Trail Bridges

—When the river is not more than 150 yards wide, a sheer-line may be used in place of the anchor and cable; the sheer-line must be taut enough to keep above water. If the banks are not high enough, the sheer-line should be elevated at each shore by pa ing it over a frame formed by three poles, arranged like an artillery gin. Upon this line a pulley is fixed, so that it can run freely from shore to shore; through the eye of the pulley-block a line is pa ed, one end of which is attached to the bow of the first, and the other to the bow of the second, boat forming the raft. The raft is manœuvred in the same manner as the flying bridge; or one end of a line may be made fast to the running-block on the sheer-line, while the other pa es through a snatch-block near the stern of the raft on the up-stream side; by hauling in or letting out this line the proper direction is given to the raft.