520 On Heat € Cold produced by Mechanical 
of the heat lost. Upon opening the cock, the. 
receiver filled with air in five seconds, and the 
greatest volocity of the rising mercury was about 
the end of that time. The rising continued 
for 30 or 40 seconds from its commencement, 
but ¢ of the effect were produced in the first 
10 seconds. The greatest velocity of the rising 
mercury is 1°in 37 seconds. After the thermos 
meter had attained its utmost height, it be- 
gan to fall again at the rate of vo of a degreé 
in a minute, 
EXPERIMENT 6. 
Took the same thermometer and heated it fe 
50° above the temperature of the air, then let 
it be cooled by the medium of air, and it be. 
gan to fall at the rate of 1° in 3 seconds. 
The two last experiments séem to prove’ that 
when air is let in to the receiver in the ordinary 
way, an increase of temperature of 50° 1s produced 
in the medium within the receiver for 3: seconds. 
. This high temperature is reduced in a@ few seconds 
by the receiver and surrounding bodies, to their 
own temperature, 
