[7 
importance to mankind; I referved — 
this article for the laft, not difcon- 
tinuing to purfue my experimental 
enquiries till the book was already 
nearly printed off. Befi des, it was 
‘but in the middle of September 
that I got. the brafs tube, expreffed 
in Fig. I. in which the glafs tube 
or great meafure is fufpended; fo 
chat the column of water within and 
HD the case babe be at a per- 
fe& Jevel,-- aamacell= y -to 
obtain a refute eBfitta ntly the fame 
with the fame air. This brats ‘tube 
is a valuable addition to the appa- 
_ ratus. 
- Thad before that time made ex- 
periments every day with the atmo- 
dpheric air, placing the glafs tube 
in a cylindrical jar filled with water, 
and lifting up the glais tube. till 
tlie extremity of~--the column of 
~ > 3 water 
