1 2I + 3 
; by nitrous air, I inclofed a veflel full of lime wa- 
’ter in the jar in which the procefs was made, hut 
it occafioned no precipitation of the lime; and 
'when the veflel was taken out, after it had been 
jin that fituation a whole day, the lime was eafily 
precipitated by breathing into it as ufual. 
It is exceedingly remarkable that this efiervefcencc 
• and diminution, occafioned by the mixture of ni- 
trous air, is peculiar to common air, or air fit for 
•'refpi ration ; and, as far as I can judge, from a 
great number of obfervations, is at lead very 
nearly, if not exactly, in proportion to its fitnefs 
for this purpofe; fo that by this means the good- 
nefs of air may be diflinguiflied much more accu- 
rately than it can be done by putting mice, or any 
'Other animals, to breathe in it. This was a mod 
agreeable difcovery to me, as I hope it may be an 
-uieful one to the public; efpecially as, from this 
time, I had no occafion for fo large a dock of mice 
as I had been ufed to keep for the purpofe of thefe 
experiments, ufing them only in thofe which re-'' 
quired to be very decifive ; and in thefe cafes I have 
.leldom failed to know beforehand in what manner 
■they would be affedted. 
It is alfo remarkable that, on whatever account 
air is unfit for refpiration, this fame ted is equally 
applicable. Thus there is not the lead efferve- 
scence between nitrous and fixed air, or inflamma- 
ble air, or any fpecies of diminifhed air. Alfo the 
•degree of diminution being from nothing at all to 
more than one third of the whole of any quantity 
<of air, we are by this means in pofieflion of a pro- 
.digioudy large fcale, by which we may didinguifh 
j very 
