C 248 )

other floating bodies, as recommended by M.Folard *

In the Aide-Memoire, page 1253, we find thefollowing mention of a raft or bridge of air-tight cases made of light planks, proposed byan engineer of Cambrai , named Hermann, in1719. The cases were each 5 feet long, 1 footdeep, and one foot broad; divided into fourcompartments, by interior partitions, for thedouble purpose of preventing one leak fromfilling a whole case, and of giving it strength toresist the outward pressure. Four of thesecases lashed together formed one raft. Eachcase weighed about 75 lbs. To make a bridgefor infantry,—the first case being put into thewater and pushed off to make room for another,the second was launched, and connected withthe first by clamping together the ends of thebeams or baulks attached to each. Both cases,so connected, were then pushed outwards, togive place to the next set; proceeding in thismanner, to prolong the communication till com-pleted, and sustaining the rafts against the cur-rent, by ropes to the banks. The weight of a raftcomposed of four cases of these dimensions wasabout 300 lbs. The weight of water displaced

* Folard on Polybius, vol. iv. page 5G; plate iv, andesprit de Folard.