41 8 On the Conjlituenl Parts 



fluid perfectly fimilar to that of the atmofphere, and which 

 has all its properties. 



The following, on the other hand, are the corollaries 

 which I have deduced from a great number of experiments 

 made to afcertain the duration of animal life in noxious 

 aeriform fluids, mixed in different proportions with oxygen 

 gas, tending to illuftratc the real compofition of atmofpheric 

 air. 



1. The examination by means of burning tapers is not 

 accurate for afcertaining the falubrity of the air. I (hall 

 quote only two examples. A fifth part of oxygen gas 

 mixed with air contaminated by the vapour of fulphur, 

 fuffered a candle to burn, while an animal (hut up in it 

 died in a few feconds. A feventh part of the fame gas 

 mixed with air vitiated by the vapour of charcoal, fupported 

 flame, while an animal died in it almoft inftantaneoufly. 



2. That pure and falutary part faid to be contained in at- 

 mofpheric air, which forms a third of it according to 

 Scheele, and a fourth according to Lavoifier, is not a real 

 dephlogifticated oxygen gas ; fince this gas united with 

 mephitic airs, in a much lefs proportion than a third or 

 fourth, fupports the flame of a candle after an animal dies 

 in it, which is not the cafe with atmofpheric air. 



3. The real component parts of atmofpheric air are Mill 

 Unknown; fince, with a mixture of different gafes, no- 

 thing has been obtained but compound gafes, which have 

 indeed fome properties of air, but never thofe of atmo- 

 fpheric air. 



The author, to illuftrate the queftion, relates eight cha- 

 racierifing marks of atmofpheric air, acknowledged by phi- 

 lofophers ; and adds, that though he tried, by a multitude 

 of experiments, to compofe atmofpheric air, by mixing de- 

 phlogifticated gas with different mephitic gafes, the gafes 

 fo obtained always contained fomething not to be found 

 in atmofpheric air. 



He 



