46). 
62 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 48.—No. 19, Magnetometer and Earth Inductor, CIW 26, ca. 

1913. 

T h e magnetometer (left), designed and built at the DTM, was a further 

improvement on CIW 21 (No. 18, Figure 47). Th e cylindrical magnets, 

suspended by phosphor-bronze wire, are identical to those of CIW 19 (No. 

17, Figure 46). 

T h e principal innovation was the replacement of the dip circle with an 

earth inductor (center, with its galvanometer to the right). Th e inductor, 

whose circle has an outer diameter of 2.8 in/71 mm, is the type used on 

land. It indicates the direction of the earth's magnetic field by a "null 

method." Tha t is, when the rotor moves around its axis but is oriented in 

some other direction than the earth's field, a current is indicated in the 

galvanometer. Th e absence of this current indicates that its axis lies in the 

direction of the field. This direction is then read off a vertical scale, using 

two reading microscopes. Another telescope, mounted on the instrument 

and parallel to the axis of rotation, is used for geographic alignment. 

T h e instrument is also notable for its light weight, 15.9 lb/7.2 kg 

(although the tripods and box increase the total to 48.7 lb/22.1 kg) 

CIW 26 is mentioned in the Carnegie Institution report for 1911-1913, 

and was taken to England in 1915 for comparison with standard instruments 

at Kew and Greenwich. Later in that year it was at the Coast Survey 

observatory at Cheltenham, Md. Thereafter it was taken on tours almost 

every year for three decades, being used in the United States, South 

America, Africa, and on the sixth cruise of the ship Carnegie. One of its 

main functions was the redetermination of the magnetic elements at stations 

that had been "occupied" ten or twenty years earlier, providing data on the 

secular variation of the magnetic elements. It was also used to coordinate 

the observations of remote observatories, such as San Juan (Puerto Rico) 

and Huancayo (Peru). 

[References: J.A. Fleming, in TM, 16 (1911), and (with J.A. Widner) 18 

(1913).] 
NUMBER 48 63 

•^^S . 

FIGURE 49.—Observation of horizontal intensity, with a magnetometer that 

is similar to No. 19 (Figure 48), November 1930. R.R. Bodle, standing; 

W.M. Hill, recording. 
64 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 50.—No. 21 (?), Magnetometer, British India Survey Pattern. 

This instrument is used to determine deflection and intensity, the latter 

by vibrations, employing a cylindrical magnet 3.65 in/9.3 cm long, suspended by a thread of phosphor-bronze. Th e magnet is observed through 

the telescope, which contains a scaled optical glass and is illuminated by an 

oil lamp. 

This type of magnetometer apparently dates from 1906, when six 

instruments were supplied to the British India Survey. All were made by 

the firm of Cooke & Sons of London, as were one or more instruments 

later acquired by the Coast Survey. Th e instrument shown here, in use at 

the Sitka, Alaska, observatory, may not be our No. 21 . Ours is, however, 

shown in Figure 74, with the Nelson induction apparatus. 

I Reference: TM, 6 (1901), pages 65ff ] 
NUMBER 48 65 

/ece 

RefUcfftfg 

Mirror 

Objccfive, 

Knife Edge Mirror 

FIGURE 51.—No. 22, Magnetometer, Schmidt. 

Invented by Adolf Schmidt in 1915, this "magnetic vertical balance" 

represents a refinement of Lloyd's vertical force magnetometer (see text 

and Figure 18). Th e instrument, which is essentially a variometer, is 

oriented in the magnetic meridian through the use of a separate compass. 

The deflection of the magnetized balance beam is then measured through 

an optical system visible through the small telescope at the top. 

With this instrument the .scientific and the prospecting magnetometers 

became one. Instruments of this type have been used in mineral prospectin<^ 

in the United States since the 1920s. Our example was made by Gulf 

Research and Development Corp. of Pittsburgh. 

Shown here is a cross-sectional drawing of the instrument. 

[ References: Berichte uber der Taetigkeit der preussische meteorologische Institut 

(Berlin), 1915-1916. TM, 21 (1916), pages 32, 33. Th e drawing is taken 

from J.A. Fleming, Terrestrial Magnetism and Electricity, New York: McGraw-Hill. 1938. page 120.] 
66 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

•^3F 4 

M 

FIGURE 52.—No. 23, Variometers, Edelmann, ca. 1890. 

Thoma s Edelmann, of Munich, was one of the most prolific designers of 

magnetic apparatus in the late 19th century. He was famous both for the 

complexity and the massiveness of his designs. Coast Survey magnetometer 

22 (No. 13, Figure 42) clearly exhibits the first quality, and these two 

variometers display the other. Marble is used extensively in these instruments, and especially in the 48-in/122-cm high declination variometer 

(right, the needle, about 5 in/13 cm long, is missing). They were used with 

light sources and photographic recording apparatus similar to that shown 

in Figure 30. 

[Reference: M.T. Edelmann, "On the Construction of Earth-Magnetic 

Instruments," United States Weather Bureau, Bulletin 11, 1894.] 
NUMBER 48 67 

FIGURE 53.—No. 24, Variometers, Eschenhagen-Toepfer, ca. 1900. 

These instruments measure variations in declination (left, 20V8 in/53 

cm high) and horizontal intensity (right). Th e magnet housings are 1 '/a-in/ 

3.8-cm square bronze boxes. A third instrument, not in the collection, 

measured vertical intensity. They were used at Cheltenham, Md., Honolulu, 

and at Baldwin, Kansas. These (or similar instruments) are shown in Figure 

54 being tested at the Carnegie Institution. 

\'ariometers require frequent callibration against "absolute" instruments, such as Coast Survey magnetometer 18, (No. 11, Figure 39). 
68 

SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 54.—Eschenhagen-Toepfer variometers mounted for tests at the 

DTM, May, 1916. Th e two tall instruments are similar, if not identical, to 

those in the present collection (No. 24, Figure 53). 
NUMBER 48 69 

FIGURE 55 (upper).—No. 25, Variometers, Ruska, 1950s. 

The effort to incorporate electrical methods into the measurement of 

the earth's magnetic elements was one of the most important instrumental 

developments of the first half of the 20th century. It was made possible by 

the development of apparatus capable of maintaining a constant magnetic 

field. In these instruments, made by the Ruska Instrument Co. of Houston, 

Texas, the field is supplied by 12-in/30.5-cm Helmholtz coils that surround 

the magnet housings. 

T h e instruments are for determining changes in vertical force (left, 0.4-

in/l-cm needle) and both declination and horizontal force (right, 3.1-in/8-

cm needle). 

FIGURE 56 (lowei).—Ruska variometers at Cheltenham, Md., observatory, 

about 1960. Th e instruments are for measuring vertical intensity (right), 

declination (center), and horizontal intensity (left). Th e box on the far left 

contains the photo recorder. 
70 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 57.—No. 26, Magnetometer, Airborne, Gulf, ca. 1940. 

Developed in 1940 at the Gulf Research and Development Company, 

for the primary purpose of mineral exploration, this instrument generates 

a steady magnetic force, induced by an electrical system within the instrument. This magnetic force varies in response to changes in the ambient 

field, that is, the earth's magnetism in the vicinity. 

T h e instrument is designed to avoid the effects of shock by eliminating 

mechanical parts, measuring instead the saturation effects of the magnetic 

environment on high-permeability magnetic material such as permalloy (a 

magnetic alloy of nickle). Nevertheless, because of the vibration and instability of the aircraft, the instrument was towed behind the plane in a 

torpedo-like housing, called the "bird." 

Only the "bird," 55% in/142 cm long (sectioned to show the interior), is 

shown in this illustration. 

[Reference: Gary Muffley, "The Airborne Magnetometer," Geophysics, 11 

(1946).] 
NUMBER 48 71 

FIGURE 58.—No. 27, Magnetometer, Airborne, U.S. Naval. Hydrographic 

Office, VAM-2B3, 1953. 

Experiments made in the early 1940s on the possibility of submarine 

detection with the airborne magnetometer used the recently introduced 

Gulf instrument (No. 26, Figure 57). They were sufficiently promising to 

justify a "crash program" for the improvement of the instrument which, as 

was typical of wartime research, involved many institutions, including 

Columbia University, the General Electric Company, the Sperry Gyroscope 

Company, the Naval Ordnance Laboratory, and the Bell Telephone Laboratories. Th e result was MAD (Magnetic Airborne Detector), a complex 

system in which the sensing element was located within the aircraft. 

T h e sensing unit (35.54 in/90 cm high) is in the center of this photograph, which shows all components. It continuously records the total 

intensity of the field and the magnitudes of directional angles. This is the 

second version (Type 2A) of the instrument. 

[Reference: E.O. Schonstedt and H.R. Irons, Trans., .American Geophysical 

Union, 36 (1955), pages 25-41.] 
72 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

4 ll il l il fl Ik h 

tJhiversiiy o l Vermont 

HE DIP NEEDLE 

S the inclination of the earth's magM relative to the earth's surface. 

FIGURE 59.—No. 28, Dip Circle, for classroom demonstration, early 19th 

century. 

This instrument, used at the University of Vermont, has the ornate 

construction typical of apparatus used for demonstrating science at that 

time. It was easily oriented, using the circular scale at the top. Th e 6-in/ 

15.2-cm needle, jewel mounted, is hidden in the photograph by the vertical 

mounting bracket. 
NUMBER 48 73 

FIGURE 60.—No. 30, Dip Circle, Barrow, ca. 1860. 

Henry Barrow (1790-1870), successor to the celebrated English instrument-maker, T.C. Robinson (d. 1841), supplied magnetic instruments to 

the U.S. Naval Observatory in the early 1840s, and subsequently to the 

Coast Survey, which reported Barrow circles to be the standard instrument 

as late as 1877. 

This instrument, CS 9, is presumably earlier than CS 10 (No. 31 , Figure 

61), which was in use in 1863. Details of its employment are unknown. Th e 

position of the 9'/2-in/24-cm needle is read by two magnifying lenses 180 

degrees apart. 

[Reference: Coast Survey, .Annual Report, 1872.] 
74 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 61.—Nos. 31, 35, 38, Inclinometers (Dip Circles), ca. 1860-1900. 

T h e instrument at the right (No. 31) was made about 1863 by William 

Wurdemann (1811-1900), a native of Bremen. Wurdemann was brought 

to the United States by the first Director of the Coast Survey, F.R. Hassler, 

in 1834. He resided in Washington until his death, working intermittently 

for the Survey (1834-1836, 1848, 1870-1874) and as an independent 

in.strument maker. He made some of the early instruments of the survey, 

including this one, apparently made while he was in private business. Th e 

needle (missing) was about 9 in/23 cm long. Th e instrument was used in 

Washington in 1863 and subsequently at many other locations, including 

points on the west coast from Sitka to San Diego in 1881. 

Shown in the center is the Bruner-Chasselon dip circle (No. 35) whose 

2.75-in/7-cm needle is located within a 3V8-in/9.9-cm circle. This instrument is also illustrated in Figure 64. 

At the left is a Lloyd-Creak dip circle (No. 38) which is nearly identical 

to No. 37, Figure 65. 
NUMBER 48 75 

FIGURE 62.—No. 34, Dip Circle, Dover 85, ca. 1880. 

This type of circle became the most common in the United States in the 

late 19th century, and was commonly known as the Kew dip circle regardless 

of the maker. Th e housing for the 3-in/7.6-cm needle (which is missing) is 

a rectangular wooden box with a glass front and back, and the scale and 

reading mechanisms are mounted in front of the box. A special mounting 

for a defiection magnet was usually installed on the reading mechanism, to 

allow the total intensity to be determined by Lloyd's method, in which the 

position of the needle with and without an adjacent defiecting bar are 

compared. 
76 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 63.—Nos. 33, 36, 40, Dip Circles, Dover. 

These three dip circles are similar to Dover 85 (Figure 62). Th e instrument at the left is our No. 33. Tha t in the center. No. 36, was used during 

the International Polar Year, 1932-1933. Th e instrument at the right is 

our No. 40. 

John Dover (1824-1881), of London, was an apprentice of T.C. Robinson, and although Henry Barrow became Robinson's successor, Dover went 

into the business independently. He exhibited a balance at the Great 

Exhibition of London, 1851. By 1869 he had moved to (New) Charlton, 

Kent, not far from the Royal Observatory at Greenwich. In 1880 the 

observatory records mention that Dover had "nearly completed" a "dip 

instrument," and, as no. 187, the instrument was soon in use at Greenwich 

and was in use (elsewhere) as late as 1914. It is assumed that Dover had 

made such instruments earlier, although surely not 186 of them! The 

numbers were probably coded. It has been reported that Dover's son, A. 

W. Dover, customarily added his initials to instruments of his own manufacture, although this has not been found on any of the instruments in the 

present collection. This type of circle became the most common in the 

United States in the late 19th century. 
NUMBER 48 77 

FIGURE 64.—Nos. 10 and 35, Magnetometer (left) and Dip Circle (right), the later 19th century, acquired by the Coast Survey about 1900, are also 

Brunner-Chasselon, ca. 1884. shown in Figures 38 and 61 , where they are described. 

These examples of instruments used in the French Magnetic Survey in 
78 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

omg^' 

FIGURE 65.—NO . 37, Dip Circle, Lloyd-Creak, Dover 168, ca. 1900. 

T h e Fox dip circle (see text) had been modified for observation at sea 

in 1839. Captain Ettrick Creak, long Superintendent of the Compass 

Dejaartment of the British Admiralty, undertook the improvement of the 

instrument, after an Arctic voyage of 1875-1876, the result being this 

instrument. Th e circle is 5V8 in/15 cm in diameter. 

This example was made by Dover, and was referred to by an American 

source as "new" in 1901. It embodies Lloyd's total intensity method (see 

Figure 62), and was further modified by E.G. Fischer at the Coast Survey, 

to improve its performance near the magnetic equator where the earth's 

field was overpowered by the deflecting magnet. Th e latter was moved 

further away, a trough compass was laid across the top of the instrument, 

and a small telescope was added for use on shore. With these improvements 

the instrument was rated accurate within one minute of arc, compared to 

ten minutes for the unmodified instrument. Lloyd-Creak instruments were 

used on the Coast Survey ships Patterson, Bache, and Explorer, and on the 

Carnegie Institution's Galilee. This particular instrument was used in Newfoundland and Greenland in 1907-1908 , and remained in use until 1911. 

[Reference: CIW, Land Magnetic Observations, volume 1, pages 46, 47.] 
NUMBER 48 79 

FIGURE 66.—Magnetic observations at sea, aboard the ship Bache off Puerto 

Rico, 1904. Th e dip circle in use is similar to the Lloyd-Creak instrument 

in the present collection (No. 37, Figure 65). 
80 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 67.—No. 41 , Dip Circle, Hotchkiss, 1929. 

Patented in 1929, by W.O. Hotchkiss, later President of the Michigan 

C^ollege of Mining, this instrument was intended to improve on the standard 

dip circle, particularly as regards .sensitivity, for the use of mineral prospectors and economic geologists. 

Like the Lloyd instrument (Figure 18) and that of Schmidt (No. 21 , 

Figure 51), this one depends upon balancing the force of gravity against 

magnetic force. A magnetized needle turns on a horizontal steel axel in the 

magnetic meridian. Fastened to the magnet is a counter-arm carrying a 

movable weight. In use, the relative angular positions of these elements 

enables the user to calculate the total magnetic intensity. 

[References: J.A. Fleming, Terrestrial Magnetism and Electricity. N.Y.: 

McGraw Hill, 1939, page 127. Noel H. Stearn, "Practical geomagnetic 

exploration with the Hotchkiss superdip," reprint, without source identification, in the museum's Division of Physical Sciences.] 
NUMBER 48 

FIGURE 68.—Nos. 42, 43, 44, Prospector's Dipping Needles. 

These are commercial instruments sold in the United States. Th e W. Sc 

L. E. Gurley instrument on the right (No. 42) may be from the late 19th 

century, as may that on the left (No. 44), made by Keuffel & Essor, and 

used by Charles Batchelor (1845-1910), an early associate of Edison in the 

installation of electric power systems. Th e instrument in the center (No. 

43), made by the Eugene Dietzgen Co., is from the twentieth century. 

Their catalogue for 1902-1903 lists this at twelve dollars. 
82 

SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

h^^*!^_a^ 
NUMBER 48 83 

FIGURE 69 (facing page, top).—Nos. 45, 46, Dip Circles. 

These instruments, more elaborate than those shown in Figure 68, 

appear to be for classroom demonstration. Th e instrument on the left (no. 

46) was made by Queen of Philadelphia. Tha t on the right (no. 45) is 

unmarked. It carries, on the same axis as the (cylindrical) magnet, a needle 

which can be set at various points on a scaled sector. Both instruments were 

probably made in the 20th century. 

FIGURE 70 (facing page, bottom).—No. 47, Earth Inductor, Marine, CIW, 

1912. 

Marine earth inductors represented a major advance in instrumentation, 

both in terms of accuracy and ease of use. This one was developed at the 

DTM and was installed on the non-magnetic ship, Carnegie. Th e coil is 3 

in/7.6 cm in diameter. It proved to be so superior to the Lloyd-Creak dip 

circles that it continued in use on cruises two through five of the ship, 

circumnavigating the globe several times. It was also used as the standard 

inclinometer at Carnegie shore stations. Th e galvanometer shown with it is 

the type used for land observation. At sea it was used with an Eintoven 

string galvanometer. 

[Reference: CIW, Ocean Magnetic and Electrical Observations 1915-21. 

(Washington, 1922, pages 24ff ] FIGURE 71.—NO . 48, Earth Inductor, CS 8, ca. 1950. 

This is the only earth inductor in the collection that was built expressly 

for permanent installation. It differs from others included herein mainly in 

its size and weight, which gave it increased stability and accuracy. Th e coil 

is 4V8 in/11.7 cm in diameter. It was built by the staff of the U.S. Naval 

Observatory instrument shop, apparently for the Coast Survey, which 

installed it at the magnetic observatory in Sitka, Alaska in 1951. 
84 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

F'iGURE 72.—Nos. 49, 50, 51 , Earth Inductors, demonstration. 

These are typical instruments for classroom demonstration. Tha t on the 

left (No. 49) was made by Jas. W. Queen of Philadelphia and used at 

Franklin College, Franklin, Indiana. Th e center instrument (No. 50) was 

made by Max Kohl of Chemnitz, Germany, and used at Trinity College, 

Hartford, Connecticut. Th e right-hand instrument (No. 51) used at Princeton University, is unmarked and probably the only one of the three made 

in the 19th century. 

FIGURE 73 (facing page).—No. 54, Induction Apparatus, Lamont. 

This apparatus, for the calibration of magnetometers, is shown here (to 

the left) mounted on a magnetometer. When a magnet is placed in a 

magnetic field, such as that of the earth, its magnetic moment is increased 

or decreased temporarily by magnetic induction in an amount that is 

proportional to that component of the field directed parallel to the magnetic 

axis of the magnet. Th e ratio of the change produced by unit-field to the 

original magnetic moment of the magnet is called the induction-coefficient 

of the magnet. Shown here is apparatus developed by Lamont for its 

measurement, although this example dates from the early 20th century. 

T h e instrument is of brass, 18.5 in/47 cm. long. 
NUMBER 48 85 

NUMBER 48 87 

FIGURE 74 (facing page).—No. 55, Nelson Magnetic Induction Apparatus. 

This apparatus, developed by J.H. Nelson in 1938, is shown with the 

Coast Survey's India Survey pattern magnetometer (No. 21 , Figure 50). It 

was used at the U.S. "Standards Observatory" at Cheltenham, Md. Like the 

Lamont apparatus (No. 54, Figure 73), which it replaced, its purpose is to 

measure the "induction-coefficient." Whereas the Lamont apparatus relied 

on conventional permanent magnets to produce an auxiliary field, in 

Nelson's apparatus a precisely regulated current is passed through the 

hanging coils (9 in/23 cm long) creating a weak magnetic field. 

FIGURE 75.—No. 56, Model of Terrestrial Magnetic Plot, 1862. 

This plaster model represents in three dimensions the variation of 

declination with the hour of the day and the month of the year, on the 

basis of data collected by A.D. Bache from 1840 to 1845 in Pennsylvania. 

T h e elevated areas, as at 13 hours through all the months, indicate periods 

when the needle pointed west of the average position—the average position 

being indicated by the circle in the lower left and the curved line on the 

right. Th e needle was east of this position between the hours of about 20 

and 10, as is represented by the depressions. Th e most marked daily 

variation of the needle's position is seen to have occurred in August. 

T h e model was made by Ferdinand Engel of the Coast Survey, to 

accompany Bache's report on the results of the magnetic observatory at 

Girard College, Philadelphia. 

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