OF HYDRAULIC ENGi ' 135 



the water that it rises through the valve H, along the LECT 

 pipe J\l M, into the air-vessel K K. '^^.^~* 



The higher that the surface of the water H is raised 

 in the air-vessel, the less space will the air be condensed 

 into, which before filled that vessel ; and therefore the 

 force of its spring will be so much the stronger upon 

 the water, and will drive it with the greater force 

 through the pipe at F: and as the spring of the air 

 continues whilst the plunger g is rising, the stream or 

 jet S will be uniform, as long as the action of the plun- 

 ger continues : and when the valve b opens, to let the 

 water follow the plunger upward, the valve a shuts, to 

 hinder the water, which is forced into the air-vessel, 

 from running back by the pipe MM into the barrel of 

 the pump. 



If there was no air-vessel to this engine, the pipe 

 G HI would be joined to the pipe MM N at P; and 

 then, the jet S would stop every time the plunger is 

 raised, and run only when the plunger is depressed. 



Mr. Neu-sham's water-engine for extinguishing fire, 

 consists of two forcing-pumps, which alternately drive 

 water into a close vessel of air ; and- by forcing the 

 water into that vessel, the air in it is thereby condensed, 

 and compresses the water so strongly, that it rushes 

 out with great impetuosity and force through a pipe 

 that comes down into it ; and makes a continued uni- 

 form stream by the condensation of the air upon its 

 surface in the vessel. 



By means of forcing-pumps, water may be raised to 

 any height above the level of a river or spring ; and 

 machines may be contrived to work these pumps, either 

 by a running stream, a fall of water, or by horses. Aii 

 instance in each sort will be sufficient to shew the 

 method. 



First, by a running stream, or a fall of water. Let A A 

 (Plate III.) be a wheel, turned by the fall of water B B; 

 and have any number of cranks (suppose 6) as C, D, E, F. 



