Obfervations on inflammable Air. 343 
breathed the inflammable air with a kind of fear; but 
finding that it occafioned no painful impreflion, I conti- 
nued breathing it with courage as long as I could, I 
breathed in a bladder filled with it eleven times, be- 
ginning after a natural expiration. This air when 
taken out of the bladder, was if ill inflammable, and 
being tried with the tell of nitrous air it gave II- 28, 
III + 20. 
Befoi'e I go farther I muft explain the formula which 
I ufe to exprefs the diminution of refpirable air, or air of 
other kind, when mixed with nitrous air. My method is 
as follows : I have a glafs tube of about eighteen inches 
in length, and half an inch in diameter, clofed at one 
end, and of a conftant diameter throughout its whole 
length: this tube has a mark at every three inches, 
which marks or divifions I call meafures , and every inch 
is divided into twenty equal parts ; fo that every meafure 
is divided into fixty portions, which I call parts. Into 
this tube, by means of an inftrument which meafures 
always one conftant quantity of air equal to one meafure 
of the tube, I introduce two meafures of refpirable air 
and one meafure of nitrous air, after which I meafure 
the diminution; then I introduce a fecond meafure of 
nitrous air, and again meafure the diminution. The 
whole meafures I exprefs in Roman characters, and the 
Z z 2 parts 
