INTRODUCTION. XXXI 
ADIE and Son were desired to make a thermometer, whose bulb rested in a cup in 
a brass bar of the same dimensions as the magnet, and covered loosely by a small 
brass cap.* The following comparisons were made of the indications of the two 
thermometers, the box being in its original state, and the rise of temperature con- 
siderable. 
TABLE 12.—Comparisons of the Thermometers with the Bulb free, and with the 
Bulb in a brass cup. 
| 
Géttingen | Thermometer. Tikeconee: 
Mean Time, | 
Loss. Adie. 
1844. 3 3 ° 
da: ie 
Jan. 2 21 30-9 30-7 0-2 
22 31-3 31-0 0:3 
23 319 31-5 04 
0 33.9 33-0 0-9 
1 38.9 37-6 1-3 
2 42-3 410 1-3 
3 44-7 43.0 1-7 
4 45-6 44.0 1-6 
5 45-9 44-5 1-4 
6 46-0 44.9 1-1 
7 46:1 45.0 1-1 
8 45-9 44.9 1-0 
11 450 44.3 0-7 
34. No observations have been made to determine the effect of the copper ring 
or damper. It must, however, be small. 
During terms, and generally during magnetic disturbances, the temperature is 
noted at the beginning of each hour; the corrections for observations between the 
hours are interpolated from those at the beginning of the hours. 
ABSOLUTE HorIzonTaL INTENSITY. 
35. An observation of absolute horizontal intensity was made by Mr Russet, 
March 26. 1842. It is given, page 66, with the particulars of reduction. 
As there was no extra declinometer, it was necessary to endeavour to eliminate 
the changes of declination, by reversing the magnet. On account of the imperfec- 
tions of this method, no other observations were made till 1843, when an extra in- 
strument was obtained. 
* It was my original intention to enclose the bulb of the thermometer in a metallic capsule (from 
which this differs little), but it was difficult to determine the thickness of the capsule. Professor 
Lioyp, to whom I wrote, informed me that he had already adopted the precaution, having obtained a 
brass bar of the dimensions of the magnet, containing a small iron cup with mercury, 
in which the 
bulb of the thermometer was placed. 
