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The oldest stone arch railroad bridge in the 

world, built at Relay, Md. r in 1835, still 

bearing heavy B. fy O. traffic after 89 years 

of continuous service 

This paper is respectfully dedicated to the early engineers 
of the Baltimore and Ohio Hailroad Company, pioneers in American rail- 
road construction and men whose achievements are resplendent with great 
ace ompl i shment s • 

The author wishes to express in full measure his appreciation 
of the assistance received from the Baltimore and Ohio Railroad through 
Mr. £. J3. Kennedy, Valuation Engineer, without whose aid this paper could 
not have been written. 




The Thomas Viaduct, which spans the picturesque valley of 
the Pa tap sco River at Belay, Maryland, is unique in many ways* It has 
the distinction of being the oldest stone arch railroad bridge in the 
world and is one of the few masonry viaducts that are constructed on a 
curve instead of a tangent. It is with these and other more important 
features of this early accompli ahment of American engineers that this 
paper is chiefly concerned. 

The history Of the Thomas Viaduct rightfully begins in 1833 
when the list Of estimates for masonry on the new lateral railroad from 
Baltimore to Washington included as its first and most important item 
the data on a bridge to carry the tracks across the Patapsco at Relay. 
A structure of eight arches, each of 58 foot span, with the roadway 66 
feet above the surface of the water was called for. It was calculated 
that for the stonework 20,000 perches of 25 cubic feet would be required, 
that the price per perch would be $ 6*00, and that the net cost would be 
$ 120,000. 

The bridge was designed by B. H. Latrobe, an assistant engi- 
neer in the employ of the Baltimore and Ohio Company, who had played an 
important part in the survey of the Washington Branch and had submitted 
the estimates. After the specifications had been approved by the direc- 
tors, the contract was awarded to John Mo Gartney of Ohio. Work was start- 


ed on the 4th of July, 1833 and completed on the 4th of July, 1635 > It 
was properly named the Thomas viaduct in honor of the first president of 
the road* 

Records of the bridge during the period of construction are 
entirely lacking and the original designs and working drawings are not 
available. The structure as it now exists is essentially the same as it 
was in 1835 , ami by a survey of its present dimensions and details of 
construction a comprehensive impression may be obtained of the magnitude 
of the work so ably executed by these early pioneers in the new field of 
railroad building. 

The following data on the Viaduct was obtained from the of- 
fice of the Bridge j£ngineer of the Baltimore and Ohio Railroad Company. 
The structure is built on a curve 4 degrees and 23 minutes to a line go- 
ing west and has a .14 % descending grade, also going west. Its total 
length is 612 feet and the width is 23 feet 4 inches, out to out. The 
height from the ground to the parapet la 54 feet, The eight spans have 
lengths varying from 57 feet 10£ inches to 58 feet 4^- Inches. The bridge 
carries a double track roadway which has a superelevation of 5§ inches* 
The approach curves are both sharper curves than that of the bridge and 
the spaed is limited to about 30 miles an hour. On the upstream or con- 
vex Bide there is a foot path which overhangs the exterior wall and is 
enclosed by a strong iron railing. 

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The stones are all of Maryland granite obtained from the near- 
by quarries in the valley of the Patapsco. The work is of a rustic nature, 
that is, the stones are dressed around the edges and left rough and un- 
hewn in the center* 

It is interesting to note in this connection that one of the 
officials strongly opposed the use of this style of masonry* This indi- 
vidual would not waive his objections until Contractor Kc Cartney, who 
was then building the Patterson Viaduct on the old main line," to ok the 
trouble to erreot at the quarry a wall in which the expanse and appear- 
ance of the rustic work was contrasted with that of dressed or faced 
work, obviously to the disadvantage of the latter*" 

The arches are supported on large stone piers* The security 
of the foundations is beyond doubt, for the entire valley is of a rocky 
formation and the location of bed rock was probably a comparitively 
sasy task* The arch stones are in the form of a ring 2 foot 6 inches 
thick with stone fillers over each pier* The 1 foot 6 inch stone slabs 
under the roadbed are supported by number of 12 inch brick walls, 4 feet 
apart, which rest on the stones of the arches, these hollow colums have 
the appearance when the roadway and covering slabs are removed of a honey 
ctftnb of brick chimneys* The vertical granite walle ore 2 feet 6 inches 

The instructions issued ta the contractors in 1833 by Casper 

Wever, Superintendent of Graduation and ilasonry, contained the follow- 
ing articles: 

"(1) ill masonry in the bridge shall be of a rubble character 
excepting the face work of the abutments and the sheeting of the arches, 
and shall be well laid in good motar. 

(2) The faces of the abutments shall be rough in their exter- 
ior* but the stone shall be ranged and dressed bed and top, and have ver- 
tical joints. The sheeting stone shall be cut or shaped so as to range 
transversely of the arch, and conform to the radii of the circle or cir- 
cles of which the arch may be a segment. 

(3) No ardent spirits are to be kept or used near the work," 
These specifications, with the probable exception of the last one, ware 
strictly observed by i*c Oartney in the building of the Thomas Viaduct* 

The ease with which the stone was procured from the quarries 
of the Patapsco on the line of the railroad did much to moderate the ex- 
pense of construction* The final total cost of the bridge was $ 128,260.20. 
Although the prices were different for the various kinds of stone work, 
it is probable that the average was about 4 6.00 per perch of 25 cubio 
feet* that is, almost a cubic yard. The cost of earth work at that time 
was about % 0.25 per yard. The above price includes 4 6,000.00 for 4,000 
perches of rubble stone deposited around one of the abutments and some of 
the piers for securing the foundations more firmly. Deducting this amount 


from the above figure brings the final cost 4 2,260.00 of the original 


estimate for net cost submitted by latrobe. The total amount of stone 
used was 19,604 perches* the estimated amount 20,000 perches. The slight 
differences reflect well upon the ability of the designer to estimate 
the cost of masonry construction* 

In engineering works, however, the inital cost is not always 
of the greatest importance. The lack of upkeep expenses on the Thomas 
Viaduct has been one of its most remarkable features. During 89 years of 
c ominous service under the heaviest of traffic, only a minimum amount 
of repairs have been necessary. In the arches, some of the stone 3 which 
had settled slightly were Jacked back in place and secured with cement. 
The three sections of brick columns which support the section of the road- 
way directly over each pier have been filled with concrete. These slight 
alterations have rendered the viaduct fully as strong as it originally 
wes. It is the opinon of the engineers of the Baltimore and Ohio Hail- 
road that the structure will stand with out alteration for many more years 
unaffected by either the elements or the annually increasing loads which 
it must bear many times each day* 

After a consideration of the fact that this viaduct, almost a 
century old, and designed for engines less than five tons in weight new 
supports the modern thirty ton locomotives and is capable of upholding 
still greater loads, the question naturally arises as to whether it was 
the intentions of the designer to builiso strong a structure. 



It is not probable that young La trobe was fully cognizant of 


the vast capacity of his bridge, nor is it likely that even in his most 

imaginative moods he could have even partially visualized the stupendous 
increase iamw in the weight and size of railroad rolling stock. It 
must be remembered that at that period the design of bridges w^s not the 
exact science of this age and that the construction of railroad bridges 
was a new field in which no precedents or rules to be followed* 

That permanency was desired by the directors of this first 
.American railroad can easily be demonstrated* Some of the early bridges 
and culverts had been built of wood and by 1633 the company had been 
thoroughly impressed, as the following statement from the Seventh An- 
nual Report to the Stockholders reveals, with the necessity of elimi- 
nating as far as possible upkeep expenses. 

**In the construction of the Washington Road, the board hud 
regard to its durability, not less than to making it a source of immed- 
iate profit to those interested in the undertaking. True economy consists, 
in the first place, in constructing the road so as to obviate the neces- 
sity of frequent repairs, and to enable the motive power to be employed 
to its fullest effects without injury to the bridges or roads over which 
it passes in the performance of its dally work* The board have, there- 
fore, caused all viaducts to be built Of stone of the most permanent yet 
simple construction." 

That the employees of the road were well satisfied with the 
structure is brought out in the report of johnathan Knight, Chief Engi- 


ne a r of the Road. 

"The massive materials of which the Thomas Viaduct is built, 
the care that has been taken in putting them together, and their founda- 
tion on solid rock, are guarantees of its continuing durability." 

This assurance was, however, by no means universal during the 
two years of construction* The design met with much opposition and many 
engineers expressed aoubt of its stability* The bridge was often referred 
to as "latrobe* s Folly." notwithstanding this, he persisted, and time 
has fully justified his faith in himself and his bridge. 

B* H- Latrobe, the designer of the Thomas Viaduct, came from 
a family of no mean accomplishments. It included a noted writer, the 
architect of the Capitol Building at Washington, and the first cor- 
poration counsel of the Baltimore and Ohio Hailroad. Latrobe was edu- 
cated for a lawyer but soon found that his inclinations ran in a counter 
direction, sni being already a skillful draughtsman and an accomplished 
mathmatecian he obtained employment as an assistant engineer. His com- 
mendable record in the early surveys ^nd designs enabled him to succeed 
Jonathan B. Knight, Chief Engineer of the Baltimore and Ohio during the 
first fourteen years of its existence. 

John Mc. Cartney of Ohio the contractor who erected the Thomas 
Viaduct was favorably known to the stockholders of the company as the 
builder of the Patterson Bridge on the old main line. He was an ardent 
advocate of the rustic type of masonry. The contractor was vary proud of 


his part in the building of what was then the largest structure of its 
kind in the United otates and ha expressed his feelings in two distinctly 
different ways. The following synopsis of an article from "The Broadside," 
one of the early single sheet newspapers of Baltimore, reveals how the 
people of that city reacted to the I'irst of these expressions. 

"Mc. Gartney, the builder of the Viaduct over the Patapsco, 
gave a frolic at the closing of the arches, jsfter the men were made drunk, 
he ordered them to kneel before him, and in that situation baptised them 
by pouring on their heads a pint of whiskey, This violation of the Holy 
Bites of religion took place on the Baltimore and Ohio Railroad in the 
vicinity of Sllicot Mills, the office of his warm friend and supporter^ 
the superintendent of the road, being in the distance." 

In order to perpetrate his connection with the work as well us 
that of the original projectors and directors of the road, Contractor 
Mo. Cartney had errected at his own expense, at the abutment near the 
Belay House, a granite obelisk. The shaft is about 15 feet in height and 
pyramid ical in shape. On each of the four sides are suitable inscriptions 
giving the a_tes of construction and the names of those associated with the 
building of the viaduct. Hear the bottom in small and mode3t letters 
appears the statement that the monument was errected by John Mc. Cartney. 

The importance of the Thomas Viaduct was not coafined to the 
early years of its existence. During the Civil ffar the bridge was a 

point of paramount military value, for the cars of the Pennsylvania were 


then running on the Baltimore ond Ohio tracks and all the railroad traffic 
to stations below Baltimore had to pass over the viaduct* 

In order to frustrate any attempt of the Confederates to 
destroy the bridge , a detachment of soldiers guarded it night and d^y and 
forced all pedestrian! to cross the river over the bridge on the Washington 

The real signifigance of the Thomas Viaduct lies, however, 
not in its former military importance nor its present commercial value*, 
but in the splendid tribute it pays to the skill, the ability **nd the 
indomitable perseverance of those early American engineers who were pioneers 
in a new fie 14 of endeavor and who recongiaed no such word as failure. 



The information contained in this thesis was gathered, from 
the following sources. 
1* The Annual Eeports to the Stockholders of the Baltimore and Ohio 

Eailroad. 1828-1 630 
2. A Bibliography of the Baltimore and Ohio Eailroad, 1827-1879 

John W. Lee 
3* Narrative of the Proceedings of the Board of Engineers of the Balti- 
more and Ohio Eailroad 

Long and Mc Kiel 
4* History and .Description of the Baltimore and Ohio Eailroad 
William Prescott Smith 

5. B and Magazine for November 1921 

6. Eambles in the Path of a steam Horse 

Sli Brown 

7. The Office of the Bridge Engineer of the Baltimore and Ohio Bail- 
road through the kindness of Mr* Kennedy. 

Type of engine and «r for which the Thomas Viaduct was designed 


This is a B. $ O. freight car of 188%— 
tke first operated by the road 


This is a reproduction of an old print 
of Peter Cooper's "Tom Thumb," the 
first locomotive of the Baltimore 4" Ohio 
Railroad, which was built in this 
country in 1830 

Type of engine now in use 

Quite in contrast to the "Tom Thumb" is 

this modern coal-burning Baltimore fy Ohio 

passenger engine of today 

MO Gartney's Monument