f 



486 



THE STEAM-ENGINE. 



use, yet it is so simple and elegant in its structure, and forms a link so inter- 

 esting in the history of the steam-engine, that some explanation of it ought not 

 to be omitted in this work. 



The steam-pipe from the boiler is represented cut off at B, fig. 47 ; T is a 



Fig. 47. 



spindle-valve, for admitting steam above the piston, and R is a spindle-valve 

 in the piston ; D is a curved pipe forming a communication between the cyl- 

 inder and the condenser, which is of very peculiar construction. Cartwright 

 proposed effecting a condensation without a jet, by exposing the steam to con- 

 tact with a very large quantity of cold surface. For this purpose, he formed 

 his condenser by placing two cylinders nearly equal in size, one within the 

 other, allowing the water of the cold cistern in which they were placed to flow 

 through the inner cylinder, and to surround the outer one. Thus, the thin 

 space between the two cylinders formed the condenser. 



The air-pump is placed immediately under the cylinder, and the continua- 

 tion of the piston-rod works its piston, which is solid and without a valve. F 

 is the pipe from the condenser to the air-pump, through which the condensed 



