HYDRAULICS. 223 



Fig. 47. is Mr. Cartwright's steam-engine, the 

 construction of which evinces much ingenuity, a 

 is the cylinder, which is supplied with steam from 

 the boiler through the pipe b; c is the piston in 

 the act of going up ; d is the pipe that conducts the 

 steam into the condenser e, which consists of two 

 cylinders, one within the other, leaving a small 

 space between them, into which the steam is ad- 

 mitted; while the inner cylinder is filled with cold 

 water, and also the external cylinder surrounded 

 by the same ; so that, by this means, a very large 

 surface of steam is exposed, though no water is 

 suffered to come into actual contact with it. 



To the bottom of the piston, c, is attached a rod, 

 with another piston, e, working in the pipe d. 

 When the piston e arrives at the bottom of the 

 cylinder, a valve which is in the piston, is opened 

 by its pressing against the bottom, and opens a 

 communication with the condenser, whilst the 

 spring k, fixed to the rod of the piston, shuts the 

 valve which admits the steam from the boiler. 

 The steam, therefore, being thus condensed, runs 

 into the lower pipe f. The piston e arriving at 

 the bottom of the pipe in which it works at the 

 same time with c, presses upon the condensed 

 water, shuts the valve f, and forces the water up 

 the pipe g> into the box h. The air which is dis- 

 engaged from the water rises to the top of the box, 

 and, by its elasticity, forces the water through the 

 pipe i, which carries it back again into the boiler. 

 When the air accumulates in the box to such a 

 degree as to depress the water, the ball-cock falls 

 with it, and opens a valve in the top of the box, 

 which suffers some of the air to escape. 



When all the steam is condensed, the motion of 

 the fly attached to the machine brings the piston 



