( -243 )

floor, above each cask, to receive them whennecessary.

A buoyancy of about 5800 lbs. will be suffi-cient for rafts, placed at the distance of twelvefeet between centres, for a bridge for fieldartillery, infantry in files, and cavalry by twos.Allowing about 1980 lbs. for the weight oftwelve feet of floor, as before, (see Rafts of Tim-ber,) there will remain a buoyancy of 3820 lbs.for each raft.

lbs.

The weight of infantry, crossing in file, is 2100Ditto of cavalry, by twos - 2032

The proportion of the weight of a light0 pr. which each float will have tobear, (see Timber Raft,) is - - 2007

A 9 pr. gun and carriage, without lim-ber, is about. 2850

But, leaving intervals between guns, this willpartly be supported by the adjoining rafts.

Suppose a bridge to be made with casksNos. 4, 0, 9, and 14, given in the table.

Wt. of casks.

44 casks No. 4, will float about 5852 lbs. 2008 lbs.

18

No. 0,

5904

1494

10

No. 9,

5080

1150

5

No. 14,

5885

795

For

raft, fig. 5

, (plate 7,) the casks

should be

lashed together by pairs, side to side, and a

h 2