MENTAL AND CORPOREAL. 265 



destroyed when the air is withdrawn from the 

 lungs. But he had not then acquired a know- 

 ledge of the nature and proper ties of ibis substance, 

 or even of its existence, but from the effects pro- 

 duced ; much less the cause of its pressing upon 

 other bodies, which, when not sufficiently re- 

 sisted, put them in motion; thus suggesting 

 the invention of sails for the purposes of naviga- 

 tion, since brought to such perfection, and of 

 windmills, now of the most comprehensive use. 

 It was not be expected that the laws of this 

 invisible agent should be understood during the 

 early experience of mankind, it was conse- 

 quently not until a vast collection of facts had 

 been recorded, and the mind had made great 

 progress in reasoning upon causes, it was finally 

 ascertained, that the atmosphere was as much a 

 substance as any tangible body, possessing elas- 

 ticity, density, gravity, and fluidity ; that it was 

 composed of two or three distinct ingredients 

 chemically combined ; that it held in solution or 

 in combination, various other substances, as the 

 electric fluid, caloric, water, and terrestial exha- 

 lations ; and that it entered into the composition 

 of most other natural bodies ; from all which 

 circumstances, new sciences have emanated, and 

 a variety of the most useful instruments have 

 been invented : which, explaining the causes of 

 the various atmospherical phenomena, have 

 increased human knowledge, and removed 



