Experiments upon Heat . 299 
other. The inftrument, thus prepared, being put under the 
receiver of an air-pump, the air palled freely out of the globe 
and cylinder upon working the machine, but the valve above 
defcribed prevented its return upon letting air into the receiver. 
The gage of the air-pump (bowed the degree of rarity of the 
air under the receiver, and confequently of that filling the 
globe and cylinder, and immediately furrounding the thermo- 
meter. 
With this Inftrument, the weather being clear and fine, 
the mercury in the barometer (landing at 27 inches 9 lines, the 
thermometer at 1 5 0 , and the hygrometer at 47 0 , 1 made the fol- 
lowing experiments. 
(Exp. N° 20.) 
’Thermometer N° 4. 
Surrounded by common 
air, barometer {landing at 
27 inches 9 lines. 
Taken out of freezing wa- 
ter , and plunged into boiling 
water . 
(Exp. N° 2i.) 
Thermometer N° 4. 
Surrounded by air rare- 
fied by pumping till the 
barometer-gage flood at 
6 inches 1 1| lines. 
Taken out of freezing wa- 
ter , and plunged into boiling 
water . 
(Exp. N° 22.) 
Thermometer N a 4. 
Surrounded by air rare- 
fied by pumping till the 
barometer-gage flood at 
l inch 2 lines. 
Taken out of freezing wa- 
ter , and plunged into boiling 
water . 
Time 
Heat 
Time 
Heat 
Time 
Heat 
elapfed. 
acquired. 
elapfed. 
acquired. 
elapfed, acquired. 
— — . 
o° 
— 
0° 
— — 
o° 
M. S. 
0 
M. S. 
0 
M. S. 
© 
O 31 
10 
0 3 1 
10 
0 29 
10 
O 40 
20 
0 38 
20 
0 36 
20 
0 41 
30 
0 44 
30 
0 49 
30 
0 47 
40 
0 51 
40 
1 1 
40 
1 4 
5 ° 
1 7 
50 
1 1 
50 
1 25 
60 
1 19 
60 
1 24 
60 
2 28 
70 
2 27 
70 
2 31 
70 
10 17 
80 
10 21 
80 
not obferved. 
80 
7 36 zztotal time of 
7 37 = 
total time of 
7 ci = total time of 
heating from 0 
0 to 70°. 
heating from o° to 70°. 
heating from O 0 
to 70°. 
R r 2 
The 
