lowth~p truss bridge haer no. nj-19 on west main street

Lowth~p Truss Bridge On West Main Street, over the south

HAER No. NJ-19

branch of the Raritan River Clinton Hunterdon County New Jersey

PHOTOGRAPHS

WRITTEN HISTORICAL AND DESCRIPTIVE DATA

REDUCED COPIES OF MEASURED DRAWINGS

Historic American Engineering Record National Park Service

U.S. Department of the Interior P. O. Box 37127

Washington, D. C. 20013-7127

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Location:

Designer:

Fabricator:

Present Owner:

Significance:

HISTORIC AMERICAN ENGINEERING RECORD

Lowth8£P Truss Bridge

HAER No. NJ-19

On West Main Street, over the south branch of the Raritan River

Clinton, Hunterdon County, New Jersey

Francis C. Lowth~p

HAE NJv

William and Charles Cowin of Lambertville, New Jersey

Hunterdon County Department of Highways

The Lowth~p Truss Bridge represents an early type of iron truss that dominated bridge construction from the 1850s to the 1870s. Fabricated in 1870 by William and Charles Cowin of Lambertville, New Jersey, the bridge follows the Pratt configuration in the arrangement of its trussing members. It is of composite construction, with all compression members made of cast-iron and all tension members made of wrought-iron. In the Pratt truss, the vertical posts and horizontal upper chord are in compression and are made of cast-iron; the diagonals and bottom chord are in tension and are made of wrought-iron. Cast-iron members and lower chord connections are based on truss bridge patents received by Francis C. Lowthr~p of Trenton, New Jersey, during the 1860s and 1870s:

After 1870, engineers and fabricators favored bridges made exclusively of wrought-iron, as this material performed equally well whether subjected to tensile or compressive stresses. After 1890, wrought-iron was

r' supplanted by the stronger material steel. Lowthrpp \J

Truss Bridge, one of few known surviving examples of this type, is representative of the short-lived era (20 years) of composite cast and wrought-iron bridge construction. The Lowth(o'p Truss Bridge has been in service for over 100 years with only minor modifications, thus attesting to the soundness of its design, quality of craftsmanship and care of maintenance. It remains a distinctive feature of the town of Clinton, New Jersey. The following article was taken from the November 11, 1920, Engineering News-Record and contains much information on the history of F. C. Lowthrfp. Please note that two

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Project Information:

Transmitted by:

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Lowthtlop Truss Bridge HAER No. NJ-19 (Page 2)

Lowth~p trusses in Clinton, New Jersey, are discussed, one dating to 1859 and the other to 1870. Only the 1870 structure survives.

This recording project is part of the Historic American Engineering Record (HAER), a long-range program to document historically significant industrial and engineering sites in the United States. The HAER program is administered by the National Park Service, U.S. Department of the Interior.

Fieldwork on the bridge was completed during the summer of 1975 by the National Park Service, under the general direction of Douglas L. Griffin, Chief of HAER. Measured drawings, historical reports and photographs were prepared under the direction of Eric DeLony, Principal Architect, HAER. The 1975 measuring team consisted of Robert M. Vogel, Curator, Division of Mechanical and Civil Engineering, Museum of History & Technology, Smithsonian Institution; Arnold David Jones, HAER Architect; student architect R. Belmont Freeman (University of Pennsylvania) and volunteer Robert K. Holton, Essex Falls, New Jersey. Student architect Carolyn Givens (University of Kansas) completed measured drawings of the bridge during the summer of 1985. Formal photography was done by Jack E. Boucher and historical research was conducted by Donald C. Jackson, HAER Historian/Engineer.

Jean P. Yearby, HAER, 1987

Lowt~p Truss Bridge HAER NZ-19 (page 3)

_x_m_·~_m_be_r _1_1._19_2_o _____ E N G I N E E RI N G NEWS - RE CO R D 927

In response to a letter of inquiry regarding Mr. Lowthorp and his bridges addressed to his son Francis C. Lowthorp, Counsellor at Law, Trenton, N. J., the latter has given many interesting details. From his letter the following extracts are taken:

.Hy father, born 1810 in New York City, died June 1, 1890. He was a delicate child and was placed under the care of bis uncle, the late Dr. John Lilly, of Lambertville, W:ho succeeded iD. ma~ing a rugged man of him, putting hun into an outdoor hfe as a surveyor and engineer. He worked under Ashbel Welch on railroad and canal construction for a time. He went into the service of the Lehigh Coal & Navigation Co. and designed and superintended construction of BDme locks in its canal with a great lift. Afterwards be became bridge engineer for the Leh'gh Valley R.R. Co. Among other bridges he designed the first railroad. bridge across the Delaware at Easton, connecting the Lehigh Valley R.R. with the New York Central and the

Distribution of Snake River Wate1· During Gxea!est Drought

Continuous Flow Supercedes Intermittent Flashes -One Man Handles Storage and Natural

Flow Like Train Dispatcher

THE Snake River in Idaho is one of the State's greatest resources since it supplies water to a large per

centage of the total irrigated area. Policing the stream and distributing the water to the respective users in accordance with their rights is one of the most important rluties of the state. From Jackson Lake storage reservoir on the headwaters in Wyoming to the Milner dam, by which the two Twin Falls irrigation companies divert the last of the stored water, the distance is 300 miles. Intervening are more than 50 headgates, which

Belvidere & De!aware R.R., a atructure carrying tracks on two 18 , , I ~~ I : 1 levels. In 1857, acting as engi- I J, /' . , (' I'\ I I I I neer for Cartwright & Co., the ., 16 -,., 11 'n>J..-' -+-+-+-'- ~...+_,__,_-+-+-f-+-+-1 contractors for the Catasauqua ] J '' \ 1 ' : \ :.., ~-/<ii: 1905 Record obfQ/ned 'Qf-fno I & Foglesville R.R., he completed 5114 I I \ ·'J: \! N l;ton Go_qing Station near the Jordan Creek bridge, not far 6 : I i ~ u !SOS ai~r.n,. ~'t'/1,k~dal h ~ No sfo~ from Allentown, Pa. This wao i= \".. I l l. ' 1 I very adveraely criticised by some lr!. IZ i I I f-1, , I I / other engineers, and the predic- .;o; 10 " i f ' ,,;. I\ ,....... -ii: tion was made that it would fall Ii; H-+-+,+ r.'/9.-:-Vt9-++l-k',~.~ .-.H"li;l;..,t'-"',N;....'l.-rJ"'if1/lk--~+i~f"l-+-!-H""<l-++-+-IH-++++-1 with the first train to attempt .._ ._, ,~ I ~, ,v ,. Its pa111age. It turned out to 11::: 8 · \ I be one of the longeat-lived s ,J 'ii \Vt, I i I" :r,~-~~ ,- t \1'1Al ~ {"f brldgea be ever built; I think It 6 ~ 79/5 • ' ' • ' ·-,......., ,NATllRAJ. Fl.OW 1915-lltood for about ftfty years, de- .5 l\~J'1'-~· iNATIIRAl FJ.Ow',iJg 'r:,.. ~f.)...:-,,.. ,kl 1/\ api;e the constantly increasing ~,+ _ ~ _ !90S ' : 1 1 < ""- ~-:;,,. · ·, ~I 1'. i A I/ weight of rolling stock. cs - 1, /' / _

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Some years after the com- 1j , pletion of that bridge my father i:S Z j

1.

atarted into ·the engineering and contracting busine11 on his own o ... ~ ........... ~,:--'-'~--'~;-'--..,_..._.._.._.-;-.'; .......... _._ ...... t,:,:~ .......... -l:-~:-=i:'cc-L..J ru,omibilit;v. · Be ueed com- April May June Joly August :,eprember prea1lve members of caat iron, FIG. I-TOTAL A!'W l'.ATURAL FLOW OF SNAKE RIVER AT HIESE DURING u you know, and held to that THREE YEARS OF DROl.'GHT plan for many :,ears despite the -retitlon of others who used wrought-iron (and afterwa1'da stael) compreuive member,.

According to the l!8IDe authority, M:r. Lowthorp designed more than a score of bridges for the Newark & New York R.R. when thl1 wu built, and most of the bridges on the New York & Long Branch R.R. Thae latter included the Raritan Bay crouing, containing a awing 1pan that wu probably the longest ever built up to that time. He also built the original Newark Ba:, draw of the Central R.R. of New Jersey, besides other bridires on that road, and aeveral bridges for the New York, New Haven & Hartford R.R.

:Mr. Lowthorp took out patenta on hill designs of mnr brili8'8 centers and turntablell ; the latter in particular came into wide use, aome twelve being furnished to the Union Paciflc alone.

While the Raritan Bay draw wu replaced after very lllhort ue, lta removal and replacenmnt by another brilf8'e wu not chargeable to any defect in the design or iuly atructural objection to the bridge, but resulted from competitive railroad policy. Immediately after its eniction, llti,a tion developed, in the interests of the fennaylvania R.R~ which wu enarased in a campaign to Obtain an Interest in or eontrol over the Long Branch road to MCUre accas to the aeaahore resorts. The claim WU ~, that the bay crouing constituted an obstruc~ ~. 11&-riptfon. After the euccas of the campail'D, pw ....... ... nplaced hr a - structure.

by court decrees have priority rights of various dates. To apportion the. stored water and natural flow properly to the rightful ~ers when there is not enough to 1'0 around and late dec,ees must be cut off in successive order ia a difficult task. It requires an intimate knowledge of the hydrorraphy of the river, backed up by daily readings at the numerous gaging stations, and necessitates frequent changes of the canal headgates and storage reservoir outlet gates. Like a train dispatcher, the officer in charge of the distribution turns loose in a continuous ftow a definite quantity each day and must order t.he proper number of gates opened to care for it as well as the natural flow, plus or minus the amounts gained or lost in transit. Unlike the train dil!l)atcher, his container as well as earl(() must all be delivered at the end of the run.

Only within the last two years has one man been placed in complete control of the whole river but the results have been so satisfactory it ia not likely multiple control will again be revived. By a co-operative arrangement effected with the U. S. Geological Survey, it became possible to centralize under the control of one man both the hydrometric or stream measurement work and the distribution. Thia consolidation of State and Federal functions is a departure from the old method and has a distinct advantage in that there is no lost motion in obtaining the fullest and most complete information concernins all phaael of the river work. Another

Lowth{:lbP Truss Bridge HAER NJ-1 o.

(page 4)

N nvemoor 11. 1920 ENGINEERING NEWS-RECORD

Sixty-Year-Old Iron Bridge in a New Jersey Village Oldest of Several Lowthorp Truss Highway Crossings of Raritan at Clinton and High Bridge Carries Reg

ular Road Traffic-Floor Recently Strengthened-F. C. Lowthorp a Pioneer Iron Bridge Builder

BY R. FLEMING American Brtdgt> f'o., N .. .,. :fork <~t,·

IN THE village of Clinton, N. J., are two iron bridges built in 1859 and 1870, respectively, that interest the

engineer not only by their age but also by their type. The older of the two, though it has seen full sixty years of service, is still in excellent condition, with no discoverable change of importance except a recent Ptrengthening of the floor system. These structures represent an early type of iron bridge, now Jong extinct but at one time extensively used; little mention of the type is found in the writings of our standard authorities on bridges, though Francis C. Lowthorp, its originator. was a prominent bridge builder of his day. The type

the following, however, relate to the older of the two bridges at Clinton.

As shown by the drawing Fig. 1, made from measurement,, taken at the site by the writer, a Pratt web system is used in the bridge (the Pratt patent was issued in 1844). The compression members (top chord and posts) are of cast iron, while the tension members are of wrought iron. In sections of the top chord is cast the inscription, "Built for Hunterdon County by Wm. & Chas. Cowin. Lambertville, N. J., 1859. Lowthorp's Patent June 30 & Nov. 3, 1857." Because of the increasing traffic loads, the floorbeams were reinforced

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f'"(-·F-6" __ .,.. ____ --------16' ___________ '!!' ______ ...,

Seetion C. ·G (Eolargod)

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'lbp Chord

G'• :I ~H :,G' y ;:: floorbeam Attcachment

FIG.4a ) (From Lowth~rp's Patent

row1n

FIG.4b Cooperl:l'""' A S.c.E XX!

• _ .. .JGIL 1.'J'O Ii, LOWTHORP'BlGHWAY BRll)QE o;:;:~;ol~~5~R.,\NCH OF RARITAN RIVER AT CLINTON, N. J ..

t, ... .., -· ' .:•,:.:;·., :,.. ~.- .

~re fa an excellent representative of the comon ,trueture of cut and wrought iron which

Ill large a part in brlda'e construction about years ago, domlnatinr the field for a time.

/.Botb the bridges mentioned crou the South Branch ,1 1tie Raritan River; the 1859 bridge consiata of three ..,._ o1 561 ft. each, and the 1870 brldre of two 85-ft. ~ Two other Lowthorp bridges over the aame ~~ 4t High Bridre, some miles distant, bear the lllliil1167 and 1868, :Moat of the illustrations riven in

by kingpoet trussing in 1917 or '18, as shown in the crollS-MCtion, and steel joists were added. As the road was being macadamized, wood paving blocks were laid on the plank floor. So far as determinable, all the 1'911: of the bridge is old.

Fir, 2 shows a top-chord joint and Fig. 8 a bottom• chord joint. This 11&me bottom-chord joint la lhown in the photograph of an intermediate post, Fig. 6. Mr. Lowthorp's patent of June 80, 1857 was based on a bottom chord joint u ehown in F!Jr. 4a (renroduced

LowthtpP Truss Bridge HAER NJ-19 (page S )

926 ENGINEERING NEWS-RECORD Vol. i('lic,'9

from Patent Office Report, 1857), The claim of the patentee is, "The straining piece B, in combination 1ritb the rods G and H, when the latter are connected to the plate substantially in the manner set forth, and when the said plate is uranged to receive the vertical or verticals A and D, E of iron truss frame bridges."

The floor beams are 9-in. wrought iron J's with 4-in. flanges and Hn. webs, now reinforced by trussing. They are fastened at each end 1rith 4 bolts to the cast iron "straining piece." The beams bear the imprint, "Patented Dec. l, 1857." The main and counter diagonals have screw adjustment at the lower ends, and the bottom-chord rods are connected longitudinally with screw "s11'ivels" or sleeve nuts at each panel-point. All screw ends are enlarged. The diagonal bracing in the plane of the bottom chord consists of a pair of rods in each panel.

The workmanship of the bridge was excellent. This is evidenced by the fact that it has lasted 60 years and is still in good condition. The bridge presents a much better appearance today than the majority of pony trusse.• built at a later date. It Is( however, frequently overloaded. During the tw.p hours ·while measurements were being taken there passed over the bridge 85 automobiles, 2 auto-trucks and 2 teams, and later in the day a large moving van from a city 50 miles distant. The writer was told of an auto-truck that crossed a day or two before loaded with 12 tons of cement. Even allowing for exaggeration in this statement, it confirms the writer's opinion that auto-truck loading unless more effectively restricted than at present, will result in the failure of this and other old highway bridges.

As well as can be judged, the bridge .was probably designed to carry a moving load of 50 lb. i,l!r sq.ft. on the roadway. The floorbeam reinforcement lftld the wood paving blocks add 12 or 18 lb. per sq.ft. to the original dead load. Considering the total dead weight of the present bridge to be 900 lb. per Jin.ft. ( of which 525 lb. is carried by the walk truss, the reader can easily make his own calculations for permissible loading. The heavy moving loads of today were unknown 60 )·ears ago.

The 1870 bridtre, ''built by Wm. Cowin, Lambertville, N. J.," is of the same ~'J)e as the 1859 bridl!'e, The truss that was measured is 9 ft. deep center to center of chords and is divided into 8 panels of 1 O ft. n in. each. The diagonals in each panel are of two rods instead c,f one as in the older bridge, and pins are used in bottom as well as top chord. An occasional pair of main diagonal$ has the adjustment in one rod shon in Fig. 5, Just when this peculiar form of adjustment at irregular intervals throu,hout the four trusaes was made is not clear.

It may be fttting to give some general factF- regarding the Lowthorpe bridge, of which ~'J)e a considerable number were built in the '60s and '70s. They were designed in accordance v.-ith correct engineering principles. The fl'J)e of truss, known as the Lowthorp Trapezoidal Truss, was of either Pratt or Whipple web arrangement, and had counters in all except the end I sometimes the end two I panela. The compression members were of east iron and the tension members of wrought iron.

:\Jr. Lo"'thorp wa• · 11 ftrm believer in the merii. of ,as! iron. A paper. ··on the Use of Cast Iron for Corr,. r1e,sh·r lllemhfors o1 Iron Bridges." read by him at th" ~rrnnC"' ~r.T'lm.! rnn,·en!ion "f the Ameriran f;oritt,t~·

of Civil Engineers, held lune, 1870 .(Tnl~ A. S. C. E. Vol. 1, page 228) closes with an intereat:lq expression of opinion: "The practical experience -most engineers and builders will justify me iD the -rtion that there is much more to be feared from defects in wrought iron used for tensile than in cast il'OII ned for compressive purposes."

A commission appointed by the city of Philadelphia (Ashbel Welch, 1. Edgar Thompson and lobn C. Cresson) in 1858 offered a premium for the best des~ of an iron bridge truss. In awardins the fint premiam to Mr. Lowthorp it said of his deaign, "It is well porportioned in all ita parts, which are so disposed as to afford a maximum of strength with the amallest amount of material, havins such arrangement for aiijuaiment as to give each and every part its proper fwu:tion to

FIGS. & A.ND 7. INTl!lR.MEDlATE POST AND ABl'T.1,[11:NT PO~T

perform, without requiring great experience for its care."

In 1856-7 Mr. Lowthorp designed and built his first -railroad bridge. The bridge crossed the valley of Jordan Creek on the line of the Catasauqua & Foselsville R.R. near Allentown, Pa. It consisted of 11 spans with a total length of 1,120 ft .. supported on piers of cast and wrought iron varying in height from SO to 54 ft. anchored to mason11· foundations, making a total height in places of nearly 90 ft. The trusses, of the doubleintersection type, 12 panels each, were 16 ft. high and were spaced IO ft. apart center to center. At the time of ih completion this waF one of the longest if not the longest of iron bridge~ in the United States.

AD interestin1I feature in many of the Lowthorp bridge~ was the hip vertical, where for uniformity in appearance a cast-iron member similar to the posts was used. 1 nside of this member was placed a wroughtiron rod to take the tensile stress from the floor beam.

\\o'hile most of the Lowthorp bridges have been replaced as they were outgrown by the traffic loads, a 60-ft. deck span of three trusses, with 34-ft. roadway and two 7-ft. walks, still exists at the Jackson Ave. crossing over the tracks of the Central R.R. of New Jersl')" in Jersey Ci~·. A trolle~· traverses thl' bridge. but the trolley tracks, laid long after the bridge was bnilt. are trusged b::ims extending from abutment to ahutmen!

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ADDENDUM TO LOWTHORP TRUSS BRIDGE

HAER No. NJ-19 (Page 6)

HISTORIC AMERICAN ENGINEERING RECORD

WEST MAIN STREET BRIDGE (Lowthorp Truss Bridge)

HAER No. NJ-19

This report is an addendum to a 5 page report previously transmitted to the Library of Congress in 1987 .

Location:

Date of Construction:

Fabricator:

Present Owner:

Present Use:

Significance:

Historian:

.,

Crossing the south Branch of the Raritan River on West Main Street, Clinton, Hunterdon County, New Jersey.

UTM: 18/507390/4498120 Quad: High Bridge, New Jersey

1870

William Cowin Cowin Iron Works Lambertville, New Jersey

Office of the County Engineer Hunterdon County Administration Building, Main Street, Flemington, NJ 08822

Pedestrian and vehicular traffic with load limits.

The West Main Street Bridge is one of three existing Cowin-fabricated spans in New Jersey. It is also one of two Cowin bridges that used William Johnson's patented tension adjuster.

Robert w. Hadlow, August 1991

WEST MAIN STREET BRIDGE HAER No. NJ-19

(Page 7)

The West Main Street Bridge, spanning the South Branch of the Raritan River on Clinton's West Main Street, is a two-span composite cast- and wrought-iron pony-Pratt truss. It is one of the oldest all-metal bridges in the United States and is one of three existing spans that William Cowin fabricated at his iron works in Lambertville, New Jersey. In all of them, Cowin employed components that Trenton engineer Francis c. Lowthorp had patented in the 1850s and 1860s. The two other existing bridges are also located in Hunterdon County, north of Clinton, at New Hampton (1868) and at Glen Gardner (1870). A fourth bridge, located on the north edge of Clinton, over the South Branch of the Raritan on Halstead Street, was built in 1859. It collapsed under the weight of an overloaded truck in the late 1920s.

Composite cast- and wrought-iron bridges form part of the progression in American bridge design from the 1850s to the early 1870s. Widely perceived as more durable that all-wood or composite wood and iron spans, composite iron bridges used cast iron for all members under compression and wrought iron for all members in tension. Cast iron, because of its brittleness, was unsuitable for situations involving bending and tension, while wrought iron, though equally suitable in compression or tension applications, was prohibitively expensive, driving fabricators. to use less expensive cast iron wherever possible. Nevertheless, the popularity of composite iron spans waned with the advent of less costly methods for producing wrought iron and steel after the Civil War. By the late 1870s composite cast- and wroughtiron bridge fabrication had nearly vanished, with the exclusive use of wrought iron in bridge fabrication. By the 1890s, steel had supplanted iron as the material of choice.

Previous Spans

Pioneers began operating mills along the banks of the South Branch of the Raritan River at the present-day site of Clinton in the 1763, when David McKinney built a linseed mill on the west bank of the river. By 1810, Ralph Hunt operated a woolen mill at the site. John B. Taylor and J. W. Bray, subsequent owners of the land and collection of buildings, continued the milling business in the 1830s. They also invested in local real estate, and were probably responsible for changing the name of the settlement from "Hunt's Mills" to "Clinton," in honor of New York Governor DeWitt Clinton. 1

Taylor and Bray sold the mill after suffering financial disaster in the panics of the mid-1830s, and new owners took advantage of the nearby limestone quarry and kilns to mill plaster. After many interim owners the mill became the property of Philip Gulick


(Page 8)

in 1873, who improved the collection of buildings, including enlarging the mill to house four stones with which he ground grain. 2

A "bird's eye view" panorama map of Clinton from 1886, by T. M. Fowler, includes an 1840 inset depicting a span on West Main Street over the South Raritan. This structure appears to be a triple-span king post wooden bridge, but no sources have been uncovered that reveal whether or not it was swept away in the freshet of 1862 that took out bridges all along the Raritan, Lehigh, and Delaware rivers. 3

Clinton and the surrounding region experienced another period of extremely heavy rains in early October 1869 that again carried off scores of bridges along the same rivers, including "the Covered Bridge" on Main Street. One might speculate that the king post span was replaced sometime between 1840 and 1869, or that it was covered in the interim. At least one townsperson, a Robert Rodenbaugh, lost his job after the freshet swept away the bridge: he had earned one dollar per month as its lamplighter. 4

To Erect an Iron Bridge

Hunterdon County's Board of Chosen Freeholders met often during the month of October 1869 to conduct "bridge viewings" to survey the damage done by the high water and make recommendations on the construction of replacement bridges. They met in Clinton on 9 October to view the site of the covered bridge over the south Raritan on West Main Street. The board agreed to erect an iron bridge to replace the former structure, although one member amended the resolution, calling for a two-span bridge rather than one. The Board also toured a nearby crossing over the Spruce Run, three miles north of Clinton, at Glen Gardener, and voted to appoint a committee to oversee construction of a new replacement bridge at that site.

No reason was given for the freeholder's interjection. Rail service did not reach the western part of Clinton until December 1875, when the Lehigh Valley Railroad opened a station on the west side of the Raritan. One might conjecture that the limestone quarry on the bluffs west of Clinton had, in the course of business, regularly carted stone across the old span, and the freeholder may have voiced concern for the live load capabilities of a single-span iron bridge. Moreover, Clinton's Main Street formed part of the heavily travelled Easton to New Brunswick turnpike, warranting a substantial, long-lasting structure. 5


(Page 9)

On 13 May 1870 the Clinton Democrat reported that a "handsome new Iron Bridge .•. is being drawn here by piece-meal ... and we hope it will soon be ready for use." William Cowin, proprietor of the Cowin Iron Works, of Lambertville, secured contracts for both the West Main Street and the Glen Gardner spans. He had already fabricated at least two other spans for the Freeholders, one in Clinton in 1859 (a 56 1 -6 11 -long pony-Pratt truss cast- and wrought-iron bridge on Halstead street at the village's north end), and another at nearby New Hampton, in 1868. Cowin, like Charles N. Beckel, a counterpart in Bethlehem, Pennsylvania, used components in his bridges that followed patents held by Trenton engineer Francis C. Lowthorp. 6 On Halstead Street, Cowin had employed a lower-chord casting and general truss arrangement that Lowthorp had covered in his patents of 23 June and 3 November 1857. 7

Description of the Bridge

The West Main Street Bridge is a counter-braced pony Pratt truss consisting of two eight-panel spans. Known as a "Lowthorp trapezoidal truss", it lacked lower chords in the end panels. 8

Lowthorp did not specifically patent this feature, although it was illustrated in his patent claim of 3 November 1857.

A Pratt truss is a simply-supported spanning structure in which the chords resist the structure's tendency to bend by developing internal compression forces at the top and tension forces at the bottom. The web resists overall shear by developing internal compression forces in vertical panel posts and tension forces in diagonal braces. Iron bridges from the 1850s through the early 1870s typically used less expensive cast iron, a brittle material weak in tension, for compression elements, and wrought iron, a strong ductile material, for tension elements. Designers proportioned structural members to resist forces efficiently while minimizing material and, consequently, weight and costs.

The 9' high cast- and wrought-iron superstructure spans nearly 85' from stone abutments at each embankment to a mid-river, concrete-encased, battered masonry pier. The plan is skewed approximately 10 1 to accommodate the central pier's alignment with the direction of waterflow. The roadway deck is 18' wide between trusses with 6' cantilevered sidewalks. The bridge used two kinds of end supports: a stationary support restraining lateral movement at the central pier, and roller supports permitting longitudinal extension and contraction at the embankments.

The truss is a continuous structure with an intermediate support that behaves as two separate spans sharing an end post. A


(Page 10)

continuous structure would arch over the center support, developing tension in the upper chord and compression in the lower chord. In the West Main Street Bridge, however, the lower chord, because of its slenderness, cannot resist significant compressive force, while the upper chord, because of its material and connection design, cannot resist significant tensile force. The tendency for the upper chord to pull apart and the lower chord to buckle create a kind of discontinuity. A simple analysis shows that the lower chord segments of the panels adjacent to the central pier could be eliminated while the bridge remains intact. In the actual bridge, the degree to which the structure behaves continuously or not could be affected by the amount of initial tensioning force applied to the lower chord and panel braces. Theoretically, compression force resisted by the lower chord could be counteracted by the available initial tensioning.

The upper chords of the bridge are hollow octagonal iron castings, a rigid material preventing the tendency of long, unbraced compression members to buckle or bend out under compressive force. The upper chord connections are cast-iron hollow boxes modified to provide socketed fittings for chord segments and a through-pin for the connection of panel brace rods.

The web posts are tapered cast-iron "I" sections with web openings divided by horizontal stiffener bars into five panels. The posts spread with increasing depth toward the base, accommodating the lower chord pin connection and stabilizing the truss laterally. Hip verticals were made from members identical to the web posts. This variation on the usual Pratt truss arrangement in which hip verticals act in tension as suspenders supporting the lower chord was a modification stemming from the incorporation of counterbraces into the end panels.

William Cowin braced each panel with wrought-iron rod pairs that increased in diameter toward the supports where overall shear forces in the truss (due to the bridge's self weight and symmetrical deck loads) were greatest. With the exception of the panel braces at the embankments, single rod counter-braces passed between each brace pair to stabilize the truss when loaded on one side only, an essential function for all light weight iron trusses carrying live loads that were large compared to the structure self weight. To prevent the braces from loosening when the counter-braces were in action, it was customary to give the braces, counter-braces and lower chords an initial tension. This initial tensioning developed internal forces in an unloaded bridge that combined with the forces caused by applied loads to stiffen the bridge.


(Page 11)

In the West Main Street Bridge, brace rods could be tightened at the lower chord connection pin with a tension adjuster patented by William Johnson, of Lambertville, New Jersey, on 29 November 1870. The adjuster incorporated planetary gears with locking devices at the pin. In his patent claim letter, Johnson explained how his invention allowed the bridge to be more easily assembled when lower chord and panel brace rods were fully extended. The initial tensioning of the lower chords and panel braces was accomplished by rotating the Johnson adjuster. Johnson's patent illustrations showed a web post very similar to those in the West Main Street bridge, suggesting that Johnson's patent, rather than Lowthorp's, was a primary design source.

Although this bridge has been classified as one of the New Jersey Lowthorp truss bridges, Cowin's fabrication differed significantly from Lowthorp's patents. 9 Instead of adopting Lowthorp's cast-iron lower-chord connection plates as he did in his 1859 bridge, also in Clinton, Cowin used simple wrought-iron pins. The lower chord, composed of two wrought-iron square bars, and panel bracing rods were fastened to the pin with forged eyes. The pin passed through holes in the flanges at the base of the web post that were enlarged and modified to provide anchorage for rod stirrups suspending the wrought-iron deck beam. This is similar to Lowthorp's patented invention of 3 November 1857 in that both designs had lower-chord pin connections. cowin's version, however, did not incorporate Lowthorp's web post connection details or continuous lower-chord plate and is more appropriately identified as a simple pin connection instead of a Lowthorp invention.

Confusion in identification of the sources for this Lowthorp truss bridge is indicative of the experimental design activity of this period. Designs frequently were, and still are, identified according to how they appeared rather than how they functioned; not only by lay observers but by fabricators and designers as well. Variations on inventions inspired further variations leading to unique designs not easily identified with a particular patent or designer.

Repair and Maintenance on the Bridge

Records of repair and maintenance for the West Main Street Bridge over the South Branch of the Raritan in Clinton are unavailable for the years up to 1943. A "bridge card" for the span shows a list of regular maintenance from then until 1977. The Hunterdon County Engineer's office covered the post-1977 years in periodic inspection reports prepared by outside consultants. 10


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The deck beams on the West Main street Bridge have been reinforced with queen post trussing. Records from 1943 to 1977 make no mention of this modification, but do indeed note that the bridge was "reconstructed" in 1938. These additions to the spans may date from then or possibly from two decades earlier, in the late 1910s, when the county added king-post trussing to the Halstead Street span at Clinton to make it capable of safely carrying heavier live loads. That span, though, collapsed in the late 1920s under the weight of an overloaded freight truck, and may have prompted county officials to rebuild the West Main Street Bridge on Clinton's West Main Street. 11

From 1943 until 1977, the bridge underwent routine maintenance. Crews replaced wooden planking on foot walks, repainted the masonry pier, and repainted the entire structure. They also replaced a number of cast vertical posts. Most likely these compression members cracked with age or were damaged by motor vehicle collisions. The wood road deck has been replaced with meshed metal, but the date of this modification is unknown. 12

Since the 1980s the bridge has received biennial inspections by the firm of A.G. Lichtenstein & Associates of Fair Lawn, New Jersey. A 15 December 1988 report of findings revealed that the structure had rusted floor beams, "cracks at the truss verticals, and additional spalling of the substructure components .... " The firm gave it a low live load rating and recommended complete replacement of the span at a cost of $1,896,000 for materials alone. 13

In May of 1989, Lichtenstein and Associates clipped a sample, or coupon, from a floor beam bottom flange on which it completed destructive analysis. The firm hoped to better understand the member's composition and therefore its durability. Microscopic and chemical tests determined that the sample had a "microstructure typical of wrought iron." In stress testing it developed a tensile strength of 48,800 pounds per square inch and yield strength of 32,800 psi.M

The bridge at present is restricted to passenger automobile and light truck traffic, moving only in an easterly direction. It is part of the historical setting, an extension of Clinton's late-19th-century Main Street business district.

Project Information

This recording project is part of the Historic American Engineering Record {HAER), National Park Service. It is a longrange program to document historically significant engineering and industrial works in the United States.


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The Cast- and Wrought-Iron Bridges Recording Project was cosponsored in 1991 by the Historic American Engineering Record and the West Virginia University Institute for the History of Technology and Industrial Archaeology. Fieldwork, measured drawings, historical reports, and photographs were prepared under the general direction of Dr. Robert J. Kapsch, Chief, HABS/HAER; Eric N. DeLony, Chief and Principal Architect, HAER; Emory L. Kemp, Director, Institute for the History of Technology and Industrial Archaeology; and Dean Herrin, HAER staff Historian.

The Recording Team consisted of Christine Ussler (Architecture Faculty, Lehigh University), Architect and Field Supervisor; Christine Theodoropoulos, P.E. (Architecture Faculty, California State Polytechnic University, Pomona); Wayne Chang (University of Notre Dame), Monika Korsos (Technical University of Budapest, Hungary, US/ICOMOS), Architectural Technicians; Robert w. Hadlow (Washington State University), William Chamberlin, P.E., Historians; and Joseph E. B. Elliott (Muhlenberg College), Photographer.

In the summer of 1975, HAER, under the direction of Douglas L. Griffin, sent a field team to Clinton to record the West Main Street Bridge.

APPENDIX 1. Francis C. Lowthorp15


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Francis C. Lowthorp was born on 8 February 1810 in New York City to Thomas and Mary Ann (Lilly) Lowthorp. Born in London, England, in 1782, Thomas emigrated to the United states in 1798 and soon settled in Albany, New York, where he met his future wife, the daughter of the Rev. Samuel Lilly. Moving to New York city, he worked for Elias Kane, one of the city's leading importers. In 1810 the Lowthorps moved to Geneva, New York, where Thomas entered the wholesale and retail general merchandise trade. He formed the firm Thomas Lowthorp & Company, with Kane and William Lilly as associates.

In 1813, Lowthorp was part of a consortium that applied for a charter for the Seneca Lock and Navigation Company to open a water route between Seneca and Cayuga Lakes. He was so well respected by his friends that the Order of Cincinnati bestowed upon him an honorary membership.

The third child in his family, Francis was in constant poor health as a youngster and his parents sent him to live with an uncle, Dr. John Lilly of Lambertville, New Jersey. There, he presumably recovered from his sickliness.

Lowthorp began his long career in the field of engineering as a young man working for Ashbel Welch on construction of the Delaware and Raritan Canal. He later became the principal assistant engineer on the building of the Upper Grand section of the Lehigh Coal and Navigation Company's canal. This extended though the Lehigh Valley from White Haven to Mauch Chunk, Pennsylvania. Lowthorp had direct supervision over construction of several locks on the system, including a 65 1 single-lift lock above Penn Haven.

In 1838, after completion of the Upper Grand section of the canal, Lowthorp and three partners erected an iron furnace at Mauch Chunk. There, they smelted anthracite iron. In this process, iron ore is refined with the hot blast that anthracite coal creates. Aware of English success with this method, the partners knew that no one in the U. s. had as yet perfected it. They became the first in this country to market the high quality product.

Lowthorp soon designed and oversaw the construction of bridges for the Beaver Meadow Railroad. Eventually, he received the "first award" for plans for an iron bridge carrying Chestnut Street across the Schuylkill River in Philadelphia. He then designed and built the Pennsylvania Railroad bridge over the Susquehanna in Harrisburg.


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From 1851 to 1854, Lowthorp was the bridge construction engineer for the LVRR. He designed the first railway bridge across the Delaware River at Easton, Pennsylvania. A two-tiered span, it connected the L.V.R.R. with the New York Central and Belvedere & Delaware railroads.

During 1856 and 1857, he worked for the firm of Cartwright and Company designing and superintending erection of the Jordan Creek bridge near Allentown, Pennsylvania, for the Catasauqua & Foglesville Railroad. This 1,120-foot span was 89 1 above the river and built solely of iron. Many engineers criticized Lowthorp's simple design and placed bets on when it would collapse under load. The bridge, though, outlasted its detractors and carried machinery far heavier than anyone had envisioned.

Lowthorp became a consulting engineer and designed many more spans. He was best known for those associated with the Newark & New York and the New York & Long Branch railroads. For the latter road his most notable contribution was a swing span across the Raritan Bay. In 1864 he built the original Newark Bay drawbridge for the Central Railroad of New Jersey. Only in 1926 was it replaced by a vertical-lift span designed by J. A. L. Waddell.

Lowthorp held many letters of patent related to the design of iron bridges. They included the following:

26 May 1857

30 June 1857 3 Nov 1857

13 Mar 1860

19 Feb 1867

#17,383

#17,684 #18,548 #27,457

#62,278

"Improved Hydro-dynamic Machine for Testing Strength of Materials"

"Iron Truss-Frame for Bridges" "Iron Truss-Frame for Bridges" "Plate for Securing Chords, Braces,

&c of Truss-Bridge, &c" "Improvement in Truss-Frame

Bridges"

Today, less than a handful of 1860s and 1870s cast- and wroughtiron bridges in eastern Pennsylvania and western New Jersey include elements for which Lowthorp held patents.

He was elected a member of the America Society of Civil Engineers in 1868 and became a fellow of that organization in 1870. He retired from the profession in 1876.

Lowthorp married Anna B. Chambers at Beaver Meadow, Pennsylvania in 1841. She was the daughter of a Clark Chambers. The Lowthorps had two children, Francis c., Jr., and Mary. Lowthorp married a second time, to Anna M. Bailey in 1868. His son Francis became a prominent Trenton attorney.


(Page 16)

Francis C. Lowthorp lived his retirement years in peace and died of natural causes on 1 June 1890 at home at 152 Greenwood Avenue in Trenton. According to his will and estate inventory he left his second wife and children nearly $30,000 in assets, a large sum in the late 19th century.

APPENDIX 2. William H. Cowin16


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William H. Cowin was a builder of iron bridges who lived most of his life in and around Lambertville, New Jersey, along the Delaware River. Born in 1825 in England to William H. and Sarah Cowin, the family emigrated to the United States between 1830 and 1840, but did not settle in western New Jersey until sometime after 1840. In 1850, William, Sr. listed himself as a molder in a Lambertville foundry, By 1849, William, Sr. had established an iron works (with a partner named Laver), and the following year Census records list him as a molder in a Lambertville foundry. Records of the Mount Hope Cemetery of Lambertville list William, Sr.•s death in June, 1859.

William, Jr. was connected with the iron and bridge industries from at least 1850, when he identified himself as a pattern maker to the Census enumerator. Ten years later, he owned a foundry and machine shop in Lambertville. Bridge insignia suggest that William, Jr., may have worked in the bridge building business with a brother, Charles: on the upper chord castings on the bridge erected on Halstead Street in Clinton, New Jersey, appeared the inscription "Built for Hunterdon County by Wm. & Chas. Cowin, Lambertville, N.J., 1859. 11

Cowin built at least three other cast- and wrought-iron bridges in Hunterdon County, and may have designed or constructed others. All four spans that he erected for Hunterdon County, one in 1959, one in 1868, and two in 1870, included castings and other features that employed details to which Francis c. Lowthorp of Trenton held patents.

The Cowin Iron Works, later named the Lambertville Iron Works, made Cowin a wealthy man, permitting him to build a large Tuscan Revival home in Lambertville in 1867. He also married well, wedding the daughter of Ashbel Welch, at one time president of the Belvedere & Delaware Railroad.

During the 1860s, Cowin diversified his interests. In 1866 he organized and presided over the Amwell Mills Company in Lambertville, briefly manufacturing cotton thread before the economic panics of the 1870s forced the firm's failure. Cowin also helped create the Lambertville Paper Manufacturing Company, producing manilla and flour-sack paper for the Philadelphia and New York markets. He died in 1874 or 1875. 17

After Cowin's death, Ashbel Welch, Jr. took over operation of the Lambertville Iron Works, producing patented axles, safety boilers, and steam engines. The firm disappeared in the 1890s. 18

APPENDIX 3.

Bridge Dimensions


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Truss type • . . . . . . . . . . . . . . . Pratt pony truss Number of spans . . . . . . . . . . . . . . . . . . . . . . 2 Total number of panels on north truss line ......... 16 Panel width, center to center of web posts (average) 10 1 - 7 1/2" Bridge length, Ln0 to Ln16 ••••••••••••• 170'- 11 1/2 11

Bridge length, Ls0 to Ls15 • • • • • • • • • • • • • 160'- 3" Maximum span, Ls0 to Ls8e . . • . . . . . . . 8 5 ' - 5 11

Minimum span, Ls8w to Ls15 • • • • • • • • • 7 4 ' - 4 1/2 11

Distance between upper and lower chords, center to center .... . . . . . . . . . . . . . . . . . . . Truss spacing .•...............

. . 8 1 - 10 3/4 11

17'- 10 1/2 11

Deck span, between truss centerlines, along skew Distance between CL of truss to CL of sidewalk rail. Sidewalk span, CL of truss to rail CL, along skew ..

18'- 0 11

6 1 - 1 5/8 11

6 1 - 6 11

Data Limitations


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Various sources were consulted in preparing this report. They include local, county and state government records, historical society archives, and library holdings. Town of Clinton records were limited to Council Minutes. Most County Records, located in the Hall of Records in Flemington, were indexed by name or subject, but the only collection relevant to this report was the Minutes of the Board of Chosen Freeholders.

In New Jersey, bridges on village, township, or county roads are under the jurisdiction of the county engineer. Because of this, construction and maintenance records for this bridge are found at the Office of the County Engineer, in Flemington. They offer little information until the early 1980s.

Records of the New Jersey State Archives and Library yielded genealogical records of the Lowthorp family and the will and estate inventory of Francis c. Lowthorp. The Hunterdon County Library, near Flemington has a ''Jerseyana" collection of books and pamphlets on the history of New Jersey. The Hagley Museum, Wilmington, Delaware has no records on William Cowin or Francis C. Lowthorp, nor does the New Jersey State Historical Society.

ENDNOTES


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1. "Hunt's Mill," n. p. , n. d. , TMs, held by Clinton Historical Museum, Gulick's Mill, Clinton, NJ, [1], passim. This footnoted manuscript history includes land title searches and establishes the provenance of the mill sites on both sides of the South Branch of the Raritan River, in Clinton.

2. Ibid.

3. "Historical Facts on Lehigh River Floods Recalled in Lecture," Globe-Times (Bethlehem, Pennsylvania), [May 1931), in Scrapbook Collection, Bethlehem Room, Bethlehem Public Library.

4. "A Sweeping Flood. Widespread Devastation. The Freshet in Clinton," Democrat {Clinton, New Jersey), 8 October 1869, 2; "Minutes of the Town Council," 2 April 1869, in Town Records, Clinton, New Jersey, 1865-1881.

5. The Board of Chosen Freeholders is similar in composition to the Board of County Commissioners form of government. See Minutes for 9 October 1869, Minute Book for 1864-1886, Board of Chosen Freeholders of Hunterdon county, located at Hall of Records, Flemington, New Jersey.

6.See HAER No. PA-206, Walnut Street Bridge, Hellertown, Northampton County, Pennsylvania

7. R. Fleming, "Sixty-Year-Old Iron Bridge in a New Jersey Village," Engineering News-Record, 11 November 1920, 925-27.

8.R. Fleming, "Sixty-Year-Old Iron Bridge in a New Jersey Village," Engineering News-Record, 11 November 1920, 925-27.

9.See the HAER report on Walnut Street Bridge, HAER No. PA-206, for a discussion of Lowthorp patents dated 30 June 1857 and 13 March 1860.

10. See records located at Office the Engineer, Hunterdon County Government Center, Flemington, New Jersey.


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11. See "Bridge Card," Bridge No. Nl, Office of the County Engineer, Hunterdon County, Flemington, NJ; Fleming, 925.

12. "Bridge Card," Bridge No. Nl, Office of the County Engineer, Hunterdon County, Flemington, NJ.

13. A. B. Lichtenstein and Associates, "NJDOT--Bureau of Structural Evaluation, Re-Evaluation Bridge Survey Report, Cycle No. 2, 11 Bridge No. lOXXONl, Office of the County Engineer, Hunterdon County, pp. 2-1 and 2-2.

14. Ibid., p. 2-7.

15. For sources on the life and activities of Francis c. Lowthorp consult the following: R. Fleming, "Sixty-Year-Old Iron Bridge in a New Jersey Village: Oldest of Several Lowthorp Truss Highway Crossings of the Raritan ... ", Engineering News-Record 11 November 1920, 925-927; "Memoirs of Deceased Members--Francis C. Lowthorp, F.Am.Soc.C.E.," Proceedings of the American Society of Civil Engineers, 32(1894)196-98; Death notices and court documents are found in: "Death of Francis C. Lowthorp," Daily State Gazette (Trenton, New Jersey), 2 June 1890; "Death of Francis C. Lowthorp," Trenton Times, 2 June 1890; "Last Will and Testament of Francis C. Lowthorp," Proved 23 July 1890, Book L of Wills, Folio 200, Surrogate's Office, Mercer County, New Jersey, also held by New Jersey State Archives, Trenton, in docket 4665-K; "Inventory of the Estate of Francis c. Lowthorp," Proved 10 November 1891, Book L of Wills, Folio 496, Surrogate's Office, Mercer County, New Jersey, also held by New Jersey State Archives, Trenton, in docket 4665-K; Family lineage is found in: Edwin Robert Walker, et al., A History of Trenton, 1679-1929 (Princeton: Princeton University Press, 1929), 576, 621."Unconnected Immigrants," in E. B. Huntington, A Genealogical Memoir of the Lo-Lathrop Family in this Country, Embracing the Descendants, as far as known. of The Rev. John Lothropp. of Scituate and Barnstable. Mass .• and Mark Lothrop, of Salem and Bridgewater, Mass .• and the First Generation of Descendants of other names (Ridgefield, CT: Mrs. Julia M. Huntington, 1884; reprint edition, Portland, OR: E. H. Lathrop, 1971), 409-10 (pages from reprint edition).

16. The following information is based on research by Terry Karschner, Curator for the Historic Sites Section of the New Jersey Department of Environmental Protection, in manuscript records of the U.S. Census; James P. Snell, History of Hunterdon


(Page 22)

and Somerset Counties, New Jersey (1881). On Cowin's early bridge building, consult: R. Fleming, "Sixty-Year-Old Iron Bridge in a New Jersey Village: Oldest of Lowthorp Truss Highway Crossings of the Raritan ••• ", Engineering News-Record (11 November 1920) 925-927.

17. William Cowin died from consumption in either 1874 at the age of 49, or in 1875 at the age of 48. Death records for the town of Lambertville show that he pass~d away in May 1875. Nevertheless, the Lambertville Democrat newspaper printed no obituary or death notice for him in any issue during May or June of that year. Records for the Mount Hope Cemetery, in Lambertville, list his death in 1874 at the age of 49.

18.Snell, History of Hunterdon and Somerset Counties

Unpublished


Page 23

SELECTED BIBLIOGRAPHY

"Hunt's Mill, n.d." TMs [photocopy]. Clinton Historical Museum, Clinton, NJ.

New Jersey. Hunterdon County. Board of Chosen Freeholders. Minutes held by Hall of Records, Flemington, NJ.

Office of Engineer. Bridge Files, in Flemington, NJ

Town of Clinton. Minutes of the Council, in Town Hall.

Published

Fleming, R. "Sixty-Year-Old Iron Bridge in a New Jersey Village." Engineering News-Record, 11 November 1920, 925-27.

"Historical Facts on Lehigh River Floods Recalled in Lecture." Globe-Times (Bethlehem, PA), [May 1931].

"A Sweeping Flood. Widsespread Devastation. The Freshet in Clinton." Democrat (Clinton, NJ), 2 April 1869.

lowth~p truss bridge haer no. nj-19 on west main street

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