8o Literary and Philosophical Society, 



standing, at the same time that it affords him the most 

 rational amusement ; whilst the study of some, in particu- 

 lar, may not only tend to effect these desirable purposes, 

 but supply him with a kind of information which may turn 

 to good account, by furnishing him with the means of 

 extending his commercial concerns, and conducting them 

 to greater advantage ; of improving those manufactures in 

 which he is already engaged, or inventing new fabrics, which 

 may give additional life and spirit to trade. 



* As Pneumatics, or the doctrine of the nature and 

 properties of air, display an ample field of investigation to 

 the philosopher, so will they also supply to the more 

 superficial inquirer much instruction and entertainment. 

 Every man is interested in the properties of a fluid to 

 which he is so intimately related, and without which he 

 cannot subsist a moment. Its various degrees of gravity, 

 elasticity, heat, moisture, and purity, all affect the human 

 race. Many of the most dire diseases which affect mankind 

 are occasioned by noxious impregnations of the atmosphere, 

 or cured by more favourable states of it. And many of 

 the operations of nature and art are essentially influenced 

 by the changes which are continually occurring in it. 



* Philosophy has lately made most rapid advances in 

 discovering the constitution of common air. The ingenious 

 Dr. Priestley has even taught us the art of fabricating it 

 artificially, of producing it in a degree of purity far exceed- 

 ing that of the most salubrious climate, and of reducing it 

 to the state in which we commonly breathe it when debased 

 by exhalations from the various bodies which it surrounds. 

 From him we have also learned a mode of judging of the 

 different degrees of purity in air, by means of the eudio- 

 meter, as of its gravity and heat by the barometer and 



