472 PROFESSOR W. RAMSAY AND DR. S. YOUNG ON THE INFLUENCE OF 
must therefore register the same temperature. It was found that the two thermo¬ 
meters by Negeetti and Zambra agreed throughout as to the length of their 
divisions; and a curve was constructed, showing the relation of the degrees on 
thermometer B to those of A. 
28. It is worth recording that the zero-points of all the thermometers were lowered 
on reduction of pressure, but to very different amounts. The readings under atmo¬ 
spheric pressure of thermometers A and C, when placed in ice, being taken as identical, 
it was found that in a vacuum thermometer C stood 0 o- 5 lower than A. A similar 
phenomenon has been observed by Mills. After coating thermometers with metals 
electrolytically, he noticed that the deposition of zinc and cadmium lowered the zero- 
points of his thermometers from 0'27 to 0’75 degree, while copper raised the zero-point 
in one case as much as 14’70 degrees (Proc. Boy. Soc., vol. 26, p. 504). Mills made a 
comparison of this effect with that produced by raising or lowering atmospheric pressure. 
The following table shows a comparison of thermometers A and B, by the method 
already mentioned :— 
Number of experiments, 
mean of. 
Temperature of A. 
Temperature of B. 
Difference. 
O 
O 
O 
4 
-2-82 
— 3 16 
0-34 
1 
372 
4T0 
0-38 
3 
4 - 66 
-5-06 
0-40 
2 
5-06 
5-53 
0-47 
2 
+ 0-10 
0-21 
0-31 
2 
0Y5 
0T7 
0-32 
2 
-2 33 
2-68 
0-34 
1 
362 
4-04 
0-42 
1 
1-80 
2-18 
0-38 
1 
2*92 
3-34 
0-42 
1 
3-87 
4-30 
0-43 
4 
4-59 
5-09 
0-50 
3 
4-35 
4-77 
0-42 
2 
4-93 
5-38 
0-45 
1 
0-66 
TOO 
0-34 
The extreme variation in difference amounted to 0°T9. The difference was found 
to increase with fair regularity as the temperature fell. 
30. From these numbers the following table was constructed by the graphic 
method:—Zero-points of A and B under the same conditions were respectively 
-|-0 o Tl and —0°'21. A and C (of which the zero-point had been raised to 7°'23 for 
convenience of reading) were found to be identical throughout, hence then’ readings 
were accepted as correct, while those of B were corrected as given in the table 
below :— 
