C 21Q HYDRAULICS. 



the plate n, which is ground very flat, so as to 

 apply accurately to the whole circumference of 

 the orifice. This plate is called the regulator, or 

 steam-cock, and it turns horizontally round an 

 axis, o, which passes through the top of the boiler, 

 and is fitted by grinding to the socket, so as to be 

 steam-tight. It is opened and shut by a handle 

 fixed to its axis. 



In the cylinder b is a solid piston, p, well fitted 

 into it, and made air-tight by a packing of leather 

 or soft rope, well filled with tallow ; and for greater 

 security, a small quantity of water is kept above 

 the piston. 



The piston-rod dis suspended by a chain, which 

 is fixed to the upper extremity of the arched head 

 e of the great lever, or working-beam, e f g, which 

 turns on the gudgeon f. There is a similar arched 

 head g, at the other end of the beam, to the upper 

 extremity of which is fixed a chain, carrying the 

 pump-rod h, which raises the water from the 

 mine. 



The load on this end of the beam is made to 

 exceed considerably the weight of the piston at 

 the other extremity. 



At a small height above the top of the cylinder, 

 is a cistern called the injection-cistern, i. From 

 this descends the i?ijectio?i~pipe, h 9 which enters 

 the bottom of the cylinder, and terminates in a 

 nozzle pierced with holes. This pipe has a cock, 

 /, called the injection-cocli. 



At the opposite side of the cylinder, a little 

 above its bottom, there is a lateral pipe, m, turning 

 upwards at the extremity, and there covered by a 

 clack-valve, called the snifting-valve, which has a 

 little dish round it, to hold water for keeping it 

 air-tight. 



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