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The method of Abbe Fontana in 

 putting the different fpecies of air 

 to the nitrous tefl, cut fhort to the 

 whole difficulty arifing from the 

 inconftancy of ftrength in the ni- 

 trous air. By over-faturating the air 

 to be examined with nitrous air, it 

 imports little what ftrength nitrous 

 air has, though even it had loft al- 

 moit its whole power of abforbing 

 common air. 



In the method adopted by other 

 philofophers, by which always a 

 certain proportion of nitrous air 

 is added at once to a certain quan- 

 tity of the air under -examination, 

 the remit is very uncertain if the 

 nitrous air be not exactly always of 

 the fame quality. But in the me- 

 thod of Abbe Fontana this article is 

 of no confequence at all,. The 

 only difference arifing from weak 



nitrous 



