r res J 
The invention of an Eudiomeier, 
or of an initrument or contrivance, 
by which the degree of purity 
of the common air, or its--fit- 
nefs for refpiration, or rather its 
wholefomenefs, can be inveitigated 
juttas well as its weight, and its de- 
mus? 18 of, supa and cold, is perhaps 
3 ser owe this important difcovery 
to the Rev. Dr. Prieitley. He found 
that nitrous air has the fingular-pro- 
perty of diminifhing, or of being 
diminifhed -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 fpace, as the common air 
is better, purer, or more fit for re- 
fpiration. It will.foon appear to 
what a confiderable eae of ; 
