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its whole length ; but this only when prefented to the middle, 

 not the ends, this latter firft occurred when the rarefadlion 

 was greater; and then at every approach and recefhon of the 

 excited tube, without frefh excitation, even for fifty times to- 

 gether, and with fcarce any diminution of brightnefs to the 

 laft, or fign of decay until I ceafed to prefent it, fuch flaflies 

 were produced ; they filled the whole tube, but that they were 

 brighter and of fmaller diameter at the middle of its length ; 

 they were alfo not only denfer but of a more yellow colour, than 

 the faint corufcations before defcribed: but the mofl diftindlive 

 difference between both thefe kinds, and indicating the great 

 degree of rarefadlion neceffary for the exhibition of the former 

 was, that when ihsy appeared, the excited tube produced no 

 light at all in the other, except at the firjl prefentation and 

 aEliial contaSi with it : from which I concluded (too flupidly 

 and haftily) that the eledlricity of the former was completely 

 difcharged, and that the more perfetSt vacuum, was a more 

 perfedl condu6lor of elecflricity, even more fo than metals : 

 but though I am yet of opinion that the fadl was fo, yet it 

 may, for ought I know, be polfible, that the tube produced no 

 light after the firft prefentation, not becaufe it was quite dif- 

 charged, but becaufe its eletflricity, ielFened by the firfl d,f- 

 charge, would not pafs nor be conducted by the more perfedl 

 vacuum in the other tube ; or, if it burns, deftroys, or changes 

 into nitrous acid the air which conduits it, what remained 



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