SLIPWAYS. 



325 



according to the weight and position of the vessel on the ways, 

 the cross-head is pushed up, forcing the ram into the retaining 

 cylinder, and drawing up the links. On reversing the valve- 

 lever, the pressure is shut off, and the main cylinders opened to 

 exhaust, so that the constant-pressure ram reverses the stroke, 

 forcing in the main rams and -pushing down the links to the 

 position from which they started. A definite upward and 



FIG. 322. 



downward travel, equal in length to the stroke of the rams, can 

 therefore be given to the links by the forward and backward 

 movement of the hand-lever. The links are jointed together 

 with rectangular flat plates, and as all links and plates are made 

 of equal length, it follows that if suitable pawls are fixed to the 

 cradle, and arranged to gear with the ends of the joint-plates, the 

 cradle will be drawn up at each upward stroke of the rams, while 

 during the downward motion of the links the pawls will slip, 



FIG. 323. 



the cradle remaining in its highest position, being held by the 

 pawls in gear with the rack cast on the centre line of rails. The 

 hauling-pawls, of which several sets are used, are made of forged 

 iron, secured to the main rib by cast-steel or malleable cast-iron 

 brackets. With this system, no disconnections or removal of 

 links or bars is required. The only loss is the time occupied in 

 the return stroke, which, however, is not great, as, owing to the 



