Figure 22. — Bollman deck trusses in the North River Bridge built in 1873 at 

 Mount Crawford, Virginia, on the Valley Railroad of Virginia (B. & O.). 

 Each end span is 98 ft. 6 in.; the river span is 148 ft. 9 in. (Photo 756, 

 Baltimore and Ohio Collection, Museum of History and Technology.) 



such renowned engineers as Herman Haupt and M. C. 

 Meigs 



An interesting application of the system was in a 

 drawbridge, formed of two Bollman deck spans, over 

 an arm of the Mississippi at Quiney, Illinois (see fig. 

 17). The first iron bridge in Mexico was erected by 

 Bollman over the Medellin River about 1864. 

 Another work of this period, which attracted consider- 

 able attention, was a pair of bridges that Bollman 

 erected over North Carolina's Cape hear Rivei in 

 1867-1868. These bridges were notable for their 

 foundation on cast-iron cylinders, sunk pneumatically. 

 This was one of the first instances of the use of the 



process in America, and the depth of 80 feet below 

 the water surface reached by one cylinder was con- 

 sidered remarkable for years afterward. 



In the last active decade or so of his career, Bollman 

 produced hundreds of minor bridges and other struc- 

 tures. In 1873 he supplied the castings for the splendid 

 iron dome of Baltimore's City Hall and erected the 

 ingenious water-main truss which carries Lombard 

 Streel over Jones Falls in that city. In this structure 

 the top and bottom chords of the central line of 

 trussing are cast-iron water mains, bifurcated at the 

 abutments, and joined by cast- and wrought-iron 

 web members (see fig. 20). 



96 



BULLETIN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



