288 Improvement in the Construction of Bridges, &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-ny as was thought consistent with a just regard to strength 
and durability. Its execution was commenced in Decemer, 
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 cha’ 
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 assistan . 
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 /ateral strain upon piers or abutments ; an advantage 
that cannot be too highly appreciated in aqueduct bridges ; to 
completely avoid this lateral pressure, becomes immensely: impot- 
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 degre? 
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 connect 
with the top and side bracing. When the great facility and ease 
with which this kind of bridge is covered, is considered, in conne® 
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. s 
It may be stated most truly, that if most bridges were built 
with spans of 200 feet or over, there would be a much less nuim- 
