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at their greatest immersion, being about 1,250lbs., the buoyancy of each raft was thereforeabout 950 lbs.,—sufficient only to support in-fantry marching in single file.

Excepting for convenience in transport, itWould be a waste of means to provide smallcases like these, for constructing a raft or bridge;for a boat, capable of displacing a much greaterquantity of water, than the raft formed of fourcases, might be made with fewer materials :—all small vessels are made up of more material,than larger ones, in proportion to their volume.

Twenty of these cases put together, wouldform a raft twenty feet long, five broad, andone deep, having a buoyancy of about 4,750 lbs.,which is nearly equal to a large tin pontoonsunk eleven inches. Rafts such as these, placedfive feet asunder, would therefore suffice fora bridge for cavalry in single file, infantry indouble file, and artillery unlimbered.

A slight frame of deal, 20 feet long, 2 broad,and 1 deep, covered with tin, would form a verybuoyant vessel. Such cases, laid parallel toeach other, at one or two feet asunder, con-nected by baulks, and covered with lightplanks, would form a safe bridge for infantry,and an excellent raft might be made with them:for, as has been observed with respect to casks,not being liable to fill, they may safely be