290 PRESSURE IN THE AIR, 



cant space which is made by the passage of 

 moving bodies through the air, becomes imme- 

 diately filled ; and, finally, that the unresisting 

 medium which is produced in the cavity of 

 the thorax, in the class of mammalia, by the 

 elevation of the ribs, and depression of the 

 diaphragm ; enables the expansible power of 

 the air to enter the mouth and nostrils, to 

 fill and distend the bronchia of the lungs, and 

 to accomplish the process of inspiration to 

 accomplish it, with as much perfection in those 

 animals which descend from the upper regions 

 of the air, as it does in those that ascend up to. 

 them ; in an ass, whose mouth is pinned 

 down to the surface of the earth, as it is in a 

 whale, which receives the air from the upper 

 surface of the water. 



Although we possess no means of obtaining 

 atmospherical air, at the highest points of ele- 

 vation, in a state of the utmost dilatation, we> 

 nevertheless, can imitate by art the same state 

 of rarefaction, near the surface of the earth, as 

 the air, probably, undergoes in the upper re- 

 gions of the firmament. However varied the 

 means may be, the object is the same ; 

 whether .that rarefaction be accomplished 

 by an exhausting syringe, according to Mr. 

 BOYLE'S plan, whether by filling a tube with 

 mercury, as TORHICKLLI did ; or by the aid of 



