THE EARTH. 255 



CHAPTER XVIII. 



A NUMMARY ACCOUNT OF, THE MECHANICAL 

 PROPERTIES OF AIR. 



HAVING described the earth and the sea, we now 

 ascend into that fluid which surrounds them both, 

 and which, in some measure, supports and sup- 

 plies all animated nature. As, upon viewing the 

 bottom of the ocean from its surface, we see an 

 infinity of animals moving therein, and seeking 

 food, so, were some superior being to regard the 

 earth at a proper distance, he might consider us 

 in the same light ; he might, from his superior 

 station, behold a number of busy little beings, 

 immersed in the aerial fluid that every-where 

 surrounds them, and sedulously employed in pro- 

 curing the means of subsistence. This fluid, 

 though too fine for the gross perception of its in- 

 habitants, might, to his nicer organs of sight, be 

 very visible ; and while he at once saw into its 

 operations, he might smile at the varieties of 

 human conjecture concerning it : he might rea- 

 dily discern, perhaps, the height above the sur- 

 face of the earth to which this fluid atmosphere 

 reaches : he might exactly determine the pecu- 

 liar form of its parts which gives it the spring or 

 elasticity with which it is endued : he might dis- 

 tinguish which of its parts were pure incorrupti- 

 ble air, and which only made for a little time to 

 assume the appearance, so as to be quickly re- 



