THE STEAM-ENGINE. 



429 



cessary to elevate the piston of a pump, loaded with the column of water which 

 it raised. The following, then, is a description of the improved engine of Watt, 

 by which such work was proposed to be performed : — 



Fig. 8. 



i 



?*<*- 



T~T 



1 , 1 , 1 



XTT 



In the cylinder represented at C (fig. 8), the piston P moves steam-tight. 

 It is closed at the top, and the piston-rod, being accurately turned, runs in a 

 steam-tight collar B, furnished with a stuffing-box, and is constantly lubricated 

 with melted tallow. A funnel is screwed into the top of the cylinder, through 

 which, by opening a stop-cock, melted tallow is permitted from time to time to 

 fall upon the piston within the cylinder, so as to lubricate it, and keep it steam- 

 tight. Two boxes, A A, called the upper and lower steam-boxes, contain 



