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be over both gunwales, 4 over each, which willstrengthen the bridge.

The men carrying chesses pass up on oneside of the bridge, deliver them to the artificersappointed to lay them, and return in succession.The gang-boards are then placed over the endsof the chesses, and lashed through holes ornotches in them to the balks, to keep all steady.

With a well arranged train of pontoons, andexpert pontoneers, the time required to con-struct a bridge is at the rate of minute foreach pontoon.

When the bridge is constructed, a thin layerof sand or straw may be thrown upon the floor.

In passing a pontoon bridge, no carriages orhorses should be allowed to cross with infantry:horses should be walked over; cavalry shoulddismount, and cattle should be made to passsingly; for they press so much on each otherthat they woidd perhaps destroy the bridge.

If a bridge of pontoons is to be laid over atide river, strong cables should be stretchedacross, at each end, and the pontoons anchoredfrom head and stern; and further precautionswill be necessary to prevent the bridge frombeing injured at low water. But rivers of anyconsiderable magnitude are liable to agitationsnear their mouths, (where tides most affect