1394

THEORY AND PRACTICE OF ENGINEERING.

Book II.

Fig. 2317.

DHIDGE OF BOATS.

'_ 1 . ..

Fig. 2318.

BKJDGB OP BOATS.

the effect of the waves breaking over. The roadway is cross-battened, to prevent the cattlefrom slipping, and the sides are fenced in : the drawbridges are suspended by two three-quarter-inch chains, one of which forms a guard-rail, and the other passes through theengine-house, where it is connected with a small purchase machine. This bridge at thetime of low-water is passed in 7 minutes, and at high-water in 8, at a spot where theHamoaze is 2550 feet wide at high-water, and 2110 at low, the greatest depth being 96feet, and at low-water 18. 'Hie current at the ordinary spring*tides runs from 260 feet per