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common air, in a few minutes (by which time the 
effervefcence will be over, and the mixture will have 
recovered its tranfparency) there will want about one 
ninth of the original two meafures. I hardly know 
any experiment that is more adapted to amaze and 
furprize than this is, which exhibits a quantity of 
air, which, as it were, devours a quantity of another 
kind of air half as large as itfelf, and yet is fo far from 
gaining any addition to its bulk, that it is diminished 
by it. If, after this full faturation of common air with 
nitrous air, more nitrous air be put to it, it makes an 
addition equal to its own bulk, without producing 
the leaf! rednefs, or any other vifible efled. 
That this diminution is chiefly in the quantity of 
common air, is evident from this obfervation, that if 
the fmalleft quantity of common air be put to any 
larger quantity of nitrous air, though the two toge- 
ther will not occupy fo much fpace as they did fepa- 
rately, yet the quantity will be Hill larger than that 
of the nitrous air only. One ounce meafure of com- 
mon air being put to near twenty ounce meafures of 
nitrous air, made an addition to it of about half an 
ounce meafure. This, however, being a much greater 
proportion than the diminution of common air, in the 
former experiment, feems to prove that part of the 
diminution in the former cafe is in the nitrous air. 
Befides, it will prefently appear, that nitrous air is 
fubjed to a molt remarkable diminution ; and as 
common air, in a variety of other cafes, fuffers a di- 
minution from one fifth to one fourth, I conclude, 
that in this cafe alfo it does not exceed that propor- 
tion, and therefore that the remainder of the dimi- 
nution refpeds the nitrous air. 
In 
