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tants of the earth, but of the waters too. Without it 

 most animals live scarce half a minute, and none of them 

 many days. 



And not only animals, but even trees and plants owe 

 their life and vegetation to this useful element : as is 

 manifest irons their glory and verdure in. a free air, and 

 their paleness and sickliness, when excluded from it. 



Thus necessary is the air to the life of animals, and 

 it is no lesjs so, to the conveyance of many of theme 

 All the winged tribes owe their flight and buoyancy to it. 

 And even the inhabitants .of the waters cannot easily- 

 ascend or descend in their own element without it. 



It would be endless to specify theaises of the air in/ 

 the operations of nature. To touch only on one or two 

 instances. How admirable is that property of it, the 

 conserving animated bodies, whether animal or vegeta- 

 ble, while it dissolves all other bodies ; by which means 

 many things which would prove nuisances to the world, 

 are put out of the way, and reduced to -their first princi- 

 ples. Even crystal glasses, especially if not used, it will > 

 in time reduce to powder. And thus divers minerals, , 

 stones, fossil-shells, trees, which have lain under ground 

 for many ages, and so secure from corruption, when ill 

 the open air, have quickly mouldered away. 



Another admirable use of the atmosphere is* its minis- 

 tring to the enlightening the earth, by reflecting to us the* 

 light of the sun, * and refracting his beair-s -to our eye, 

 berbre he surmounts our horizon, by which means the, 



only, but the too great lightness thereof, which renders it unable 

 to be a counter-balance to the heart, and all the muscles minister* 

 ing to the respiration. 



* To tnis is owing that whiteness which is in the air in the day 

 time, caused by the rays of light, striking on the particles of the at- 

 mosphere, as well as upon the clouds above, and the other objects 

 beneath on the eajth. To the same cause we owe the twilight, 

 namely, to the sun-beams touching the uppermost parts of the at- 

 mosphere, which they do, when the sun is eighteen degrees below 

 the horizon. 



