OUTLINES OF NATURAL PHILOSOPHY. 



tained in it, but by the state of movement or vibra- 

 tion in which the caloric exists, (which state per- 

 cussion and friction may very much determine,) this 

 appearance will also admit of a solution. 



SECT. II. 

 EQUILIBRIUM OF ELASTIC FLUIDS. 



336. JL HE fundamental theorems demonstrated 

 in the first section of Hydrostatics, are common to 

 the compressible and the incompressible fluids. 



See articles 247, 248, &c. 



337. As Atmospheric Air is the best known of 

 all elastic fluids, we shall take it for the subject of 

 our investigation, defining it, A heavy and elastic 

 fluid, which resists compression with forces that are 

 directly as its density, or inversely as the spaces 

 within which the same quantity of it is contain- 

 ed. 



The accuracy of this definition is known from expe- 

 rience. 



