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examined the lubftancc in the glafs, I could not perceive any 

 nioillure. 



The piece of this fubftance which I had left remaining I put into 

 a glafs tube, the cavity of which was not larger than the tip of a 

 child's little finger, whereas the former tube was more than three 

 times that lize. This I examined by the microfcopc, placing the 

 particle in a fomewhat oblique point of view, and then, not with- 

 out wonder, I perceived the globules expelled from it ; which, to 

 the naked eye, appeared as fmoke, not rifmg up on all fides, as is 

 iiniverfally obferved in common fmoke, but, on the contrary, that 

 they tended downwards. 



To illurtrate this, let A B C D, Plate XVIII. fg, \, reprefent tliis 

 piece or particle of fubllance, which is called natural light, and let 

 A be fuppofed the lower and C the upper fide of it, and in this po- 

 fition the globules, expelled between £ D and G, were driven down- 

 wards, that is, towards H, and, in like manner, the globules be- 

 tween E B and F were driven towards 11 ; and \\'hen I made B 

 the lower part, all the expelled matter took its courfe towards K, 

 and if D was made the lower part, then it all tended towards I, 

 This expulfion of globules lalled only two or three days, and, as I 

 faw no farther alteration for the fpace of two or three weeks, I laid 

 the glafles afide. 



This fubllance was fent to me on the fifteenth of April, lOgs, 

 and in the middle of Auguft, in the fame year, I looked at the firrt 

 mentioned glals, when I was greatly furprifed to find that it feemed 

 to be all vaniftied out of the glafs, whence, at firft, I doubted whe- 

 ther this was the real glafs which I had ufed : but, feeing a great 

 quantity of tranfparent moifture in it, I became more fatisfied that 

 it was the same, and the more fo when, upon warming the glafs and 

 the moifture which adhered to it, towards the warmth I faw the 

 moifture immediately change into a white fubllance. I then exa- 

 mined the other, and the fmaller glafs tube, which was still clofed 

 up, and I could not difcern any alteration in the contents. 



