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nitrons air in this method is, that 

 more meafures of it are required 

 before the faturation of the air to 

 be examined is compleated. 



The reafon of this will appear 

 obvious, if we confider that it is 

 only the true nitrous air which is 

 capable of diminifhing refpirable 

 airs, and that it performs this dimi- 

 nution in the proportion to its 

 Itrength, fo that weak nitrous air 

 will always diminifh common air 

 in the proportion of its own good 

 or bad quality. Now I will fup- 

 pofe that the nitrous air, to be added 

 to the two meafures of common air, 

 is become fo weak, either by Hand- 

 ing, or by the admiflion of any 

 other air, as to pofTefs only half the 

 ftrength of good nitrous air. The 

 confequence will be, that as much 

 again cf it will be required to fa- 



turate 



