578 MR EDMUND J. MILLS’S 
Movement of the Zero with Temperature. 
It has long been known that the immersion of a thermometer into boiling 
water almost invariably lowers the zero. The only consecutive series of obser- 
vations of the effect of temperature that I have been able to find is due to 
Henrici.* His results are readily comprised in the equation 
y=2'100(981)* — 099(1°360)", 
y being the total remaining ascent, and the unit of 2 being 10°C. The starting- 
point of the observations was 50° C.; and depressions were consecutively 
observed at every 10° to 100°. 
TABLE VII. 
Le Zero Observed. Yy. y Cale. 
0 0:00 2:00 -- 
ap —0:10 1:90 1:92 
3 — 0:25 1°75 1°73 
4 — 0:40 1-60 161 
5 — 0:60 1°40 1°45 
Probable error of a single comparison, : 023 
The depression at 100° in HeEnrict’s instrument is by far the largest at present 
recorded. It can easily be shown from the equation that y=0 when w=9°35 ; 
so that the zero in this case would have begun to rise after immersion of the 
bulb in a bath at 143°'5. 
The following numbers were obtained with thermometers 455, 3 and ¢, all 
of which had cylindrical bulbs. The results for thermometer 3 are given in 
terms of its scale, one division of which was equal to 0°:280. The equations 
are— 
Y4en= 2'869( “998 )*? —-143(1:324)? , 
Ys =4'723(1:006 )*—:723(1:1964)’ , 
Ye =1:112( ‘9986)*—-112(1:299)° . 
The values of a unit of x being respectively 13°, 20°, and 38”. 
* Pogg. Ann. |, 251. 
