288 Improvement in the Construction of Bridges, S^c. 



their fitting surfaces ; but on the showing faces of each pier, the 

 stone is rough as it came from the quarry. 



The whole structure was designed with a view to as much 

 econo v.y as was thought consistent with a just regard to strength, 

 and durabihty. Its execution was commenced in Decem >< r, 

 1836, and the work was finally completed on the 5th of Septem- 

 ber, 1838, at an expense of about $110,000. I doubt whether 

 any bridge of the same gigantic dimensions and substantial char- 

 acter, composed of such choice materials and rare workmanship, 

 has ever been constructed at a smaller expense. This work was 

 projected by Moncure Robinson, Esq., chief engineer, and exe- 

 cuted under the direction of himself and his principal assistant. 

 The work itself stands like a mighty Colossus, bestriding the 

 ancient Powhatan, destined to hand down to posterity both itself 

 and its authors ; and those piers of imperishable granite will re- 

 main as proud monuments, to remote generations of the present 

 State of Virginia, and her sons, as connected with the sciences 

 and the mechanic arts. 



This improvement possesses the very important advantage of 

 exerting no lateral strain upon piers or abutments ; an advantage 

 that cannot be too highly appreciated in aqueduct bridges ; to 

 completely avoid this lateral pressure, becomes immensely impor- 

 tant in their cost and safety. This mode of construction is per- 

 fectly suited to the purposes of aqueduct bridges, as well as all oth- 

 ers, especially for railroads ; it being continued horizontally, and 

 admitting, in the principle and practical execution, of any degree 

 of strength that may be required, for any span which is practica- 

 ble under any circumstances ; it also presents the advantage of 

 having the trunk or canal so suspended, as to preclude all possi- 

 bility of self-destruction, by the leakage coming in contact with 

 any of the important timbers, besides rendering other facilities, of 

 the greatest importance in the mechanical execution, as connected 

 with the top and side bracing. When the great facility and ease 

 with which this kind of bridge is covered, is considered, in connec- 

 tion with other advantages, its adoption for all purposes of bridges, 

 aqueduct bridges, railroad bridges, canal bridges, &c., is beyond all 

 question desirable, as the strongest, most durable, and by far the 

 cheapest mode of construction, and to keep in repair. 



It may be stated m.ost truly, that if most bridges were built 

 with spans of 200 feet or over, there would be a much less num- 



