I 21 '4 ] 



] hv nitrous, air, I inclofed a vefiei full of lime wa- 



ter in the jar in- which the procefe was made, but 



it occafioned no precipitation of tTie lime; and 



when the veifel was taken out, after it had been 



iln that fituation a whole day, the lime was eafiljr 



: precipitated by breathing into it as ufual. 



It is exceedingly remarkable that this efTervefcence 

 : and diminution, occafioned by the mixture of ni- 

 -trous am, is peculiar to common air, or air fit for 

 urelpi ration; and, as far as I can judge, from a 

 great number of obfervations, is at leaft very 

 nearly, if not exactly, in proportion to its fitneis 

 for this purpofe; fo that by this means the good- 

 nefs of air may be diftinguifhed much more accu- 

 ratelythan 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 flock 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 theie cafes I have 

 Seldom failed to know beforehand in what manner 

 .they would be affected. 



It is alfo remarkable that, on whatever account. 

 air is unfit for refpiration, this fame ted is equally 

 .applicable. Thus there is not the leaft efrerve- 

 fcence 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 

 imore than one third of the whole of any quantity 

 ;of air, we are by tins means in pofieftion of a pro- 

 idigiouily Large icale, by which we may diftinguifh 

 j very 



