28

Tons*

Brought up - 164

The force of hurricane winds, being49.2 lbs. per foot superficial onthe road; viz. 560 X 30 = 16800.

surface of the road:

16800 X 49.2 lbs. = 369 tons. 369Oxen, infantry, cavalry,* or other

things passing at one time - - 300

Weight of the road to be suspended.

See the Report. - -■ - - - 342

Whole weight suspended from the

two points - - - - -1175

s 738.5 tons, the strength of the cables col-lected ; derived as follows :

A bar of iron, inch square, acted upon in a perpen-dicular direction, at a mean of eight experiments, madeat Captain Browne’s Manufactory, Mill-Wall, Poplar,broke with 25 tons. One-fourth the breaking strength f,

* Though by 49 sec. of the act 59 Geo. 3. cap. 48.the number of oxen and neat cattle is limited to 20 onthe bridge at one time, yet the number of cavalry andinfantry is not nor could be limited. It cannot be sup-posed that 5000 soldiers on a forced march would bedelayed five hours in passing this bridge.

f Mr. Emerson thinks one-fourth the breaking strengthshould be taken as the practical strength. Mr. Rennie(3d Report, Menai Bridge, 29th April, 1819, page 27.)says, “ I have before stated, that I consider a bridge,15