40 
DRS. W. RAMSAY AND S. YOUNG ON THE INFLUENCE OP 
6. The first series of readings gave the following results :— 
Number of 
readings. 
Mean temperature 
of condenser. 
Mean temperature 
of bulb. 
Difference. 
Difference 
calculated. 
O 
Q 
O 
O 
7 
-11-1 
-8 
3-1 
3-2 
1 
- 9-2 
-6-4 
2-8 
2-8 
4 
- 8-05 
-5-6 
2-45 
2-5 
4 
- 5-5 
-3-3 
2-2 
2-3 
6 
- 3-2 
-1-3 
1-9 
1-9 
The second series gave similar numbers :— 
Number of 
readings. 
Mean temperature 
of condenser. 
Mean temperature 
of bulb. 
Difference. 
Difference 
calculated. 
O 
O 
O 
4 
— 17-7 
-9-35 
8-35 
8-35 
1 
-16-7 
-8-9 
7-8 
7-9 
3 
-15-5 
-8-3 
7-2 
7 - 4 
4 
-14-5 
-7-6 
6-9 
6-9 
3 
-13-6 
-6-8 
6-8 
6-5 
1 
-12-7 
-6-3 
6-4 
6'2 
At this point the bulb of the thermometer became slightly exposed, and it is seen 
that the temperature shown by this thermometer rises more rapidly :— 
Number of 
readings. 
Mean temperature 
of condenser. 
Mean temperature 
of bulb. 
Difference. 
Difference 
calculated. 
O 
O 
O 
2 
-11-45 
-5-45 
6-0 
5-7 
3 
-10-6 
-4-5 
6-1 
5-4 
9 
- 9-0 
-3-2 
5-8 
4-9 
10 
- 7-3 
-1-5 
5-8 
4-4 
It is to be observed that in each case the thermometer in the ice-bulb shows a 
higher temperature than that in the condenser, and that as the temperature rises the 
difference decreases. 
7. The question arises :—On what does this difference depend ? The answer which 
naturally occurred to us was that the temperature of the ice depends on the pressure 
in the apparatus, which in its turn depends on the temperature of the condenser. 
Assuming the truth of this hypothesis, it was possible to calculate the pressure 
exerted by the air in the apparatus for any one temperature in the following way :— 
In the first series of experiments the tension, ascertained by Regnault’s tables, cor¬ 
responding to the temperature —3 0, 2 in the condenser, is 3'59 millims.; that corre» 
sponding to the temperature —1 0, 3 of the ice is 4T6 millims. Assuming the tempera¬ 
ture of the ice wholly to depend on the pressure in the apparatus, the pressure would 
