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No kind of air, on which I have yet made the 

 experiment, will conduct electricity ; but the colour 

 of a fpark is remarkably different in fome different 

 kinds of air, which feems to fhew that they are not 

 equally good non-conductors. In fixed air, the 

 electric fpark is exceedingly white ; but in inflam- 

 mable air it is of a purple, or red colour. Now, 

 fince the moft vigorous fparks are always the whiteft, 

 and, in other cafes, when the fpark is red, there is 

 reafon to think that the electric matter paffes with 

 difficulty,, and with. lefs. rapidity : it is poffible that 

 the inflammable air may contain particles which 

 conduct electricity, though very imperfectly; and that 

 the whitenefs of the fpark in the fixed air, may be 

 owing to its meeting with no conducting particles 

 at alL When an. explofion was made in a quantity 

 of inflammable air, it was a little white in the 

 center, but the edges of it were, (till tinged with a 

 beautiful purple. The degree of whitenefs in this 

 cafe was probably owing to the electric matter Turn- 

 ing with more violence in an explofion than in a 

 common fpark. 



Inflammable air kills animals as fuddenly as fixed 

 air, and,, as £ar as can be perceived, in the fame 

 manner, throwing them into convulfions, and there- 

 by occasioning prefent death. I had imagined that, 

 by animals dying in a quantity of inflammable air, 

 it would in time become lefs noxious; but this did 

 not appear to be the cafe y for I killed a great number 

 of mice in a fmall quantity of this air, which I kept 

 feveral months for this purpofe, without its being at 

 all fenfibly mended j the laft, as well as the firft 

 moufe a dying the moment it was. put into it. 



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