256 OUTLINES OF NATURAL PHILOSOPHY. 



PNEUMATICS. 



#46. JL HE doctrine of Pneumatics, treats of 

 elastic fluids, as accelerating or retarding the mo- 

 tion of bodies ; of air, as the vehicle of sound ; and, 

 lastly, of air, as the vehicle by which heat and 

 moisture are distributed over the surface of the 

 earth. It is, therefore, naturally divided into three 

 sections, 



SECT. I. 



AIR AS ACCELERATING OR RETARDING MOTION. 



Machines for raising Water. 



347. J.F a bent tube, open at both ends, have 

 the end of the shorter leg immersed in water ; and 



if 



