440 
.AJR. GEORC4E W. AVALKER OX THE DEPENDENCE OF THE 
5 millims. apart in tlie eye-piece, and the breadth of a band about 1 millim., or bth of 
the distance between t^^o bands. It is therefore useless to have a screw micrometer 
reading to x'ootli of band wlien the eye cannot judge more than -ixyth. In the case 
of air at 10 C., 100 bands corresponds to a difference in level in the limbs of the 
manometer of about 16 centims. We may therefore consider the quantitv 
pressure 
to lie accurate to 1 part in 500. 
Wit!) regaid to tlie thermometers, the}^ weie made hy It. Mittelbach, in Got¬ 
tingen, and divided in half degrees from 0° C. to 100° C. They could easily be read to 
-nyth of a degree, but this accuracy is not necessary. I had one of the thermometers 
standai dised at Kew and compared the others with it under the same conditions as 
in the experiments. The thermometers used in the experiments were placed in a 
bath at constant temperature, the same amount of stem being exposed as in the 
actual experiments, while the standardised thermometer was completely immersed. 
Atmospheric Air. 
The air in the laboratory was used, and dried by means of phosphoric pentoxide. 
The tap L was kept shut so that the same air was in the apparatus throughout the 
exjieriments. 
It would serve little purpose to give all the readings taken; and I shall confine 
myself to a few specimens. Throughout the initial pressure was as nearl)- as possible 
atmospheric j^ressure. 
The thermometers in the jacket were marked 7 and 9, and the thermometer placed 
under tlie scale of the manometer jnarked 6. 
15th November, 1901. 
Readings of thermometers 
in degrees Centigrade. 
Readings 
of manometer in 
centimetres. 
Number 
of 
bands. 
Differences. 
Ratio, 
bands 
pressure' 
9 
7 
6 
Right 
limh. 
Left 
limb. 
Pressure. 
Bands. 
10-3 
10 
13-4 
15-60 
15-60 
(1) . . 
10-3 
10 
13-5 
23-49 
7-58 
100 
15-91 
100 
6-285 
(2) . . 
10-2 
9-9 
13-5 
15-65 
15-57 
99-4 
15-83 
99-4 
6-279 
10-2 
9-9 
13-5 
15-60 
15-60 
_ 
- 
_ 
(3) . . 
10-3 
10 
13-5 
23-48 
7-58 
100 
15-90 
100 
6-289 1 
(4) . . 
10-4 
10-1 
13-5 
15-60 
15-60 
99-8 
15-90 
99-8 
6-276 
10-4 
10-1 
13-5 
15-60 
15-60 
_ 
(5) . . 
10-4 
10-1 
13-7 
21-88 
9-2 
79-6 
12-68 
79-6 
6-277 
(G) . . 
_ 
10-4 
10-1 
13-7 
15-81 
15-37 
76-6 
12-24 
76-6 
6-258 
The correction for each of the thermometers at this temperature was -|- ’4° C, 
