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ference to any other, for military bridges, is amatter which will no doubt receive all the cau-tion and consideration, which such a questionmerits, in the experiments which, it is understood,are about to' be made, under the direction of thecommittee of experienced Artillery Officers, towhich this matter has been referred; and whowill, probably, he directed to revise and reportupon the whole system of pontoons, and all thearrangements of our bridge equipments.

For these experiments, cylindrical vesssls havebeen prepared, of shape and dimensions nearlysuch as given in the table, page 251. The length22 feet, the diameter 2 feet 8 inches. Prefer-ence appears to be given to tin for covering,and spherical ends are considered better thanthe conical shape. Calculating the quantity,and weight of materials, in the framing, partitionsand covering, the weight of a cylindrical pon-toon of the above dimensions and material, isabout 4 cwt. Two of these are connected witheach other, to form one raft. The weight of theconnecting beams, and other appertenances, issomewhat greater than for the ordinary pon-toon, and may be taken at about 17 cwt. Theheight of the carriages is alike in both cases,Uamely, 12 cwt. 3 qrs. (page 33.)