162 BOOK OF NATURE LAID OPEN, 



ing and evening are made to rejoice, and the long 

 and dismal nights of the polar regions stript of their 

 horrors, the optic nerves would have been overpow- 

 ered by the sun rising in all its glory, and the mo- 

 ment he sunk beneath the horizon, the bewildered 

 traveller left to grope in the dark. 



Although the air cannot be frozen, or perceived 

 by the eye, for the wise reasons already noticed, yet 

 it is capable of being condensed and rarified to an 

 astonishing degree: so much so, that the air in a 

 house may be compressed so as to be made to enter 

 a cavity not larger than the eye of a needle, and the 

 contents of a nut-shell so expanded as to fill a sphere 

 of unknown dimensions. If an empty bladder, with 

 its neck tied close, is laid before the fire, the heat will 

 so rarify the small quantity of inclosed air, as to make 

 it extend the bladder to its full dimensions, and if not 

 then timously removed, will at last break it with 

 the report of a gun. Sir Isaac Newton thinks the 

 air capable of diffusing itself into above a million of 

 times more space than it before possessed. By these 

 remarkable properties of the air, together with its 

 weight and elasticity, it is admirably fitted for some 

 of its most essential uses, and, perhaps, none more 

 so than for the business of animal respiration; for, in 

 this act, so necessary for the prolongation of life, the 

 air, by its weight and condensing power, is forced 

 and compressed into the lungs, while, by its elastic 

 and expanding property, it is thrown out again in 

 the act of breathing. 



