60 Experimental Philosophy. [Lecture 5. 



The most powerful forcing pumps, however, 

 are wrought by steam engines, for steam is one 

 of the strongest powers in nature. The steam 

 engine consists of a large cylinder or barrel, in 

 which is nicely fitted a solid piston, like that of 

 a forcing pump. The steam is supplied from a 

 large boiler close by, and is admitted into the 

 cylinder by an orifice, which can be occasionally 

 shut. The force of the steam lifts the piston, to . 

 the top of which is affixed a long lever to work a 

 forcing pump, or for any other purpose; and 

 when the piston is lifted a certain height, it 

 opens a small valve in the bottom of the cylinder, 

 through which a small quantity of cold water be- 

 ing admitted the steam is condensed, and thus a 

 vacuum being created, the piston again descends, 

 and is again lifted up by the force of the steam. 

 For a detailed description of this invaluable en- 

 gine, however, our readers must consult the En- 

 cyclopaedias or Pantologia, and our best treatises 

 on Mechanics. 



