COMPARISON OF THERMOMETERS. 
777 
the composition of the glass, and perhaps also upon the manner in which it is 
worked by the glass-blower. Legrand observed depressions of from 0°"3 to 0°’5 in 
thermometers by M. Bunten*. Despretz found changes amounting to 0°'47, 0°’45, 
0°'23, 0°‘30, 0°‘57, 0°'61, 0°'60, 0°’60 ; and that the freezing-point became stationary 
at the end of about four years Mr. Welsh has observed a depression in the 
thermometers constructed at Kew varying from 0°‘09 to 0°'ll. In the thermo- 
meters employed by Mr. Sheepshanks it amounts to about 0°'17. In ten different 
thermometers examined by Dr. Lamont, the depressions were 0°*31, 0°'28, 0°‘45, 
0°‘25, 0°*31, 0°'37, 0°'62, 0°'25, 0°'31, 0°'27 respectively. He also found that it takes 
about five years for the zero to regain its permanent position after boiling 
The depression of the freezing-point of B below +0°T1, from March 1845 up to 
January 1851, is represented with sufficient accuracy by 0‘0044wi^, where m is the 
time in months up to the middle of January 1851. The computed depressions are, — 
1 845. March, April 0*22 
May 0-21 
June, July 0‘20 
August 0*19 
September, October ... 0*18 
November, December.. 0*17 
1846. January, February 0*1 6 
March, April 0*15 
1846. May, June 0*14 
July, August 0*13 
September, October ... 0*12 
November, December . 0*11 
1847. January — March 0*10 
April — June 0*09 
July, August 0*08 
September — November 0*07 
O 
1847. December — February... 0*06 
1848. March — June 0*05 
July — September 0*04 
October — February ... 0*03 
1849. March — July 0*02 
August — February 0*01 
1850. March — December ... 0*00 
Means of Comparisons of B and K in February and March 1855. 
No. of comparisons. 
B. 
K. 
B-K. 
K-A 
B - t . 
10 
4*895 
4*712 
0*183 
0*003 
0*186 
10 
5*344 
5*177 
0*167 
0*003 
0*170 
10 
6*319 
6*143 
0*176 
0*003 
0*179 
10 
9*219 
9*016 
0*203 
0*006 
0*209 
10 
10*740 
10*493 
0*247 
0*006 
0*253 
10 
12*893 
12*652 
0*241 
0*008 
0*249 
10 
14*532 
14*279 
0*253 
0*009 
0*262 
10 
15*336 
15*095 
0*241 
0*009 
0*250 
10 
16*379 
16*126 
0*253 
0*009 
0*262 
10 
17*581 
17*329 
0*252 
0*010 
0*262 
10 
18*000 
17*749 
0*251 
0*010 
0*261 
10 
18*000 
17*750 
0*250 
0*010 
0*260 
10 
18*180 
17*917 
0*263 
0*010 
0*273 
10 
21*382 
21*116 
0*266 
0*011 
0*277 
10 
23-202 
22*919 
0*283 
0*013 
0*296 
10 
25*331 
25*045 
0*286 
0*014 
0*300 
t . 
B-ri 
t . 
B-ri 
t . 
B - t . 
t . 
B - t . 
0 
0*11 
7 
0*19 
14 
0*25 
21 
0*28 
1 
0*12 
8 
0*20 
15 
0*25 
22 
0*29 
2 
0*13 
9 
0*21 
16 
0*26 
23 
0*30 
3 
0*14 
10 
0*23 
17 
0*26 
24 
0*30 
4 
0*16 
11 
0*25 
18 
0*26 
25 
0*30 
5 
0*17 
12 
0*25 
19 
0*27 
6 
0*18 
13 
0*25 
20 
0*28 
* Annales de Chimie, 1836, tome Ixiii. p. 368. 
t Ibid. 1837, tome Ixiv. p. 312. 
X Jahresbericht der Miinchener Sternwarte fiir 1852, S. 64, 93, 101 ; and Aimalen fiir Meteorologie, 1842, 
Heft iv. S. X. XV. 
