TrfE EARTH. 285 



up strong fires, take proper precautions to ex- 

 clude the beams of the sun from shining upon 

 them, which effectually puts them out. This 

 they are apt to ascribe to a wrong cause, namely, 

 the operation of the light ; but the real fact is, 

 that the warmth of the sun-beams lessens and 

 dissipates the body of the air that goes to feed 

 the flame ; and the fire, of consequence, languishes 

 for want of a necessary supply. 



The air, while it thus kindles fire into flame, is 

 notwithstanding found to moderate the rays of 

 light, to dissipate their violence, and to spread 

 an uniform lustre over every object. Were the 

 beams of the sun to dart directly upon us, with- 

 out passing through this protecting medium, they 

 would either burn us up at once, or blind us with 

 their effulgence. But by going through the air, 

 they are reflected, refracted, and turned from 

 their direct course, a thousand different ways ; 

 and thus are more evenly diffused over the face 

 of nature. 



Among the other necessary benefits the air is 

 of to us, one of the principal is its conveyance of 

 sound. Even the vibrations of a bell, which have 

 the loudest effect that we know of, cease to be 

 heard when under the receiver of an air-pump. 

 Thus all the pleasures we receive from conversa- 

 tion with each other, or from music, depend en- 

 tirely upon the air. 



Odours likewise are diffused only by the means 

 of air ; without this fluid to swim in, they would 

 for ever remain torpid in their respective sub- 

 stances j and the rose would affect us with as 



