t: g@ee a 
715 which being alfo let up in 
the large tube, I begin to fhake 
forcibly this tube in the» water- 
trough exactly 30 feconds (begin- 
ning the motion precifely at the 
moment the two airs come into 
contact), and place it directly after- 
wards in the brafs tube, and let it 
{tand thus in the middle of the 
Gavel mi the fpace of one ae; 
to brig the temperature of the 
glafs tube to that of the water; for, 
- holding it in the hand while fhak- 
ing, it receives fome degree of heat - 
from the hand, and of courfe the co- 
lumn of air within is rarified. I then 
flide the glafs tube up or down 
_. within the brafs tube, which is filled 
with water, till the two columns of 
‘water come to a level with each 
a ener, and with the o of the brafs 
——— ee 8 meafure, 
