[ 6 4 i ] 
fully marked. I then raifed the Mercury, by heat, 
to the top of the tube, and fealed the tube hermeti- 
cally ; and when the mercury was brought to the 
fame degree of heat as before, it flood in the tube ~ 0 <r 
of an inch higher than the mark. 
The fame ball, and part of the tube being filled 
with water exhaufted of air, inflead of the mercury ; 
and the place where the Water flood in the tube 
when it came to reft in the heat of 5° degrees, being 
marked, which was about 6 inches above the ball; 
the water was then raifed by heat till it filed me 
tube; which being fealed again, and the watei 
brought to the heat of 50 degrees as before, it flood 
in the tube °f an * nc h a ^ ove mar ^* 
Now the weight of the atmolphere for about 73 
pounds avoirdupois) prefling on the outnde of the bait 
and not on the infide, will iqueeze it into lefs 00m- 
pafs. * And by this comprefiion of the ball, the 
mercury and the water will be equally raifed in the 
tube : but the water is found, by the experiments 
above related, to rife J-J-o °f an more tlian 
mercury; and therefore the water muff expand, 
fo much, more than the mercury, by removing the 
weight of the atmofphere. 
In order to determine how much water is com- 
prefled by this, or a greater weight, I took a glafs 
ball of about an inch and -% in diameter which was 
joined to a cylindrical tube of 4 inches and -^-g- ut 
length, and in diameter about -M-o of an ' mc ^ > anc * 
* See an account of experiments made with glafs balls by Mr. 
Hooke, (afterwards Dodtor Hooke,) in Dodtor Birchs hiftory 
of the Royal Society, Vol. 1. page 127. 
4 n 2 b y 
