262 OUTLINES OF NATURAL PHILOSOPHY. 



ficient force be applied. This is called the Forcing 

 Pump. 



The Lifting Pump is in principle no way different 

 from the Sucking Pump. 



354. The discharge of water by pumps, though 

 naturally intermitting, may be rendered continual 

 by the elasticity of the air condensed in what is 

 called an air-vessel. This contrivance is represent- 

 ed in fig. 25. 



See DESAGULIER, Course of Experimental Philosophy, 

 vol. n. p. 152., 3d edition. MUSCHENBROEK, 

 124., &c. BOSSUT, Hydrodyn. vol. i. 76., 

 &c. 



Steam Engine. 



355. Let a cylinder ABCD (fig. 26.), placed 

 vertically, have a piston working in it, the rod of 

 which is fixed to the end of a beam GH, turning 

 on the axis O, and loaded at its other extremity by 

 a weight W, and when the machine is at rest, let 

 the beam incline toward the side where the weight 

 is. Then if a vacuum be any how made in the 

 part of the cylinder under the piston, the whole 

 pressure of the atmosphere will tend to depress the 

 piston, and will raise the weight W, if its mo- 

 mentum 



