Chap. XXIII.

TIMBER BRIDGES.

1385

Fig. 2289.

PLAN OF RICHMOND BRIDGE.

PLAN UNDER PLATFORM,

Fig. 2*291.

PLAN OF RICHMOND BRIDGE.

Bridge over the Schuylkill , at Fairmount, near Philadelphia , was designed by LouisWernwag , and destroyed by fire in 1838 : it was a beautiful piece of carpentry, composedof a single arch, the span of which was 340 feet, and it had no other support than that of

Fig . 22S2 BRIDGE OVER THE SCHUYLKILL.

the two abutments ; the versed sine was 38 feet, and the breadth of the carriage-way 30 feet.The principal timbers, which were of large dimension, were all sawn down the middle, forthe purpose of ascertaining whether they were perfectly sound; and when applied to thebridge they were placed at a sufficient distance apart to allow the tenons of 29 king-posts,