Atmosphere. 91 



plilogisticated, is in reality a compound, 

 and might be artificially produced in va- 

 rious ways. This dephlogisticated air,> 

 however, is but a small part of the com- 

 position of our atmosphere. By accu- 

 rate experiments, the air we usually 

 breathe, is composed of only one-fourth 

 part of this dephlogisticated air, or per- 

 haps less, the other three parts, or more, 

 consisting of what Dr. Priestly calls phlo~ 

 gisticated, and M. Lavoisier, in the new 

 chemistry, mephitzc, or azotic air, which 

 cannot be breathed, and in which ani- 

 mals die. 



Though air seems to be a kind of re- 

 pository, wherein all the poisonous efflu- 

 via arising from putrid and corrupted mat- 

 ters are lodged ; yet it has a wonderful 

 facilitv of purifying itself, and of deposi- 

 ting those vapours contained in it ; so 

 that it never becomes noxious except in 

 particular places, arid for a short time ; 

 the general mass remaining upon all oc- 

 casions pretty much the same. The way 

 in which this purifaction is effected is dif- 

 ferent, according to the nature of the va- 

 pour with which the air is loaded. That 

 which most universally prevails is water ; 



