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S. DILLON RIPLEY 

Secretary 

Smithsonian Institution 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY • NUMBER 10 

ROEBLING'S 

DELAWARE & HUDSON CANAL 

AQUEDUCTS 

Robert M. Vogel 

SMITHSONIAN INSTITUTION PRESS CITY OF WASHINGTON • 1971 
FIGURE 1.—The Delaware Aqueduct, 1970, in the early morning river mists. (Photograph by author.] 

COVER: The Delaware Aqueduct, 1969. (Photograph by David Plowden.) 
ROEBLING'S 

DELAWARE & HUDSON CANAL 

AQUEDUCTS 

The nineteenth-century American civil engineer, John A. Roebling, is best 

remembered for his crowning work, Brooklyn Bridge, built to his design by his 

son, Washington, following the elder Roebling's death in 1869. Although an 

engineering monument of the highest order, Brooklyn Bridge must—if historical 

justice is to be done—share its notoriety with a small, relatively obscure suspension bridge that was Roebling's second work, and is his earlist still standing. 

Moreover, in all likelihood, the Delaware Aqueduct is the oldest existing American suspension bridge and may well be the oldest existing suspension bridge in 

the world (that retains its original principal elements). The sole survivor and 

largest of four suspension aqueducts erected by Roebling between 1847 and 

1850 to carry the Delaware & Hudson Canal over rivers, the Delaware Aqueduct stands today only because of its strategic location. Following abandonment 

of the canal in 1898, the structure was converted to a private highway bridge, 

which function it continues to serve, spanning the Delaware above Port Jervis. 

T H E AUTHOR: Robert M. Vogel is Curator of the Division of Mechanical 

and Civil Engineering in the Smithsonian Institution's National Museum of 

History and Technology. 

The Delaware & Hudson Canal 

Unlike the Erie and most other American barge 

canals, the Delaware & Hudson Canal, opened in 

1829, was built as an essentially one-way route to 

transport a single commodity — anthracite coal — 

rather than general freight in two directions.1 It was 

1

 The canal company did, of course, avail themselves of the 

opportunity to carry whatever along-the-line general freight 

presented itself, and this business, while far less significant 

than coal haulage, was a worthwhile account. For example, 

in the year 1846 the goods transported were: coal, 318,000 

tons; general merchandise, 28,000 tons; and lumber, 10 

million board feet. (Annual Report of the Board of Managers 

of the Delaware & Hudson Canal Company for the Year 

1846. New York, 30 March 1847). 

projected by Maurice and William Wurts as a means of 

exploiting their great coalfields in northeastern Pennsylvania, a canal at that time being the only feasible 

way of getting the bulk coal to the seaboard. As New 

York was potentially the most profitable market area, 

the canal was planned to strike for the Hudson River, 

down which the coal could be readily transported to 

the city. Charters were granted to the Wurts' by the 

Pennsylvania and New York legislatures to improve the 

navigation of the Lackawaxen River—reaching practically into the Lackawanna coalfields at Honesdale and 

at its mouth joining the Delaware—and to build a 

line of water communication between the Delaware 

and Hudson rivers. 

The Delaware & Hudson Canal Company was 

1 
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of Progress: History of the Delaware & Hudson Company.) 

formed and in the spring of 1823 contracted with 

Benjamin Wright to survey and locate a suitable 

route. At the time, Wright was still serving as chief 

engineer of the Erie Canal. He was instructed to select 

a line from tidewater on the Hudson at Rondout 

(near Kingston), up the valleys of the Rondout, Neversink, Delaware, and Lackawaxen rivers to the coalfields. The total distance was 108 miles with a lockage 

of 1,086 feet.2 Construction began in 1825—the year 

of the Erie's opening—with Wright acting as chief engineer and the later renowned John B. Jervis as his assistant. The entire canal was opened for business in 

October 1829. Seven thousand tons of anthracite 

passed its length during the first year. Operations 

reached their peak in 1872 when 2.9 million tons were 

2

 This figure was 1,073 feet until the final improvement in 

1875 when lock changes raised it. The difference in elevation between terminals was 343 feet. 

moved.3 From that time, competition from an expanding railway network rendered the canal obsolete 

with increasing rapidity, tonnage gradually declining 

until final cessation and abandonment in 1898.4 

Improvements and Enlargements 

When the canal was opened, it was the sole means 

for transporting coal out of the anthracite region. It 

3

 Noble Whitford in his History of the Canal System of the 

State of New York states that the peak year was 1868 with 

almost two million tons, but the higher figure and later year, 

from A Century of Progress—History of the Delaware & 

Hudson Company 1823-1923 are more likely correct. 

4

 The history of the Delaware & Hudson Canal has been 

well documented and related. The best account is Wakefield's 

extremely detailed, beautifully illustrated, and thoroughly 

enjoyable Coal Boats to Tidewater—the Story of the Delaware & Hudson Canal. See the bibliography for this and 

other works. 
NUMBER 10 

was shallow—four feet in depth—with a waterline 

width of 28 feet (soon increased to 32 feet) and a bottom width of 20 feet. The first boats held 20 tons of 

coal. With a supply assured, the use of anthracite for 

heating, iron smelting, and steam generation expanded rapidly, engendering more business for the 

mines and canal. As a result of this cycle of prosperity, 

the canal eventually reached its capacity. Even with 

the introduction of 30-ton boats, by 1841 the demand 

for coal had so increased diat the canal's limit had 

been about reached. In that year, 192,000 tons were 

carried—27 times the first year's tonnage. 

The Delaware Aqueduct was built as an integral element in an almost continuous program to increase 

the canal's capacity, therefore a brief survey of the 

various improvements will be useful for placing the 

aqueduct in its setting. The need for periodic enlargements had been assumed almost from the outset, but 

as in the construction of other pioneer American 

transportation ventures like the Baltimore & Ohio 

Railroad, the modest capital initially available and the 

uncertainty of later needs dictated that the first route 

incorporate many expediencies and compromises. 

With the profits from the first decade's operation, it 

was possible to undertake a modest enlargement of the 

canal.5 In November 1842, at the close of the boating 

season, work was begun to deepen the trench to five 

feet by dredging the bottom and building up the bank 

height with the spoil, permitting passage of 40-ton 

boats. The happy fiscal effects of the project, completed by 1844, were so pronounced that the canal 

management in 1845 began another increase—to produce a 5/2-foot depth which would pass boats of 50-

ton burden and result in an annual canal capacity of 

one half million tons. The cost of the project was 

$232,000. 

Even this enlargement was recognized as inadequate practically before completion, for not only was 

the demand for coal increasing geometrically, but the 

progress of the Erie Railroad into the Delaware Valley and toward the coal regions in die mid 1840s an0

 According to A Century of Progress the improvements 

were financed also by increased capitalization. Up to 1845 

the share capital was $1.9 million. At the end of 1847— 

to finance the major enlargement then under way—it had 

been increased to $3.9 million, and by the end of 1850 to 

$6.6 million. The net profit for the year 1850 was about 

12 percent on invested capital. 

nounced the end of the canal's monopoly of anthracite 

transportation. Consequently, the company was compelled to operate as economically as possible in order 

that its rates might be competitive with the railway's, 

if not actually lower. The only available means of reducing coal transportation costs between Honesdale 

and the Rondout depot were by increasing the capacity of the boats and reducing transit time. 

With the threat of competition from the Erie hastening them into already inevitable action, the Delaware & Hudson directors in 1846 authorized the most 

ambitious enlargement project in the canal's history. 

The plan was to increase both capacity and speed, the 

former by both further deepening—to 6 feet—and 

widening, so that boats of 98 tons could be accommodated. The annual capacity would be thus drastically 

raised to one million tons, about five times the canal's 

1842 capacity, an indication of the growing importance of both anthracite and the canal in the coal industry. The estimated cost was $1.1 million. The principal consequence of die widening was the necessity 

for rebuilding all locks and aqueducts, the former 

being enlarged from the original size of 9^2 feet by 75 

feet to 15 by 90 feet. The lock-gate design was also 

changed to permit faster locking through. 

The most significant improvement to the canal's operation, however, was to be a material reduction in 

the passage time by removal of the worst bottleneck in 

the system—the slack-water crossing of the Delaware 

between Lackawaxen, Pennsylvania, and Minisink 

Ford, New York, just above the mouth of the Lackawaxen. As capital originally had been inadequate to 

build an aqueduct for the purpose, a still pool had 

been formed by damming the Delaware, into which 

the boats were locked down on each bank. They then 

crossed the river either by momentum or hand haulage along a ferry rope strung between the banks, the 

mules being carried over separately on a small rope 

ferry. Under ideal conditions the crossing was slow 

and a serious operational snag; at worst, during high 

water in spring and fall, the passage was impossible 

and canal operations came to a halt for days at a 

time. A further hazard was conflict with the considerable traffic of timber rafts on the river. The raftsmen, forced to traverse the low canal dam either by 

shooting it on the flowage over the crest or passing 

through a sluiceway, in general were understandably 

hostile to the canal interests and constantly engaged 

[Text continues on page 6] 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

DEVELOPMENT OF THE SUSPENSION AQUEDUCT DESIGN—PITTSBURGH 

The design employed by Roebling for all four Delaware & Hudson Canal aqueducts sprang forth fully 

developed in his first suspension structure, a 7-span 

aqueduct erected in 1844-1845 to carry the Pennsylvania State Canal over the Allegheny River at Pittsburgh. The executed plan, however, evolved only after 

passing through a number of design stages. 

(Drawings courtesy Rensselaer Polytechnic Institute.) 

FIGURE 3.—As a means of achieving watertightness, Roebling in all early schemes proposed to form the aqueduct trunk of wroughtiron plate, a rational choice in a city already 

a major iron center. By supporting the suspended structure at its extreme width, the floor 

beams acted as simply supported beams of considerable length—about 29 feet—with the great 

load of water bearing at their centers. The 

beams had thus to be of inordinate depth. 

Roebling obtained this by building up a 40-inch 

beam from a 16- and two 15-inch sticks, 

blocked apart by the longitudinal stringers. 

FIGURE 4.—Here the floor beams have been 

further stiffened by deepening to 46 inches and 

the addition of diagonal struts to transfer the 

trunk load more directly to the suspension 

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NUMBER 10 

FIGURE 5.—In this design the floor-beam members were sprung into a simpler doublebowstring form of 36-inch depth. While somewhat less stiff than the previous plans, the 

longitudinal spacing of the frames was almost halved, from 7 feet to 3 feet 10 inches, producing greater overall strength. Roebling's predilection for the Egyptian Revival, ultimately 

manifested so strikingly in the magnificent stone towers of his Niagara Bridge (Figure 25), 

was first seen in several of the Pittsburgh preliminary designs. He estimated weights and 

costs for rendering in both marble and cast iron what he termed the "pyramids." 

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FIGURE 6.—The design finally developed and accepted as 

" part of the agreement of 28 August 1844 ." bore 

but tenuous resemblance to its predecessors. The principal 

change and improvement was moving the trunk system's 

points of suspension in from the outer ends of the floor 

beams to points just outside the trunk sides, effectively 

reducing the bearing length of the beams from 28 feet to 

18, and increasing their load-supporting capacity about two 

and a half times. Moreover, they then acted as continuous beams. The weight of the towpaths and bracing, 

and the pressure of the water against the trunk sides acting 

through the inside diagonal struts, all bore downward on the 

cantilevered outer ends of the floor beams, materially 

counteracting the stress imposed by the water load at the 

center and further lowering the total stress in the beams. 

These transverse beams were finally reduced to pairs of 

6 x 16s, spaced every four feet. The iron-plate trunk and the 

architecturally elaborated pyramids of iron or marble were 

casualties, presumably victims of harsh fiscal policy; but 

the double-diagonal wood-plank trunk sides and floor that 

replaced the iron added enormously to the vertical and 

lateral stiffness of the spans, and if cheaper, were certainly 

also better. 

All elements of the Pittsburgh Aqueduc t were proportioned an d disposed to perform economically as 

well as effectively, resulting in a design of high 

efficiency. I n the Delawar e & Hudso n spans thre e 

years later, Roebling found it unnecessary to mak e any 

appreciable modification of the plan. Th e Pittsburgh 

Aqueduc t served well until abandonmen t of the canal 

in 1860, following which it was removed. 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

// 

FIGURE 7.—R. F. Lord's plan for re-routing the canal at Lackawaxen in conjunction with an 

aqueduct crossing of the Delaware. Rough sketch sent to John A. Roebling 27 February 1847. 

(Courtesy of Rensselaer Polytechnic Institute.) 

[Text continued from page 3] 

the company in physical and legal harassment. An aqueduct had, in fact, been projected from the canal's 

beginning. The need now being pressing and the capital available, it was included in the enlargement plan. 

Construction of the Delaware Aqueduct 

R. F. Lord, chief engineer of the canal, in planning 

the enlargement relocated the canal route at Lackawaxen, establishing the aqueduct over the Delaware 

not above the mouth of the Lackawaxen River at the 

rope ferry site, but just below. This necessitated, in 

addition, construction of a second new aqueduct—over 

the Lackawaxen (Figures 7 and 8). Every Delaware 

& Hudson Canal scholar and author has speculated 

on Lord's reasons for planning the new route in that 

seemingly extravagant way, without having drawn any 

very convincing conclusions. There were obvious disadvantages to the scheme, notably the added cost of 

the second aqueduct and the fact that the piers of the 

Delaware Aqueduct would be subject to the collective 

flow and battering of ice from both rivers. Two reasons are most commonly assumed for the re-routing: 

political considerations; and riverbed and riverbank 

conditions unfavorable to the upstream location. The 

first, in the case of a private company under the scrutiny of its stockholders, seems unlikely, and there is 

nothing in the topography of the site lending much 

support to the second. More reasonable is a recent be-
NUMBER 10 

YOR K 

P E N 

FIGURE 8.—The canal at Lackawaxen, about 1860, showing both the old canal and the newroute across the ''flats" between the new aqueducts. (Courtesy of Manville B. Wakefield, from 

Coal Boats to Tidewater.) 

lief of Manville B. Wakefield, author of the definitive 

Delaware & Hudson Canal history, that if the aqueduct had been built at the ferry, practically opposite 

the Lackawaxen's mouth, the piers would have been 

in constant jeopardy from the great ice floes that annually came down the Lackawaxen, grinding across 

the Delaware to the eastern shore with great force. 

Damage from these floes necessitated practically 

yearly repairs to the lock and bank of the canal which 

had been there before the aqueducts. 

Another likelihood, however, is suggested by the site 

conditions. Had the ferry location been selected, the 

aqueduct would have been right in the slack-water 

pool, with several consequences. First, there would 

have been less vertical clearance under the aqueduct 

for the rafts, probably an insufficient amount at spring 

high water when much of the rafting was done. 

Worse, the cofferdams used in building the aqueduct 

piers would have to have been considerably higher 

and heavier, and the entire problem of pier construction would have been a good deal more difficult in the 

deeper water of the dammed pool, quite possibly to a 

degree more than offsetting the added cost of the 

Lackawaxen Aqueduct. There is also the probability 

that in the twenty years the Delaware had been stilled 

above the dam, quantities of silt had been deposited in 

the pool so that there would have been that much 

more material to excavate before reaching a solid 

footing. Finally, the river, in addition to being deeper. 

was, on the evidence of contemporary photographs, 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

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NUMBER 10 

FIGURE 11.—The Delaware Aqueduct superstructure, February 1847. By the time of actual 

construction, Roebling had abandoned the plan to truss the floor beams as shown and had 

adopted saddle covers rectangular in cross section. Otherwise, the drawing reflects the 

aqueduct as built, and follows almost exactly the Allegheny Aqueduct design. (Courtesy of 

Rensselaer Polytechnic Institute.) 

apparently somewhat wider above the dam, which 

would have necessitated a longer structure. 

In February 1846, the canal directors authorized 

the two aqueducts at Lackawaxen, and by late December that year two proposals had been received. 

One was for a conventional, trussed, timber structure 

on masonry piers, in six spans. The other, submitted 

by John A. Roebling, a civil engineer, of Saxonburg, 

Pennsylvania, was for a wire-cable suspension aqueduct of four spans. The management inclined toward 

the latter scheme as it not only was cheaper, but more 

important, the longer spans meant two fewer river 

piers, and reduced impedance to floodwater and ice, 

as well as greater horizontal clearance for the river 

traffic. Another major advantage, not generally recognized by Delaware & Hudson historians, was that suspension spans, unlike either truss or masonry-arch 

spans, could be erected without falsework in the river, 

a matter of some significance at a site so subject to 

flooding and ice jams.6 

0

 The cables were spun in place without support. When 

they were complete and the suspenders attached, the timber 

cross frames of the trunk were hoisted into position from 

barges anchored below, following which the rest of the 

suspended structure was easily laid down. The freedom from 

falsework continues to be one of the suspension bridge's 

great advantages. See Figure 36. 
10 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

Roebling's plan was tentatively accepted on 6 January 1847. On the 29th7

 Lord arrived in Pittsburgh for 

a four-day visit to inspect a similar aqueduct built by 

Roebling in 1844-1845 to carry the Pennsylvania 

Canal over the Allegheny. 

The Allegheny Aqueduct was the first bridge of any 

kind built by Roebling, who previously had done general civil engineering—mostly railroad surveys—and 

manufactured wire ropes for haulage on the inclined 

planes of the Pennsylvania state and other canal systems. The aqueduct replaced, and was erected on the 

piers of a seven-span timber structure8 that had been 

damaged by ice. In order to have his design accepted, 

Roebling was obliged to take the construction contract 

as well, at his initial cost estimate. Completed in May 

1845, the aqueduct was a resounding success, stilling 

considerable criticism. It served until abandonment of 

the canal in 1861.9 

Lord was impressed with both the Allegheny Aqueduct and Roebling's Smithfield Street (Pittsburgh) suspension bridge built in 1845-1846 over the Monongahela. At Pittsburgh, Roebling introduced a practical 

method of constructing the cables by spinning in place 

the individual wrought-iron wires of which they were 

composed, compacting them finally into a cylindrical, 

virtually solid cable, in which each wire carried its full 

proportional load. The two continuous cables supporting the wooden canal trunk and towpaths were seven 

inches in diameter, each 1,175 feet long from anchorage to anchorage. The total weight of water in the aqueduct was 2,100 tons.10 

7

 Lord's visit has been erroneously placed in December 

1847 by all authors. This would hardly have been possible, 

firstly, because of the company's inducement to press the 

project forward with full steam, and secondly, because the 

date stone of the aqueduct reads 1847. It is unlikely either 

that the masonry would have been started before the 

formal acceptance of the Roebling design or that it could 

have been laid up in the river ice in the few weeks that 

would have remained in 1847 following a visit in December. 

Roebling's 1847 diary notes Lord's visit as 29 January— 

2 February, and Lord himself in a 15 March 1847 letter to 

Roebling refers to his return from Pittsburgh. 

8

 The spans varied from 159'-6/ 2 " to 162'-7", the average 

length being 160'-8/2" (Roebling's measurements, ink 

drawing, Rensselaer Polytechnic Institute's Roebling Collection) . 

"Joseph White and M. W. von Bernewitz, The Bridges of 

Pittsburgh; A. A. Jakkula, A History of Suspension Bridges 

in Bibliographical Form. 

10

 Ibid. 

After his inspection trip, Lord concluded that Roebling's abilities were far ahead of their time. The contract for both final design and construction of the Delaware and Lackawaxen aqueducts was given to Roebling, for a combined price of $60,400, and work 

began almost immediately. 

The contract price for the Delaware Aqueduct was 

$41,750, the Lackawaxen, $18,650. Roebling claimed 

a clear profit of $8,600. While about 14 percent of his 

actual cost, it is hardly excessive when we realize that 

his contracting profit included his engineering fee as 

well. Possibly because of their remote location, these 

structures cost considerably more, relatively, than the 

Pittsburgh aqueduct: $82 and $78 per foot versus 

$48.1:L Also, the greater the number of spans, the less 

the cost per-foot-of-length, for regardless of the number, four anchorages were required, the cost of which 

was a considerable item in the total.12 Of Roebling's 

$24,900 price for the Neversink Aqueduct, $21,277 

was shown as representing the actual cost with an unidentified sum of $3,623 added to make the total. He 

notes, however: "Reiner Gewinn [net profit] circa 

5000," or about 25 percent. The figure for the High 

Falls span was nearly 29 percent.13 

Aside from Lord's report and the natural advantages of a suspension aqueduct, a further factor no 

doubt influencing the Delaware & Hudson's selection of Roebling to build the aqueducts was their confidence in him resulting from the long and satisfactory 

use of Roebling wire ropes on the inclined planes of 

the company's gravity railroad at the west end of the 

canal. 

Roebling's construction contract covered only the 

superstructure or suspended spans, "including all iron, 

timber and wire work, the company to do all masonry 

and cement."14 His presentation and estimating drawings were apparently based on only general site information, for, shortly after his return from Pittsburgh, 

Lord sent Roebling detailed data on the bank and riverbed conditions for preparing the working drawings 

(Figures 8 and 9). With these in hand, Lord's crews 

in March 1847, despite the dual handicaps of weather 

and probably river ice, commenced the foundation 

11

 Roebling, Notes (326), page 76. 

12

 See also Appendix II. 

10

 Never Sink Aquaduct High Falls Aquaduct 

1848 John A. Roebling. 

14

 Roebling, 1847 Diary, 29 January. 

Oct. 
NUMBER 10 11 

FIGURE 12.—At a time when public works wrought less havoc to the landscape than today, 

engineering structures could frequently be appreciated for their visual as well as their 

technical contribution, even in an area as scenically hallowed as the upper Delaware Valley. 

A contemporary view of the Delaware Aqueduct from William Cullen Bryant's Picturesque 

America, volume 2. 

work and the laying of the pier and abutment masonry. Although the canal company was primarily responsible for that portion of the work, continual and 

careful coordination with Roebling—who spent most 

of this period at home—was necessary concerning the 

setting of the great iron anchor plates in the abutments. These huge castings resisted the pull of the 

chains of eyebar links that rose up through the masonry mass ultimately to restrain the main cables. 

Roebling presumably visited the site periodically, 

but much of the consultation was conducted through 

correspondence. In late March, Lord advised him that 

"We are proposing to get the abutments for Delaware 

Aqueduct in a state of forwardness so that the anchors 

may be put down soon after 1st of July; and have the 

piers all done so that you can have a chance to commence the superstructure in the fall and pursue it during the winter." The substructure work on the Lackawaxen span lagged somewhat behind and Lord anticipated that the last of the four anchor plates there 

could not be placed until well into the winter, 

". . . probably by building a roof over it [the abutment foundation] so that we can use a fire, hot water 

&c."1B That excavation and masonry work could be 

carried on during that period, at that season, in that 

notoriously cruel climate, was something of a small 

1SR. F. Lord to John A. Roebling, 22 March 1847, in the 

Rensselaer Polytechnic Institute's Roebling Collection. 

miracle, and a sure reflection of the company's anxiety to capitalize on the improvement. 

Roebling took up his work at Lackawaxen probably 

in the summer or fall of 1847, working on both 

aqueducts simultaneously throughout 1848. They were 

completed by about year's end in time for the opening 

of the 1849 canal season on 26 April. The aqueducts 

were, needless to say, an unqualified success structurally and operationally. The Lackawaxen Aqueduct, 

about half a mile west of the Delaware, was almost 

identical but had only two spans, each of slightly less 

than 115 feet, with a single river pier. 

The aqueducts were designed, like the locks, to pass 

only a single boat, but nevertheless had a path on 

each side. Closely following the design used by Roebling at Pittsburgh, these aqueducts had a heavy wood 

trunk or flume holding between 6 and 6I/2 feet of 

water, 19 feet wide at the waterline. The trunk sides 

were built up of two thicknesses of 2/2 -inch, untreated, white-pine plank, laid tight on opposite diagonals and caulked up to the waterline, in effect forming a rigid, solid-lattice truss, but without functional 

top and bottom chords (Figure 11). The stiffness of 

these great trusses was such that they were capable of 

sustaining their own deadweight, leaving the cables to 

carry only the water load. The floor was also of double plank, carried by transverse double floor beams, 

[Text continues on page 15] 
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FIGURE 13 

T H E DELAWARE AQUEDUCT SUSPENDER SYSTEM 

All ironwork in the present suspender system is 

original. Unlike the plan adopted by Roebling for the 

Niagara and later bridges where wire-rope suspenders 

were hung from clamps bolted tightly around the 

unwrapped main cables, on the Delaware & Hudson 

aqueducts he first wrapped the cables for their entire 

length between the tower saddles and hung the 

doubled rod suspenders from small cast-iron saddles 

that simply sat on the cables. The scheme had the 

advantage of avoiding the many joints where the 

wrapping was interrupted at the suspender clamps, a 

problem in the later system (and today). 

It was necessary, however, to prevent the saddles 

near the towers, where the cable slope was greatest, 

from sliding downhill by a series of restraining links 

engaging the saddles in a series. Adhesion was adequate to hold the saddles in place near the center of 

the cable span. 

The long iron bushings between the suspender nuts 

and the bearing castings are recent, placed to compensate for the reduced thickness of the present deck 

system. (Drawings, courtesy of Rensselaer Polytechnic 

Institute; photographs, June 1969, by the author, for 

the Historic American Engineering Record and the 

Smithsonian Institution.) 

FIGURE 15. 

FIGURE 14 

FIGURES 15 and 17.—Roebling's pattern drawings for the 

restrained and unrestrained suspender saddles. 
NUMBER 1 0 

FIGURE 16 

•^^s w . -//j? e*/ /Ais 

r\y\ 

*•/•' "Nit 

FIGURE 17 FIGURE 18 
14 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 19.—Roebling's sketch plan for the wire shed at Lackawaxen. The coils of cable 

wire as received were placed on the front reels (A). The wire was drawn through the pins 

in the straightening blocks (B) by being wound upon the drawing drums (C), and finally 

reeled on the back drums (D). These were taken to the bridge site for spinning. Here, the 

wire was also given an initial coating of protective oil. (Courtesy of Rensselaer Polytechnic 

Institute.) 
NUMBER 10 15 

[Text continued from page 11] 

in turn hung from the suspenders as in a conventional 

suspension bridge. The 8-foot towpaths were bracketed out from the sides, level with the trunk top. 

All was supported by the continuous main cables, 

one on each side of the trunk, at the bottom of their 

dip slightly above floor level. The cables rise to be 

carried at each pier and the abutments over cast-iron 

saddles mounted on squat stone towers that stand 

about four feet above the trunk top. The suspenders 

are plain 1 % -inch-round, wrought-iron rods, doubled 

over the cables into stirrup form, the bottom ends 

threaded for the floor-beam nuts.16 They bear upon 

the cables on small cast-iron saddles; those nearest the 

towers, where the cable slope is greatest, are prevented 

from sliding downhill by wrought-iron restraining 

links or stays (Figures 13-18). 

In his account of the Delaware Aqueduct, David 

Steinman states that on this project Roebling for the 

first time used wire-rope suspenders or hangers (between cables and floor beams), an error which has 

been repeated by others. Although Roebling was indeed a manufacturer and avid proponent of wire 

rope, he did not employ it here. Its main uses, then as 

now, were in either running applications (elevators, 

hoists) or as standing (stationary) rope, where it enjoys the advantages over simple iron or steel rod of 

being more manageable in transport and erection, and 

considerably stronger. In the aqueduct(s), however, 

the hanger lengths being relatively short—a maximum 

of about 14 feet (when doubled)—handling would 

have been no problem, and the hanger spacing, dictated by the floor-beam spacing, was sufficiently 

close that the hanger loads were readily borne by 

simple wrought-iron rods at each point. Round bar 

stock was by then widely produced, and would have 

been far cheaper than wire rope. Wire rope is used for 

bridge suspenders today (and was by Roebling in later 

spans) when they are of great length and under stress 

greater than can be carried by simple rods of reasonable diameter. Neither condition being present in the 

aqueduct structures, there is no reason to suppose that 

Roebling would have incurred the added expense of 

wire rope. Furthermore, the nuts at the hanger bottoms are square and relatively thin, an early pattern 

suggesting that they are original, and all original aqueduct drawings show doubled rods over small saddles 

exactly as present today (Figures 13-18). Washington 

A. Roebling in his Rensselaer Polytechnic Institute 

thesis, "Design for a Suspension Aqueduct," (Figure 

56) specified wire-rope suspenders, which may have 

been the source of Steinman's confusion. Even more 

likely, however, is a small drawing found recently in 

the Rensselaer Polytechnic Institute Roebling Collection. Although at one time in a folder on the Delaware Aqueduct, it is undated and unmarked as to project. It shows a wire-rope-suspender end socket. Notes 

refer to "upper" and "lower" suspenders, and the attachment of the suspenders to the main cables with 

"clamps," conditions not found at Lackawaxen, but 

definitely so at Roebling's Niagara railroad bridge of 

1851-1855, where the upper and the lower decks 

hung from separate sets of suspenders that were of 

wire rope. The drawing apparently found its way into 

the wrong folder at some past time. 

Roebling had also developed at Pittsburgh the 

method used to fabricate the cables and anchor them 

at their ends. It was used in every bridge he built 

(except the Smithfield Street), and has been used for 

major suspension bridges by most of his successors to 

the present day.

 17

 The 2,150 iron wires forming each 

of the Delaware Aqueduct's 8l/2-inch cables were individually spun in place. Each cable is composed of 

seven strands.18 In his Notes, Robeling specified varying numbers of wires in the strands: 

First strand 

Second strand 

Third or center strand 

Fourth strand 

Fifth strand 

Sixth strand 

Seventh strand 

Total 

270 wires 

270 wires 

320 wires 

320 wires 

320 wires 

325 wires 

325 wires 

2,150 wires 

The compacted diameter of the cables without outer 

wrapping was 8.36 inches, "intended to be 8y2 

inches." The weight per foot, without wrapping was 

"David B. Steinman, The Builders of the BridgeStory of John Roebling and His Son, pages 101-105. 

-The 

17

 Roebling patented the system after its successful application on the Pittsburgh Aqueduct (United States Patent 4945, 

26 January 1847), Apparatus for Passing Suspension Wires 

for Bridges Across Rivers, &c. 

18

 Roebling, Notes (326). 
16 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

122.74 pounds, and the total length of each cable, 576 

feet. Each strand was formed by carrying the wires 

across from anchorage to anchorage, over the saddles, 

in a bight of two wires at a time carried by a traveling 

sheave, so that at each anchorage a loop was formed 

which passed over a cast-iron strand shoe, pinned to 

the anchor bars, anchoring the strand. The strands are 

thus actually skeins formed of a single, continuous 

wire, spliced at the ends.19 Between the towers the 

seven strands were compacted into cylindrical form, 

virtually solid, then varnished and served with a continuous wrapping of iron wire for protection from the 

weather. Where they splay out between the abutment 

towers and the anchor bars, however, the strand loops 

are exposed to view, clearly showing their formation 

as they join the strand shoes (Figures 20—23). Although photographs of the aqueducts in use show wood 

guards over these sections, the loops would still have 

been subject to a certain amount of condensation and 

other moisture. The exposure to the weather of so 

much area of such small-diameter strands, without 

wrapping, is in odd discord with Roebling's consistent 

advocacy of solid, single cables, with the interior wires 

protected overall by the envelopment of a close wrapping. It was, in fact, on this very point that he inveighed most critically against Charles Ellet, a contemporary and sometimes rival suspension-bridge 

builder, and other members of his school. Ellet favored, rather, cables composed of many small, separate wire bundles, because, he claimed, with a solid, 

wrapped cable it was impossible to so spin the individual wires that each carried its proportional share of 

the total load. Unwilling to encase any wires in masonry because of the difficulty in achieving the positive 

airtight seal needed to prevent corrosion, and aware 

that the stress on these back-span sections was less 

than on those carrying the suspenders, Roebling seems 

to have been satisfied to depend for weather protec19

 At that early stage in its history, Roebling's wire-rope 

firm was not yet drawing its own wire (in fact, was not for 

another year to move to Trenton, its eventual seat, where 

it ultimately grew into a major industrial enterprise). The 

wire for the bridge cables, as for general wire-rope production, 

was purchased from the few United States drawers and from 

importers of European wire. Roebling drew on at least three 

firms for the great quantities needed in the two aqueducts at 

Lackawaxen, the bulk of the wire being received in the first 

nine months of 1848 while the cable spinning was in 

progress. 

tion upon the varnish and oil coating of the individual 

wires and on a heavy coating of the completed 

loops. 

Tests made on samples of the cable wire removed 

from the High Falls Aqueduct, when it was finally dismantled in 1921, were reported by H. C. Boynton, a 

metallurgist at John A. Roebling's Sons Company.20 

The ultimate tensile strength was 94,166 pounds per 

square inch, well above Robeling's design requirement 

of 90,000. The condition of the wire at the time was 

described as slightly pitted but generally good, despite 

long exposure. Almost fifty years of additional exposure, without any protection, has taken its toll, for 

specimens recently gathered—surviving no doubt because of the site's remoteness—are badly pitted and 

unable to stand the bending test specified by Roebling 

for acceptability of wire. 

Another of Roebling's principal reasons for favoring 

the solid wire cable was that it added considerably to 

the overall stiffness of the suspended structure in its 

resistance to the dangerous oscillations caused by gusting winds under certain conditions. Here again, this 

effect would have been of no consequence in the aqueducts' short, unloaded back spans between the end 

towers and anchorages, where there were no suspenders. 

The anchor bars were carried down through the anchorage masonry, terminating in six-foot-square castiron anchor plates upon which the masonry bears, its 

dead weight resisting the pull of the cables. Roebling 

calculated the ultimate strength of the pair of cables 

at 3,870 tons and the stress on them (and thus on the 

anchors) from the loaded trunk at 770 tons. 

While Roebling would not embed cable wires in 

masonry, he made a practice of doing so with his 

anchor bars, from the Pittsburgh Aqueduct on. By 

pouring a thin cement grout around the bars he felt 

confident of completely excluding air and moisture, 

assuring total freedom from corrosion. When the 

Pittsburgh Aqueduct was taken down in 1861, seventeen years after its abutments had been laid up, Roebling made a careful examination of all the iron in the 

structure. "The cement was solid to the iron, no trace 

of Rust."21 

20

 H. C. Boynton, "Bridge Wire Tested After 75 Years," 

The Iron Age, volume 121 (9 February 1928), page 400. 

21 Notes on Suspension Bridges 1860 (271). 
NUMBER 10 17 

The difference in the four span lengths of the aqueduct has been a matter of occasional speculation. The 

span lengths, from the Pennsylvania to the New York 

sides, are: 

By the original Shown by Roebling as As measured, 

design built, in "Notes" (326) August 1969 

142'-0" 

131'-0" 

131'-0" 

131'-O* 

141 '-9" 

131'-0" 

131'-0* 

131'-5" 

141'-5" 

131'-4" 

130'-10" 

131'-6" 

535'-0" 535'-2" 535M " 

The three spans closest to the New York shore are 

all so close to 131 feet that the present differences are 

obviously the result only of construction discrepancies 

and the shiftings of age and long service. The original 

design did indeed call for equal lengths of 13T-0". But 

what of the odd 142-foot length of the first Pennsylvania span? That, too, is specified as early as 27 February 1847 in Lord's rough sketch (Figure 9), which 

is the earliest mention found on the subject of the aqueduct's relationship to the site. The correspondence 

between them does not make it clear whether Roebling or Lord made the basic determination of the 

span lengths. Undoubtedly they conferred during the 

Pittsburgh visit and perhaps reached a joint conclusion. That, however, does not answer the initial question. Although Lord obviously had far greater knowledge of the site conditions, his sketch shows a relatively level riverbed, with no particular circumstances 

on the Pennsylvania side that would have led to a 

span variation there. In a (presumably) later refined 

sectional drawing of the river and masonry (Figure 

10), however, Roebling clearly does show a slight rise 

in the surface of the river bottom at the first Pennsylvania pier, and it was probably to take advantage of 

the shallower water at that point that the pier was 

placed there. Had the adjacent abutment been located 

farther out into the stream to make that span also 131 

feet, it would have projected so far beyond the bank 

as to form an impediment to the flow of river and 

ice during high water. 

The Other Aqueducts 

In addition to the two aqueducts at Lackawaxen, 

the overall widening of the canal necessitated the replacement of two existing major aqueducts, over the 

Neversink at Cuddebackville and over Rondout 

Creek at High Falls near the canal's eastern terminus, 

both in New York. Both were part of the original construction, the Neversink Aqueduct a two-span timber 

truss designed by Jervis,22 and the High Falls Aqueduct—the only one referred to by its place name rather 

than the stream-crossing name—a two-span, stonearch structure. 

From the time of his arrival at Lackawaxen, if not 

earlier, Roebling was considering that aspect of the 

improvement project and, by 28 December 1847, with 

his work on the first two aqueducts barely under way, 

he submitted the following proposals to Lord for the 

replacement structures : 

Never Sink Aquaduct one span of 170 

ft in the clear, diameter of cables 95A\ 

inch, all stonework and rock excav 

to be done by Cy, myself to do all wood 

& iron work $25,000 

Never Sink 2 spans of 90 ft each in the 

clear Cables 6% inch $18,000 

High Falls one span 120 ft in the clear 

Cables 75/8 " $16,50023 

Although both structures were to have the same 

trunk dimensions and follow the general plan of the 

two Lackawaxen aqueducts, two major differences 

were proposed. The Neversink River at the aqueduct 

site could be reduced to no less than 170 feet between 

abutments. A single span would thus have been appreciably longer than even the 142-foot-long span of the 

Delaware Aqueduct, Roebling's longest to date except 

for the lighter Pittsburgh spans. He thus made the 

dual proposal for the crossing in both one and two 

spans, but strongly recommended the latter as 

cheaper, for even the added cost of the center pier 

would not have approached the $7,000 difference between the two schemes. In fact, he maintained that 

because of the greatly reduced mass of the anchorage 

masonry on both banks, even with the center pier the 

total masonry cost would not exceed that for the single-span plan, and might possibly be less.24

 (See Appendix V on page 42.) 

[Text continues on page 23] 

22 Malcolm A. Booth, "Roebling's Sixth Bridge, 'Neversink'," The Journal of the Rutgers University Library, 

volume 30, number 1 (December 1966), page 13. 

23 Suspension Aquaducts . . . Febr. 1847. 

M

 Ibid. 
18 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

T H E DELAWARE AQUEDUCT ANCHORAGES, CABLE CONNECTIONS , AND SADDLES 

The method employed by Roebling to anchor the 

suspension cables at their ends and resist the great 

stress imposed by them on the anchorage system was 

in general based upon European practice, but with two 

significant improvements. The principal of these was 

the solid encasement of the iron anchor chains in 

cement grout to exclude air and moisture and thus 

prevent rusting. European engineers traditionally left 

open galleries around the chains and anchor plates 

to permit air circulation and, more importantly, inspection and painting. The soundness of the Roebling 

plan is reflected in the top anchor link at High Falls, 

thoroughly intact after being embedded in the masonry 

for at least seventy years. (Figure 37). 

The other departure was placement of a solid timber 

grillage between the anchor plates and the superincumbent masonry mass, to act as a slight cushion between them and evenly distribute the stress between 

the two unyielding surfaces. Roebling patented the 

system after applying it on both Pittsburgh structures 

(United States Patent 4710, 26 August 1846). The 

timber, well below the water table, was not susceptible 

to rot. 

The radial thrust of the chains, as they change angle 

from vertical at the anchor plates to the back span 

angle, is borne by a series of stone blocks set into 

the abutment side walls. The projection of these 

is seen in Figure 21, and in the ruins of the Neversink 

Aqueduct south anchorage in Figure 39. (See also 

Figure 46.) 

Equal stress in all the anchor chain links in a section 

was obtained by drilling their eyes simultaneously, in a 

pile, to ensure equal length. (Drawing, courtesy of 

Rensselaer Polytechnic Institute; photographs, June 

and November 1969 for the Historic American Engineering Record and the Smithsonian Institution.) 

FIGURE 20.—The Pennsylvania towers 

and saddles. Remarkable survivals are 

the guides that prevented snagging of 

the canalboat tow ropes as they passed 

over: the iron bar just above the backspan strand loops and the casting bolted 

to the tower corner on the river face. 

FIGURE 21.—The New York south anchorage, showing projection of the stone 

blocks supporting the knuckles of the 

curving anchor chain. 
NUMBER 10 19 

FIGURES 22 and 23.—Saddle, strand loops, and attachment of loops to anchor chains, Pennsylvania north anchorage. 

•«**dvi*^7 

<?-.,* /<„»•„.. . 

= S4 +* * 4~* 'f\?= JJS/t. „~,X/ 

a.»~/~. 

tt~*(-*a 

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~*f* /^. 

M ( i^«« 

. . „ <ff 

. ./.,<*.-

,-<-<•;*. 

c «v«.^& 

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ifS-S*-^. 

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-, f2 .6*S-ii-jt: 

AK/i^.A: 

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FIGURE 24. 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 25.—A nearly full view of the anchor-chain and 

bearing-block system used by Roebling in all of his bridges, 

early and late, great and small, was provided in 1878 

during replacement of some of the links of the Niagara 

Railway Suspension Bridge (1851-55). Despite cement 

grouting, leakage along the chains had caused some rusting. 

Shortly after the bridge's construction, Roebling found that 

the lime he had theretofore customarily used in the grout 

to cause a bond of calcification between the masonry and 

the links in the event that there was any leakage, would in 

time cause the hardened grout to slightly shrink away from 

the iron, actually leading to leakage. After 1860 he used 

plain cement grout only. (Photograph from Modjeski & 

Masters, engineers, in the Division of Mechanical and Civil 

Engineering, National Museum of History and Technology. ) 
FIGURE 26.—Roebling's system of cable anchorage introduced at Pittsburgh and fully 

developed on the Delaware & Hudson aqueducts required no essential modification when 

thirty years later it was applied to a structure on the scale of the Brooklyn Bridge. Compare 

the details of anchor bars, shoes, and strand loops with those used at Lackawaxen (Figures 

22 and 23). At Newr York, however, these elements were fully protected from exposure by 

masonry coverings. Behind the eyebars is the cable-wire spinning wheel. (From a lantern 

slide, Brooklyn anchorage, about 1877, in the Division of Mechanical and Civil Engineering, 

National Museum of History and Technology.) 

FIGURE 27.—Delaware Aqueduct from above the mouth of the Lackawaxen, shortly before 

suspension of canal operations. The Delaware & Hudson dam, retained after construction 

of the aqueduct to provide feed water for the section of the canal to the east, is just in front 

of the aqueduct piers. (Photograph courtesy of the Delaware & Hudson Railway Company.) 
22 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURES 28 and 29.—The downstream side of the Delaware Aqueduct before abandonment. 

Except for the canal's absence, Lackawaxen, Pennsylvania, seen across the river, has 

changed little over the years. In the lower view may be seen the Erie Railway's truss bridge 

over the Lackawaxen, built instead of Roebling's proposed suspension span (Figure 57), 

and the remains of the 1828 canal and the canal company's dam across the Delaware. 

(Upper photograph, courtesy of Jim Shaughnessy; lower, courtesy of Delaware & Hudson 

Canal Historical Society, Ghear Collection.) 
NUMBER 10 23 

[Text continued from page 17] 

Despite the prospect of a substantial saving, the 

company for unknown reasons ultimately selected the 

single span, most likely under the impression that 

$7,000 was a cheap price for avoidance of the difficulties—such as ice floes, flood-born debris, and undermining—to be looked for with a river pier. The 

Lackawaxen River crossing offered no option, for 

there a single span would have been 230 feet in 

length. That apparently was more than Roebling 

cared to attempt at the time with loading of that 

magnitude, and there is no record that a one-span aqueduct was ever considered. 

The other suggested deviation from the earlier 

methods arose from the fact that at High Falls the 

banks were constituted of good, solid "mill stone" 

rock. Roebling proposed to embed the anchor plates 

directly in the rock, saving the cost of building up artificial masonry masses above them. Because of the native rock's supposed impermeability, he was willing to 

carry the cable wire through it, connecting the strand 

loops directly to the plates eliminating the need for 

expensive anchor chains. The plan was to excavate 

adits or channels about sixty feet long and just large 

enough to get the plates down into place. Presumably, 

they would have been too small to permit the cables to 

be conventionally spun in place as the spinning wheel, 

cable reels, and other apparatus all had to be located 

either near the ends of the cables or beyond. Roebling's solution was a modification of the plan he had 

used in his second bridge, the highway span over the 

Monongahela at Pittsburgh, where he had prefabricated the cables on shore and then hoisted them, complete, into place. At High Falls, he proposed "The 

strands to be made in the Canal, and put into boxes, 

then rolled to the abutment and across on tresselwork, 

then hoisted in the saddles."25 His suggestion that the 

strands be "made in the canal," was probably based 

upon the fact that the "boxes" could be rolled out in a 

straight line without turns from the southeast side of 

the creek. It was easier to attain equal tension in the 

wires by handling only one strand at a time than if the 

entire cable was treated as a unit. This advantage, 

however, was somewhat reduced since Roebling—be-

*?:•* TJZf.•"%_. Hk*w *£d, / / 

FIGURE 30.—One of the last boats through the canal crossing the Lackawaxen Aqueduct, about 1898, moving light 

toward Honesdale. On the Delaware and Lackawaxen aqueducts the towpath was widened around the midstream 

towers to provide a constant width; the path on the berm 

side, however, used mainly by common foot traffic, was 

not widened. (Photograph courtesy of Delaware & Hudson 

Railway Company. 

Ibid. 

cause of the relatively small cable diameter—planned 

to use only four strands rather than the customary 

seven that compact more readily into the final circular 

section of the finished cable. 

Apprehension over being able to prevent moisture 

from reaching the buried wires, the uncertainty of 

achieving equal tension in all wires of all strands, the 

problem of erecting falsework in the river, and the apparent general decision to increase the clear span of 

the aqueduct from 120 to 130 feet (ultimately 135), 

necessitating larger cables, must in combination have 

been sufficient to scuttle the scheme. On 11 November 

1848, as the aqueducts at Lackawaxen were nearly 

complete and ten months after his first proposal, Roebling submitted a second one for the replacement 

structures. It specified single spans of 160 feet clear for 

Neversink and 130 feet clear for High Falls, with 
24 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 31.—The Lackawaxen Aqueduct, looking northeast toward the Delaware. As at 

Pittsburgh, Roebling arranged the floor beams and side struts of the Delaware & Hudson 

Aqueduct trunks into simple trusses that both supported the overhanging towpaths and 

resisted the side pressure of the water on the trunk walls. (Photograph courtesy of Delaware & 

Hudson Railway Company.) 

FIGURE 32.—High Falls, New York, and the aqueduct over Rondout Creek. To the right of 

the span is the original masonry-arch aqueduct it replaced. (Photograph courtesy of Delaware 

& Hudson Railway Company.) 
NUMBER 10 25 

cables anchored by chains, for $24,900 and $20,400, 

respectively.26 

The proposal also established a schedule that called 

for the company to start their masonry work almost 

immediately, allowing Roebling to complete his superstructures by the end of 1849. The company was anxious to see the improvements brought into effect as 

soon as possible, and had accepted the proposal less 

than a month after its submission (even before knowing whether the first two aqueducts would conduct 

themselves as advertised). The company's crews, however, were employed on the canal proper until opening of the season and readmission of the water, and 

apparently it did not have the labor force to undertake its part of the projects until the spring of 1849. 

Work continued throughout 1849 and most of 1850, 

and both aqueducts went into service at the start of 

the 1851 canal season. The 9i/2 -inch cables of the 

Neversink span were the largest that had been made 

for any suspension bridge up to the time. Comparative 

data on all four aqueducts are given in Appendix I. 

Decline and Recent History 

The 1847-1850 enlargement of the canal was spectacularly successful. In the Delaware & Hudson Annual Report for 1849, the management noted that 

"The two Wire-Suspension Aqueducts over the Delaware and Lackawaxen Rivers, are a part of the new 

work brought into use last year, and prove to be all 

that was expected or can be desired of such structures, 

and a great facility to the navigation."27 With slight 

additional deepening and widening, the canal by 1852 

was able to pass 130-ton-capacity boats, which had the 

coincident advantage of being large enough to be river-worthy. They could thus make the down-Hudson 

trip to New York directly, eliminating the expensive 

transshipment of the coal to schooners at Rondout, 

with the boats being hauled up and down river by 

tugs. 

Chief engineer Lord estimated that the project, 

particularly the advent of the Delaware and Lackawaxen aqueducts, had avoided nine days stoppage of 

boating due to high water in the first year of operation, and cut a full day from the passage time. All in 

all, the company could reduce rates by half, bringing 

the transportation cost down to about fifty cents per 

28

 Never Sink Aquaduct Oct. 1848. 

27

 Annual Report, Delaware & Hudson Canal Company. 

New York 1850, p. 3. 

ton. On this basis, the canal was able to compete quite 

successfully with the railroads for bulk coal haulage 

well into the 1870s. It has been noted that the peak 

year was 1872 when almost three million tons of coal 

were carried. From that time on, the competitive situation deteriorated rapidly for the canal. Whereas it 

had by then about reached its maximum practical 

capacity, the technology of the railroad was in a state 

of flourishing and seemingly unlimited advance. In 

the last three decades of the century, locomotive 

weights doubled, with corresponding increases in car 

capacity and train lengths, and decreases in rates. 

The Delaware & Hudson management had the wisdom to march with rather than against this trend, and 

although the canal was operated almost to the century's end, it was under rapidly declining conditions as 

the company expanded its own rail network which it 

had commenced decades earlier. In 1898 the last boat 

moved over the waterway, and the following year the 

physical plant of the system was liquidated. 

Of the four suspension aqueducts only the Delaware 

had any apparent adaptive usefulness. The Lackawaxen, Neversink, and High Falls (Rondout) spans 

were all simply abondoned and sooner or later demolished; the High Falls survived derelict until 1921 and 

the Lackawaxen even longer. Abutments and remains 

of anchor chains are evident at all three sites (Figures 

34,37-39). 

The Delaware Aqueduct, however, being in a strategic location well away from any other road crossing 

of the river, was purchased privately and converted 

into a highway bridge. From the evidence of photographs, the process of adaptation was simplicity itself. 

The towpaths were sawn off, a low railing was run 

along the downstream side of the trunk floor to provide a separated pedestrian walk, a tollhouse was built 

at the New York end, some grading was done at each 

end for accommodation to the existing roads, and 

it was "Open For Business" (Figures 41-44). 

The first private owner was Charles Spruks, a 

Scranton lumber dealer who specialized in the heavy 

timbers used as supports in the area's coal mines. Because his principal timberlands were in Sullivan 

County, New York, he purchased the aqueduct primarily to afford a simple means of getting the logs 

across the Delaware to the railhead in Lackawaxen. 

The collecting of tolls from common-road traffic was 

actually a sideline.28 

28

 Information from Mr. Edward H. Huber, Scranton. 
26 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURE 33.—Neversink Aqueduct at Cuddebackville, New York, which had the longest 

single span of the Delaware & Hudson suspension aqueducts. (Photograph in the Division 

of Mechanical & Civil Engineering, National Museum of History and Technology.) 

About 1929 the bridge was purchased by the Federal Bridge Company of Washington, D.C, a toll 

bridge holding company, which operated it under the 

name of Lackawaxen Bridge Company, incorporated 

10 January 1930. In late 1930 plans were announced 

by Colonel P. K. Schuyler, Federal's president, to rebuild the floor system for "highway traffic of the 

heaviest class."29 It may have been at that time, or in 

about 1932, after a fire that destroyed the woodwork 

of the west (Pennsylvania) span and part of the one 

adjacent, that virtually all of the original timber was 

removed—trunk, floor beams, and all. The simple 

floor system of today was substituted, consisting of 

transverse floor beams hung from the suspenders, 

longitudinal stringers, and plain transverse plank 

decking. 

The Lackawaxen Bridge Company was purchased 

in March 1942 by E. H. Huber of Scranton, who presently maintains the operation. A toll of twenty-five 

29

 P. K. Schuyler, "Lackawaxen Suspension Bridge Rebuilt 

for Present-Day Use," in Engineering and Contracting, 

volume 69 (November 1930), page 421. 

cents for cars and five cents for pedestrians is charged, 

with all passage free after the collector goes home at 

night. The fabric is in generally good condition. The 

masonry, except for an understandable minor deterioration of the upstream pier faces from river ice, is 

quite perfect. The floor system is good as the planking is periodically replaced, and the cables, despite unwinding of the outer wrapping in a few areas, are 

kept painted and appear as adequate as when spun. 

The posted allowable load of six tons is almost ludicrous in view of the fact that each span originally contained about 500 tons of water plus the additional 

dead load of the trunk and towpaths. True, it was an 

evenly distributed, non-moving, non-impact load, but 

there can be little doubt that the cable system today is 

not working very hard. 

The Aqueduct's Relative Historical Status 

There is good reason to believe that the Delaware 

Aqueduct is the oldest suspension bridge standing in 

the United States today. There are only two other 

possible contenders for the distinction: the famed Essex-Merrimack bridge designed by James Finley and 

erected in 1810 over the Merrimack at Newburyport, 
NUMBER 10 27 

8 \ 

FIGURE 34.-—Remains of the Lackawaxen Aqueduct. Only the west abutment survives, the 

east abutment and the midriver pier having been entirely demolished for the conveniently 

located supply of cut stone. (Historic American Engineering Record and the Smithsonian 

Institution. 

Massachusetts (Figure 53) ; and the "Wire Bridge" 

over the Carrabassett River at New Portland in central Maine. At first glance it appears that the Finley 

bridge is clearly the oldest. In 1909, however, virtually 

the entire superstructure was replaced—the shape of 

the wood towers broadly reproduced in reinforced 

concrete; the four open-link chains replaced by four 

3^2-inch wire cables; and a new steel and timber deck 

fitted. The sole fabric remaining of the original structure is the pier masonry below deck level, so that we 

have a case not unlike that of grandfather's Original100-year-Old ax which in its long history had five new 

heads and twelve new handles. The present bridge is 

plainly not that of 1810, and only loosely resembles it 

in general form.30 

The "Wire Bridge" is a rather different case. It, 

30

 Full details of the original and reconstructed bridges 

are in Engineering News, 3 August 1911, page 129 and 

25 September 1913, pages 585-87. 

too, has undergone a certain amount of rebuilding. 

The shingle and board sheathing of the timber towers 

has been replaced, the wood deck is new, and the 

original rod suspenders and clamps have recently been 

replaced by prefabricated wire ropes with new cable 

clamps. The majority of the tower framing and the 

main cables and their anchorage hardware, however, 

are entirely original, and if we recognize in these elements the heart and soul of a suspension bridge, it is 

not unreasonable to consider that the bridge is indeed 

the actual one of original date (Figure 54). 

There is some conflict about the date, the positive 

resolution of which will require more research than 

has been done to date. Unfortunately, there was probably no more documentation generated at the time of 

the bridge's construction than there would have been 

for any other relatively small bridge, so that there is 

little expectation of any new contemporary evidence 

coming to light. Local tradition, based apparently on 

certain New Portland town-meeting minutes, main-
28 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

tains emphatically that the "Wire Bridge" was built in 

1842, using wire cables fabricated in Sheffield, England. The date appears on local roadside markers 

guiding tourists to the site, and in virtually all 

recent newspaper accounts of the bridge. Charles Ellet's wire bridge over the Schuylkill in Fairmount 

Park, Philadelphia, the first consequential wire suspension bridge in America, was built in 1842, and there 

is no technical reason why the Maine bridge could not 

also have gone up then. If it did, then it preceded the 

Delaware Aqueduct by a five-year margin and thus 

rightfully deserves the title of "The Oldest Standing." 

Several factors, however, make that date seem entirely unrealistic if not unbelievable. First, a lack of 

historical authority weakens its probability. While the 

necessary technology and a certain degree of precedent did exist, the likelihood is not great of either being 

reflected in a structure, erected by local men, in 

what even today is a relatively remote region; it is, in 

fact, almost hopelessly slim. The second factor is the 

former presence of two very similar bridges in the immediate area, in the towns of Kingfield and Strong. 

At Kingfield, cables of ordinary chain were employed; 

at Strong, wire cables, as at New Portland, were used. 

The Kingfield chain bridge is known to have been 

built in 1852-1853, the Strong wire bridge in 1856. 

(They were replaced in 1916 and 1922 respectively.) 

The striking similarity of all three spans—particularly 

in the architectural character of the shingled timberframe towers—and the presence of three suspension 

bridges within a twelve-mile circle, in an area and a 

time almost exclusively of timber truss bridges, leads 

one to look for the connection among them that obviously must exist. The Kingfield span was designed 

and built, according to apparently reliable local evidence, by Daniel Beedy of Farmington ;31

 the New 

Portland span by David Elder and Captain Charles B. 

Clark;32 and about the Strong bridge, we do not 

31

 Data on the Kingfield Bridge is from an unpublished 

typescript in the files of the Smithsonian Institution's Division 

of Mechanical and Civil Engineering, Kingfield Bridges, prepared in about 1945 by the well-known bridge historian 

Llewellyn N. Edwards of Glen Echo, Maryland. Most of Dr. 

Edwards' information is based on primary and local sources 

and is considered solid. An extract appears in his "A Brief 

Discussion of the Geology of Maine Rivers and Streams and a 

History of Six Early Maine Bridges," Paper No. 15 of the 

Maine Technology Experiment Station, University of Maine, 

Orono, October 1934, pages 28-29. 

32

 "Here's the Fine Old Suspension Bridge at New Portland, 

Me." New England Construction, May 1954, pages 62-63. 

know. Thus, there may or may not have been a 

common hand between the Strong span and either of 

the other two. In any event, what surely must have 

occurred was observation of the success and cheapness 

of the earliest of the three structures, with emulation 

by two other towns and either one or two other builders. 

Assuming that the New Portland bridge was not 

built in 1842, the question is, which of the trio was the 

first? As the Strong bridge is known to have been later 

than the Kingfield, it was either Kingfield or New 

Portland. Whichever, its erection must surely have 

been regarded by the town's authorities as a rather 

unconventional solution to their bridging problem, its 

lack of local precedent evoking some trepidation. In 

that light, it seems so probable as to approach a dead 

certainty that there would not have been room for two 

experiments at once. Thus, not the added novelty of 

wire for the cables (despite its earlier use by Roebling 

and Ellet), but rather a material of far greater familiarity having characteristics of strength not only 

known, but highly visible: chain. In other words, it is 

suggested that the Kingfield bridge of 1852-1853 was 

the progenitor. Either of the wire bridges could then 

have been the second built. Even the Strong bridge of 

1856, erected only three years later, might quite logically have been of wire. The elapse of that much time 

certified that the suspension system itself, in Kingfield's 

span, was furnishing good, safe service. More significant, Roebling's famed and widely publicized Niagara 

Railway Suspension Bridge was completed the previous year, carrying a mainline railroad on an 850-foot 

span, with wire cables. 

Based on the lack of positive evidence supporting 

the 1842 date, and on the above reasoning, it is difficult to believe that the New Portland bridge was built 

a decade before the Kingfield bridge; it is quite easy, 

however, to visualize its construction a decade after 

the Strong bridge. An entry in the New Portland 

Town Report for 1 March 1866 states that David 

Elder, agent for the bridge, was paid $3,624.97.33 The 

figure is too large for mere repairs, no matter how 

major, but is a perfectly reasonable one—considering 

the scale of the structure, the place, and the time—for 

construction of the complete bridge. L. N. Edwards 

(see footnote 31) mentions the bridge only cursorily, 

noting that it was built after the Strong bridge, although he gives no evidence for the statement. 

[Text continues on page 33] 

Ibid. 
NUMBE

R 10 

29 

FIGURES 35, 36, and 37.—Slow death at High Falls. After 

standing derelict but intact for nearly twenty years fol-

lowing abandonment of the canal, fire destroyed the aque-

duct's woodwork about 1916, leaving the cables and 

suspenders in a state not unlike that during original con-

struction, just before the first of the trunk frames had been 

hoisted into place. Today only the abutment masonry and 

portions of the anchorage eyebars remain. Even these have 

not been permitted a dignified final rest: the old-metal 

vandals have removed the stones from around most of the 

upper links and cut portions of them away. (Photograph at 

right, courtesy of Delaware & Hudson Railway Company; 

center, Delaware & Hudson Canal Historical Society, Ghear 

Collection; and bottom, Historic American Engineering 

Record and the Smithsonian Institution.) 
30 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOG 

FIGURES 38 and 39.—The masonry of both Neversink Aqueduct abutments survives, but all 

the upper sections of the anchor bars are gone. Just upstream on both sides of the Neversink 

are fragmentary remains of the predecessor two-span timber-truss aqueduct. As at High 

Falls, the canal was slightly realigned during the enlargement to permit construction of the 

new aqueduct without disrupting service on the old. On both of the later structures, the 

abutment wing walls are straight, meeting the face at an angle, unlike the earlier Delaware 

and Lackawaxen spans where the surfaces meet in a curve. (Historic American Engineering 

Record and the Smithsonian Institution.) 

WW* ' 
NUMBER 10 31 

FIGURE 40.—Delaware Aqueduct and Minisink Ford, New York, shortly after the canal's 

abandonment in late 1898. Except for removing the berm wall on the outside of the curve 

at Lackawaxen to provide road access, nothing has yet been done to alter the structure for 

toll-bridge service. (Photograph courtesy of the Delaware & Hudson Railway Company.) 

FIGURE 41.—Interior of the Delaware Aqueduct trunk after conversion to a toll bridge, about 

1900. (Photograph courtesy of the Delaware & Hudson Railway Company). 
32 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURES 42 and 43.—Early twentieth-century views of the Aqueduct from New York. (Photographs courtesy of the Delaware & Hudson Railway Company.) 
FIGURE 44.—View from Lackawaxen, about 1910. The towpaths have been removed in the 

alteration but not the tow-rope rail. During the canal period, the upstream faces of the 

piers were protected by pointed wooden ice-breakers. Renewed as needed, they prevented 

the deterioration that has occurred since. The pier faces were shelved to support the icebreaker framing. The icebreakers are seen in Figure 27. (Photograph courtesy of the Delaware & Hudson Railway Company.) 

[Text continued from page 28] 

Finally, the town-meeting minutes of about 1842 

that are purported to refer to this bridge speak of it as 

having been projected and built by a Colonel Morse; 

the structure, because of its novelty, being referred to 

locally as "Morse's Fool Bridge."34 Thoroughgoing 

local inquiry, however, reveals that neither that name, 

nor Morse's in any form, has apparently ever been attached to the bridge, while a granddaughter of Clark 

does clearly recall family lore crediting her grandfather with its construction. So it would seem that the 

1842 references are either to another, entirely different, bridge that had a short life and left no solid evidence of its existence, or to an earlier, never-built project for the same site.35

 Taken altogether there seems 

reason enough to discount the date of 1842, and consider the Delaware Aqueduct to be in fact America's 

earliest standing suspension bridge. 

Its future seems reasonably secure. Although it, too, 

is in a remote area, it is happily situated between the 

Poconos and the Catskills, and still is the only crossing 

of the Delaware for ten miles upstream and four 

downstream so that enough vacation and local traffic 

uses it to make it an economic if not wildly profitable 

venture for its owner and worth adequate maintenance expenditures. It has been recognized as a historic landmark by the state of New York, which has 

erected a roadside marker, and was recently placed on 

the National Register of Historic Landmarks, fitting 

recognition for one of the nation's most significant 

engineering relics and the earliest extant work of the 

man who is the rightfully acknowledged father of the 

modern suspension bridge. 

34

 These statements are reported in an article on the New 

Portland bridge from GRIT—Family Section, 26 December 

1965 (a Sunday magazine supplement), posted in the Hotel 

Herbert, Kingfield, Maine, noted in August 1969. 

30

 For the data in this paragraph, I am indebted to Mr. 

Charles A. Whitten, C. E., of Augusta, Maine, who has 

closely followed the career of the New Portland bridge, and 

actively pursued its early history. He shares my serious 

doubts concerning the earlier date, as do all other bridge 

historians encountered. Jakkula, in his A History of Suspension Bridges in Bibliographical Form, curiously does not list 

it although he does the Strong and the Kingfield spans, using 

as his sole reference the Edwards article (footnote 31). 
34 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

DELAWARE AQUEDUCT-DELAWARE AND HUDSON CANAL • 184-7-184-8 

THE DELAWARE AQUEDUCT IS PROBABLY THE OLDEST SUSPENSION BRIDGE IN THE U.S. 

IT WAS DESIGNED AND BUILT BY JOHN A. KOEBLING, A PIONEER Of SUSPENSION 

BRIDGE TECHNOLOGY, AFTER HIS COMPLETION OF A SIMIIA B STRUCTURE OVER 

THE ALLEGHENY IN PITTSBURGH. HE FAVORED THE SUSPENSION SYSTEM 

OVER CONVENTIONAL MASONRY ARCHS OR TIMBER TRUSSES AS THE GREATER 

PERMISSABLE SPAN LENGTHS REQUIRED FEWER RIVER PIERS , LE5SENING 

IMPEDANCE TO ICE, FLOOD WATERS AND RIVER TRAFFIC THE DELAWARE AQUEDUCT WAS THE LONGEST OF FOUR 6UILT ' DURING A MAIOB IMPROVEMENT IN 

THE CANAL AND IS THE SOLE SURVIVOR. AFTEJJ. THE CANAL WA3 ABANDONED 

IN 1698 , THE AQUEDUCT WAS DEWATERED AND CONVERTED INTO A HIGHWAY 

TOLL BRIDGE WHICH FUNCTION IT CONTINUES TO SERVE. THE WOOD TRUNK WAS 

REPLACED BY THE PRESENT DECK SYSTEM FOLLOWING A FIRE IN 1932. 

<-••" > » iHHMM^»^»^4hM^tJHMHH)-»-*l|lSlrM^ l » K.l,».H.»..X-«-,»1«„t.|t,jt..H,«.»,-)r,t-jt,«.».,IHHH|7f 

SCALE M faer 

A/. W. ELEVATION- SECT/OK 

MUWN wr LHJC i^cOVr . SJiEE 7 I or 3- 7/V/5 STffocruee 

MOHAWK-HUDSON AREA SURVEY DELAWARE AND HUDSON CANAL- DELAWARE AQUEDUCT NY 5529 

MINISINK FORD, SULLIVAN COUNTY. NEW YORK LACKAWAXEN, PIKE COUNTY, PENNSYLVANIA I 

HISTORIC AMERICAN 

BUILDINGS SURVEY 

H T 16 OF 20 aun 

FIGURE 45. 

FIGURES 45, 46, and 47 (overleaf).—The following three 

drawings were made in August 1969 by the MohawkHudson Area Survey (M-HAS), sponsored by the American Society of Civil Engineers, the National Park Service, 

the New York State Historic Trust, and the Smithsonian 

Institution. The M-HAS was the first project of the recently formed Historic American Engineering Record, 

established to prepare and preserve graphic records of 

significant American engineering monuments. 
NUMBER 1 0 35 

FIGURE 46. 
36 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
NUMBER 10 37 

T H E DELAWARE AQUEDUCT TODAY, Figures 48-52. (Photographs by David Plowden.) 

FIGURE 48.—The New York shore from Lackawaxen. 

FIGURES 49 and 50.—Traffic during most of the year is steady though light, but dwindles from January to 

March. As the only crossing of the Delaware for fifteen miles, the bridge fills a decided local need as well 

as being unique point of interest. 
38 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

FIGURES 51 and 52.—The contrasting massiveness of masonry piers and lightness of wire cables, so much the 

measure of the suspension bridge and so often extolled by poet and painter in the Brooklyn Bridge, is as fully 

marked at the aqueduct. 

FIGURES 53.—Essex-Merrimack Bridge near Newburyport, Massachusetts, before and after. 

In the 1909 "rebuilding" of the 1810 structure, the entire superstructure was replaced with a 

loose replica, leaving of the original fabric only the pier masonry below deck level. (From 

Engineering News (25 September 1913), volume 70, page 585.) 
FIGURE 54.—The "Wire Bridge," New Portland, Maine. While having undergone some 

rebuilding, the bridge is original in its principal elements and is a rare survival of an early 

suspension structure. (Photograph by David Plowden.) 

LIMBER 

WJHCTED, on THE DEL. & HUDSOJV CAKAL. 

Will be received until the 10th day of March next, for furnishing and delivering the following bill of Lumber, viz : 

St fe*t long, 

1 by 7 inches at one end, 7 by 7 at the other,—16 ft. long, 

Ah 7 by IS,—20 feet long, 

do, 2 1-3 by 10,—10 feet long, 

do. 2 by 10,—7 feet 8 indies long, 

do. 7 by 7,—12 feet long, 

do. 6 by 7,—6 feet 8 inches long, 

1,600 feet Linial Measure, 7 by 7 inches, for Bailing, 

i'l.i.nu 

8,600 

6,533 

1,600 feet Linial Meuore , 6 by 6 inches, for Bailing, 

1,400 do. 6 by 7, any length orer 20 feet, 

1,400 do. 5 by 5. do. 1,450 

I'lunk, 25 or 26 feet long, 2 1-2 inches uniformly thick, 76,680 

Flank, 14 feet 4 inches long, 2 1-2 inches uniformly thick, 76,680 

. by 10, or 2 inches by 12, either 16, 20, or 24 ft long, 22,400 

Jo 2 by 10 inches, 16 or 24 feet long, 19,200 

Total Board Mci of Pii 

All the above bill to be of good sound White Pine, and work full size, free of shakes, rents or blaek knots, when counter-hewed, 

and delivered on the Pennsylvania side of the Delaware river above high water mark, between the mouth of the Lackawaxen and 

Delaware Dam (for Del, and Uud- Canal) by or lief in" the first dij of Jul v next. Payment will be made when the Lumber is delivered on the bank as above stated, and approved and accepted lo (he satisfaction of the Knginecr on Delaware and Hudson Canal 

for the time being. Proposals are desired to be i » writing, stating the price per one thousand feet board measure, and directed to 

the subscriber, at the office of the Delaware and Hudson Canal Company, in llonesdale, Wayne county, Pa. For any information 

relating to the above bill of Lumber, apply to t <e Engineers or Superintendents on Delaware and Hudson Canal. 

February 23d, 1847. 

JOHN A. ROEBLING, Engineer. 

FIGURE 55.—Invitation to supply lumber for the Delaware and Lackawaxen aqueducts. 

(Courtesy of Rensselaer Polytechnic Institute.) 
I 

Summary of Delaware & Hudson Canal Improvements 

(From Whitford, Volume 1, page 1467) 

Tear of Completion 

1829 (as first built) 

1844 

1852 

1875 

Width at top 

{feet) 

28 

44 

48 

48 

Width at bottom 

{feet) 

20 

26 

30 

32 

Depth 

(feet) 

4 

5 

6 

6 

II 

Comparative Data on the Four Delaware & Hudson Aqueducts* 

Delaware Lackawaxen High Falls Neversink 

Number of spans 4 2 1 1 

Center-to-center span 

length (feet) (see page 17) 114.37 145 170 

Number of cables 2 2 2 2 

Diameter of cables 

(inches) 8V2 7+ 8V2+ 9V2 

Total number of wires 

in each cable (see 

page 15) 2150 1624 2300 2880 

Weight of cable 

per foot (pounds) 122.75 90 125.7 170 

Weight of water in one 

span at 6'-6" 

depth (tons) 489 424 538 632 

(142-foot span) 

Working tension on 

both cables (tons).-- 771 552 790 998 

Ultimate tensile 

strength of both 

cables (tons) 3870 2900 4100 5200 

Roebling's contract 

price $41,750. $18,650. $20,400. $24,900. 

Cost per foot of suspended trunk (see 

page 10) $78.00 $82.00 $141.00** $146.00** 

*Mostly from Notes (326), various pages. 

**The per-foot cost of Neversink was greater because of the larger cables and anchorage ironwork, a function of the higher price normally paid for a longer than for a shorter span. 
NUMBER 10 41 

FIGURE 56.—Suspension aqueduct design by Washington A. Roebling. See Appendix III. 

JT.9T, S. ^ ^ 

FIGURE 57.—Proposal for the New York and Erie Railroad suspension bridge at Lackawaxen. See Appendix IV. 
4 2 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

III 

Design for a Suspension Aqueduct 

This design for a suspension aqueduct is from the senior thesis of Washington 

A. Roebling (1837-1926), class of 1857, Rensselaer Polytechnic Institute. While his 

design admittedly follows closely those of his father's Delaware & Hudson aqueducts, 

Washington Roebling proposed a number of modifications, necessitated principally 

by the greater loads imposed by a 164-foot span, 40-foot trunk width, and 7-foot 

water depth. The width, the same as that of the aqueducts on the enlarged Erie 

Canal, would pass two large boats abreast. The changes were mainly quantitative— 

use of two 14^2-inch cables on each side of the trunk with other elements proportionately heavy—but the design also specified built-up wrought-iron plate girders 

for the floor beams and wire-rope suspenders, both significant departures from the 

Delaware & Hudson aqueducts. (Courtesy Rensselaer Polytechnic Institute.) 

IV 

Proposed Railway Suspension Bridge 

This proposed suspension bridge was designed to carry the New York and 

Erie Railroad over the Lackawaxen River near the aqueduct site. Designed by 

Roebling while building the two aqueducts at Lackawaxen, it had many characteristics in common, particularly in the cable and anchorage systems. The deep, latticetruss-stiffened deck closely forecast that used in his Niagara railroad bridge begun 

four years later. The estimated cost for the bridge, with two spans of 195 feet each, 

was $11,040 for a single-track structure and $22,080 for a double. (Suspension 

Bridges Dec 1847 John A. Roebling, page 27.) (Courtesy Rensselaer Polytechnic 

Institute.) 

V 

Neversink Aqueduct 

Comparison of Roebling's Proposals for a 1- and a 2-span Structure * 

1 span 

7 span 2 span as built * * 

Clear span length (feet) 170 2 @90 160 

Cable diameter (inches) 9V2 6ZA 9l/2 

Cable length (feet) 261*** 266*** 203 

Cable weight, both, with wrapping 

(tons) 46.5 23 36 

Cable cost @ 10 cents per pound $9,200 $4,600 $7,490 

Anchor chain weight, total (tons) 13 4.5 22 

Total cost $24,900 $18,000 24,900 

*Suspension Aquaducts . . Febr. 1847. Data, about November 1847. 

**Never Sink Aquaduct . . . Oct. 1848. 

***The early plans proposed running the cables on the west shore through chases in solid 

rock directly to the anchor plates, as had been proposed for the High Falls Aqueduct, without 

intervening anchor chains. Distance, saddle to plate, 62 feet. 
NUMBER 10 43 

VI 

The Delaware Aqueduct Saddles 

(See Figure 47) 

Not all of the modifications to the Pittsburgh Aqueduct design made at Lackawaxen were for the better. In Wire Cables & Machinery . . August 1848, Roebling 

observes that the saddle pattern employed in the first two Delaware & Hudson 

aqueducts is unsatisfactory in having the seat for the cables too wide. At Pittsburgh, 

the space was just about as wide as the cable diameter so that the cable's circular 

section was preserved as it passed through the saddles. At Lackawaxen, he used a 

width of 11 inches causing the 8/2-inch cables to flatten considerably at that point, 

destroying the roundness of the strands and cables near the saddles and causing 

unequal tension in the individual wires (see also Figure 22). Despite these misgivings, 

the saddles of the two later aqueducts apparently were cast from the same patterns 

for the same widening and flattening is evident at High Falls (Figures 35 and 36). 

BibliographyDelaware & Hudson Canal Aqueducts 

BOOTH, MALCOM A. "Roebling's Sixth Bridge, 'Neversink'," The Journal of the Rutgers University 

Library, volume 30, number 1 (December 1966), 

pages 12-20. 

BOYNTON, H. C. "Bridge Wire Tested After 75 Years," 

The Iron Age (9 February 1928), volume 121, 

page 400. 

A Century of Progress—History of the Delaware & 

Hudson Company 1823-1923. Albany (J. B. Lyon 

Company, printers), 1925. Pages 108, 138-41, 195. 

The Delaware and Hudson Canal—A Brief Chronology 1763-1915. The Canal Museum: Syracuse, New 

York, 1966. [Three mimeographed pages.] 

Delaware & Hudson Canal Company. Annual Reports 

for various years, New York. 

JAKKULA, A. A. A History of Suspension Bridges in 

Bibliographical Form. Agricultural and Mechanical 

College of Texas, College Station, 1941, pages 127-8 

(Pittsburgh Aqueduct); 133-4 (Delaware); 138 

(Rondout); 140 (Lackawaxen and Neversink). 

[General dimensions and brief descriptions; bibliographies.] 

LEROY, EDWIN D. The Delaware & Hudson Canal— 

A History. Honesdale: The Wayne County (Pennsylvania) Historical Society, 1950. Pages 48-53. 

List of References on the Delaware & Hudson, 1923. 

[Mimeographed list compiled by Bureau of Railway 

Economics, dealing mostly with the railroad but 

some canal references.] 

"Mr. John A. Roebling," Journal of the Franklin Institute (6 November 1867), volume 54, page 411. 

[Describes briefly all four Delaware and Hudson 

Canal aqueducts as well as Roebling's six other 

bridges, including the nascent Brooklyn Bridge.] 

SCHUYLER, P. K. "Lackawaxen Suspension Bridge Rebuilt for Present-Day Use," Engineering and Contracting (November 1930), volume 69, page 421 

[Describes plans of Federal Bridge Company, which 

recently purchased bridge, to rebuild it.] 

SHAUGHNESSY, JIM, Delaware & Hudson—The History of an Important Railroad Whose Antecedent 

was a Canal Network to Transport Coal. Berkeley, 

California: Howell-North Books, 1968. Pages 6-13. 

[General description of the four aqueducts and the 

canal in general.] 
44 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 

"Suspension Aqueduct on the Delaware & Hudson 

Canal," American Railroad Journal, volume 22 (13 

January 1849). [Describes canal enlargement and 

gives statistics and rationale of structure.] 

STEINMAN, DAVID B. The Builders of the Bridge— 

the Story of John Roebling and His Son. New York: 

Harcourt, Brace and Company, 1945; revised edition, 1950, pages 101-105. 

United States Geological Survey quadrangle maps, 

7.5 minute series, showing Delaware & Hudson 

suspension aqueduct sites: Delaware and Lackawaxen, Shohola, Pa.-N.Y., 1965; High Falls, Mohonk Lake, N.Y., 1964; and Neversink (Cuddebackvitte), Otisville,N. Y., 1942. 

WAKEFIELD, MANVILLE B. Coal Boats to Tidewater— 

the Story of the Delaware & Hudson Canal. Printed 

by Steingart Associates, South Fallsburg, New York, 

1965. Pages 79-92. 

WHITFORD, NOBLE E. History of the Canal System of 

the State of New York. Albany, 1906. 2 volumes. 

[Supplement to the Annual Report of the State Engineer and Surveyor of the State of New York for 

1905]. 

"Wire Suspension Bridge," American Railroad Journal (7 July 1849), volume 22, page 421. [Physical 

description and dimensions.] 

American Railroad Journal, volume 18 (9 October 

1845), pages 648-649. 

Roebling's Allegheny Aqueduct and 

Monongahela River Bridge 

American Railroad Journal & Mechanics Magazine, 

volume 17 (1844). 

JAKKULA, A. A. A History of Suspension Bridges in 

Bibliographical Form. Agricultural & Mechanical 

College of Texas, College Station, 1941, pages 127-

130. [General dimensions and brief descriptions; 

bibliographies.] 

MAHAN, DANIEL H. An Elementary Course of Civil 

Engineering, New York, 1867, pages 272-76. [There 

are earlier and later editions as well.] 

"Mr. John A. Roebling," Journal of the Franklin Institute (6 November 1867) volume 54, page 411. 

[Describes briefly all four Delaware & Hudson Canal 

aqueducts as well as Roebling's six other bridges, 

including the nascent Brooklyn Bridge.] 

STEINMAN, DAVID B., The Builders of the Bridge—the 

Story of John Roebling and His Son. New York: 

Harcourt, Brace And Company, 1945; revised edition, 1950, pages 78-100. 

"Suspension Aqueduct on the Delaware & Hudson 

Canal," American Railroad Journal (13 January 

1849), volume 22, pages 21-22. 

WHITE, JOSEPH, and VON BERNEWITZ, M. W. The 

Bridges of Pittsburgh. Pittsburgh, 1928, pages 97-98. 

UNPUBLISHED SOURCES 

Two bodies of Roebling manuscript papers exist: 

The Roebling Collections in the Library of Rensselaer 

Polytechnic Institute, Troy, New York, and in the 

Special Collections of the Library of Rutgers University, New Brunswick, New Jersey. The former is 

a collection of vast scope and immense value, covering 

all of John A. and much of Washington A. Roebling's 

professional careers. There are many notebooks, letters, 

and reports, but the collection's crowning glory is a 

large number of drawings and sketches—design, presentation, study, and working. The entire collection 

was recently classified and cataloged by the author 

with a grant from the American Society of Civil Engineers. A published version is anticipated. The Rutgers 

Collection, while smaller, contains some material of 

great technical interest as well as personal items in the 

form of letters, diaries, and other documents. There is 

little graphic material. The collection is readily accessible and well cataloged. Oddly, the technical material 

in both collections overlaps to a considerable extent, 

the result apparently of haphazard handling and storage while the material was passing through various 

family hands. 

The first nine references below are all manuscript 

notebooks. The first four are from the Rensselaer Polytechnic Institute Collection; the next five from the 

Rutgers. Various other Rensselaer Polytechnic Institute letters, notes and drawings are cited individually, 

for which the Library catalog number is given. 

Rensselaer Polytechnic Institute Collection 

Cash Book—Delaware & Hudson Aquaducts [sic, 

Roebling consistently spells the word this way] July 
NUMBER 10 45 

1847 to June 1850 [first entry, 24 July 1847 for 

labor and freight to Lackawaxen site]. Roebling SciTech 300. 

Diary for 1847 [entries only to February, but covering 

R. F. Lord's Pittsburgh visit]. Roebling Sci-Tech 

283. 

Notes on Suspension Bridges (no date, about 1844-

1855) [Contains a great amount of data on his own 

and other suspension bridges, from observations, 

calculations, and publications. Much early design 

work for the Niagara Bridge, and both design and 

as-built data on the canal aqueducts.] Roebling SciTech 326. 

Notes on Suspension Bridges 1860 [Similar to 326 

above.] Roebling Sci-Tech 271. 

Rutgers University Collection 

Ledger John A. Roebling [Pittsburgh] Aquaduct, Monongahela Bridge. [Also covers early work 

on the Delaware and Lackawaxen aqueducts, particularly the contract work done in Pittsburgh on 

the anchorage iron in mid-1847.] 

Never Sink Aquaduct High Falls Aquaduct 

Oct. 1848 John A. Roebling. [Much additional 

design data and calculations.] 

Suspension Aquaducts Delaware and Hudson Canal John A. Roebling Febr. 1847 Delaware A. Lackawaxen Never Sink High 

Falls. [Contains the basic design data for all four 

structures, including cost estimates for the Neversink and High Falls spans.] 

Suspension Bridges Dec. 1847 John A. Roebling. [Principally design studies for bridge projects, 

e.g., over Genessee River, water-main aqueduct 

over East River, railroad bridge over Lackawaxen 

and Delaware & Hudson Canal (see Appendix IV) ; 

but also one page of post-mortem observations, 

with sketches, on Delaware Aqueduct cable 

making.] 

Wire Cables & Machinery August 1848 Important General Remarks Construction of 

Delaware A: Cables Niagara Bridge. [Nine 

pages of extremely detailed post-mortem notes, remarks, and comments on the cable making procedure at Lackawaxen, compared frequently with 

that at Pittsburgh.] 

Others 

Letter to L. N. Edwards from L. A. Porter, Bridge 

Engineer, Pennsylvania Department of Highways, 

26 September 1950, giving certain data on the 

bridge from the memory of a "Mr. Black." [Division 

of Mechanical and Civil Engineering, Smithsonian 

Institution.] 

ROEBLING, WASHINGTON AUGUSTUS. Design for a 

Suspension Aquaduct. Senior thesis (manuscript), 

Rensselaer Polytechnic Institute. Troy, New York, 

1857. [Original, Rensselaer Polytechnic Institute Library; microfilm and Xerox reproduction, National 

Museum of History and Technology Library, 

Smithsonian Institution.] 

&U.S. GOVERNMENT PRINTING OFFICE: 1971 0—406-927 

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

Washington, D.C 20402 - Price 65 cents