Chap. XXVII.

CANAL AND RIVER LOCKS.

1553

The capstan used at the basin of Dunkirk willgive some idea of a simple arrangement for thepurpose of hauling the boats from the reservoirinto the stream of the canal: upon a platform oftimber on the quay, an upright post is turned byhandspikes, which coils the rope around it.

The profile of a capstan executed at Cherbourgshows a nut pierced to receive an iron rod 4 inchessquare, set 5 feet in the side of the lock-walls,where it is held firm by two long arms termi-nating in the form of a T; this arrangement is themost simple, and not so likely to decay as thetimber framework. The upper portion of the lockor fore bay is the usual position for the capstan;the tail bay of locks sometimes also requires onewhere the canal communicates with the ocean.

Iron Lock Gates at the Wet Dock at Montrose. —The frames are of cast-iron, and entirely coveredon both sides with wrought-iron' boiler-plate:where they are placed the entrance is 55 feet widein the clear, and the centre of the heel-post is 1 footwithin the face of the wall, the distance betweentheir centres being 57 feet: the height of the gatesis 22 feet 6 inches; they point 10 feet, and their ribshave a curvature on the hollow side of 18 inches.The heel-posts are 21 inches in diameter, and inform a little more than a semicircle; after castingthey were turned in a lathe: the thickness of themetal is 1^ inch ; they each fit into a cast-ironsocket, and work on an iron gudgeon 10inches in diameter, cast on a sole-plate 4 feet6 inches long, 21 inches wide, and 2 inchesthick; this is dovetailed and riveted firmlyinto the stone, and afterwards so keyed asto press the heel-posts into the quoins,which are of Kingoodie stone, polished asnearly to the circle as possible, and thestone and iron are in such close contact, thatthe water is effectually prevented from pass-ing throughout any portion of their height.

The mitre posts are 18J inches in breadth,

1 j inch thick : holes are cast in them forthe introduction of the iron bars, of whichthere are eleven to each leaf, 2 inches thick,

Fig. 2891.

CAPSTAN.

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Fig. 2892.