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the I'mall veflels, and thereby produce red fpots on the Ikin ; and I 

 have often thought whether foniething like this might not be the 

 caule of thofe fmall ulcers on the ikin, which we lee in the fmallr 

 pox. But thefe are only my own private fpecxilations, which I fub- 

 mit to the judgment of thofe who make thefe matters their tludy. 



In farther profecution of thefe experiments, I took rainwater well 

 boiled, and after it was cooled, I put it into a clean glafs, firfl wash- 

 ing out the glafs with the fame water, and let it Hand in my Itudy un- 

 covered for two days. On the third day, I placed the glafs in the 

 window, w'hich fronted the North-eaft, where it remained all day, 

 the fun lliining bright with a cold wind from the North. The fol- 

 lowing day I took my largeft glafs inllrument, which I rinfed out 

 with fomeof this water, and then filled it with more of the fame 

 water, then doling the end of the fmall tube, and applying my 

 operation of pumping, I faw air bubbles rife out of this water in 

 greater quantity than I had feen in rain water not boiled, but taken 

 out of the cillern. Having drawn out the pillon, I faw that when 

 the fubtle air had efcaped, a greater quantity of common air re- 

 mained in the fmall tube than I had before feen in the water which 

 was not boiled, and according to my computation, the quantity of 

 air produced was a two hundredth part of the bulk of the water. 



I requefted a furgeon of my acquaintance, that when he Ihould 

 bleed any perfon, he would fend me fome of the blood ; in confe- 

 quence of which, I received from him a velTel with fome blood 

 which had been about half a quarter of an hour expofed to the air 

 before I received it. This blood was fo thick, that in two eflays 

 to fill the glafs tube with it, the air found its way into the tube, 

 and it was not till the third trial that I could fill the tube with 

 blood only ; by which means I apprehend that more air was intro- 

 duced into the blood, than if I could at once have put it into the 

 tube. Upon applying the operation of extrading the air, I faw 

 large air bubbles ariie out of the blood ; but upon taking out the 

 pifton, I found, according to the mofl: accurate computation I 



