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importance to mankind ; I refer vet! 

 this article for the laft, not. difcon- 

 tinuing to purfue my experimental 

 enquiries till the book was already 

 nearly printed off. Befides, it was 

 but in the middle of September 

 that I got the brafs tube, exprefTed 

 in Fig. I. in which the glafs tube 

 or great meafure is fufpended ; fo 

 that the column of water within and 

 without the glafs tube be at a per- 

 fect leve! 9 which is necefTary to 

 obtain a refult conftantly the fame 

 with the fame air. This brafs tube 

 is a valuable addition to the appa- 

 ratus. 



I had before that time made ex- 

 periments every day with the atmo- 

 fpheric air, placing the glafs tube 

 in a cylindrical jar filled with water, 

 and lifting up the glafs tube till 

 the extremity of the column of 

 T 3 water 



