I igure 23, I in 1 )\i \ si K\ i\ lv. lim.i man iri ss hri»c;i . .11 S.i\-.il;<-. Maryland. 

 I lit- bridge was built elsewhere in 1852 and was moved to this now -abandoned 

 Baltimore and Ohio industrial siding in about 1888. 



hi the mid 1870's Bollman saw his truss pass into 

 obsolescence. This was due primarily to the generally 

 increasing distrust of cast iron for major structural 

 members due to its brittleness, but advances in struc- 

 tural theory, availability of a greater variety of rolled 

 structural shapes, and the increasing; loading patterns 

 of the period all contributed. 



Although no Bollman trusses were built by Bollman 

 or the B. & O. after 1875, those in use were only 

 removed as required by heavier motive power. The 

 Harpers ferry span, as noted, remained in full main- 



line service until 1894. Bollman trusses on feeder lines 

 were continued in use until much later; .1 number of 

 them on the Valley Railroad of Virginia (see fig. 22) 

 were not removed until 1923. However, only on the 

 most isolated spurs was the Bollman truss permitted 



ich really ripe age. The sole known remaining 



example (fig. 2 i) stands on Mich a branch — ironically, 

 at Savage, over the Little Patuxent, the site of the 

 first Bollman -pan. This is not the 1850 bridge, but 

 one built in 1852 and moved to the present site 30 

 years later. The fate of the first span is not known. 



PAPER 36: ENGINEERING CONTRIBUTIONS OF WENDEL BOLLMAN 

 L'Jl 527 67—7 



97 



