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The invention of an Eudiometer^ 

 or of an inurnment or contrivance, 

 by v/hich the degree of purity 

 of the common air, or its fit- 

 nefs for refpiration, or rather its 

 wholefomenefs, can be inveftigated 

 juft as well as its weight, and its de- 

 gree of heat and cold, is perhaps 

 one of the more, extraordinary in- 

 ventions which ever was made. 



We owe this important difcovery 

 to the Rev. Dr. Prieilley. He found 

 that nitrous air has the lingular pro- 

 perty of diminiihing, or of being 

 diminifned by, common air in pro- 

 portion to its goodnefs ; or that the 

 bulk of the two airs joined together 

 contracts itfelf in a fo much the 

 narrower fpaee, as the common air 

 is better, purer, or more fit for re- 

 fpiration. It will foon appear to 

 what a considerable degree of accu-? 



racy 



