There had never been any question about the many serious inadequacies of
wood as a bridge material. Decay and fire risk, always present, were the
principal ones, involving continuous expenditure for replacement of
defective members and for fire watches. It was, in fact, understood by
the management and engineering staff of the B. & O. that their timber
bridge superstructures, though considered the finest in the country,
were more or less expedient and were eventually to be replaced. In this
regard it is not surprising that Latrobe, a man of considerable
foresight, had, at an early date, given serious thought to the possible
application of iron here.
[Illustration: Figure 10.--POTOMAC RIVER CROSSING of the Baltimore and
Ohio at North Branch, Maryland, built in 1856. There are three Bollman
deck trusses. (_Photo courtesy of Baltimore and Ohio Railroad._)]
[Illustration: Figure 11.--THE FINK TRUSS. (_Smithsonian photo
41436._)]
[Illustration: WENDEL BOLLMAN'S
Patent Iron Suspension Railroad Bridge.
The undersigned would inform the officers of Railroads and others, that
he is prepared to furnish Drawings and Estimates for Bridges, Roofs,
etc., on the plan of Bollman's Patent.
The performance of these bridges, some of which have been in use for six
years, has given entire satisfaction. Their simplicity of construction
renders repairs easy and cheap, and by a peculiar connection of the Main
and Panel Rods at the bottom of the Posts, all danger from the effects
of expansion, which has heretofore been the chief objection to Iron
Bridges, is entirely removed.
J. H. TEGMEYER,
Baltimore, Md.