( 237 )

by all these combinations, was forced rapidlyback upon Celirico and Guarda.

Bridges of Casks .

After what has been said of the constructionsof bridges of pontoons, boats, and rafts of timber,it will only be necessay to consider casks as totheir powers of buoyancy, and formation intofloats ;* the other parts of the construction being-completed much in the same manner as in theformer cases.

The ordinary rule for calculating the contentsof casks, is founded upon the supposition thatthey are made up of two conic frustra.

Thus, to determine the quantity of water dis-

placed by a cask whosebung diameter is 34 in.;head diameter 27 ; andlength 50 in. outsidemeasure:

* When Maximus declared himself Emperor , and was

fastening to Rome , he passed a river near Aquileia on a bridgeformed of empty wine casks.— Ilerodianus, chap. iii. book 8.

The Aide Memoire observes, page 1076, “ that bridges ofcasks will only serve for infantrybut whatever possessespower of buoyancy, may be applied on any scale.

Vegetius mentions bridges of casks in his Treatise de ReMilitari.