‘i i ie 
ON UNDERGROUND TEMPERATURE. 513 
Depth. Temperature. Mean Temp. Difference per foot. 
347 ft. «B65 
il BAT bites Visio 53-69 
Ss 53-72 °. 
300 52°77 001979 
i, BPD eweeece. 52:76 . 
" 52-80 001967 
a 2 ed saree cease 
D a 0-01800 
180 50-49 tp 2 
; safer beeserapet 
120 49-20 0-02133 
ry rc 49-29 
ik 49-20 002117 
60 47-95 
. ieee \ (ies 47-95 
In all the observations taken with this thermometer, it was allowed to 
remain a day or two at least at each depth before being raised. 
The thermometer was next removed to a second bore, at a short distance 
from the former, which was originally 95 fathoms deep, but had become 
filled up with sediment 45 fathoms, leaving only 50 fathoms free. Observa- 
tions were made from early in March till the middle of April; the results 
from the greatest depths were pretty constant, but towards the surface they 
varied from time to time, occasioned in all probability by a constant flow of 
surface-water into the pipe, which found an escape at some unknown depth. 
The weather was generally wet, and there was always more or less entering 
the pipe, affected by the temperature of the air. 
It is considered that the thermometer acted very satisfactorily at the 
depths at which it was used; but it is doubtful if its indications could be 
relied on for considerably greater depths, on account of the time taken to 
wind it up; and the speed could not be safely increased, particularly if the 
bore has rough projections on its sides. An instance of this occurred in the 
middle of April. While raising the thermometer with considerable velocity, 
it stuck, and would neither move up nor down; it had to be left till means 
were got to detach it gently from the obstruction; and when brought to 
the surface, the upper part of its strong casing was half torn away, but the 
thermometer itself quite safe. 
With the view of obviating this difficulty, and of observing more rapidly, 
trials were being made at bore No. 1 with a thermo-electric junction of in- 
sulated copper and iron wire, let down to various depths, and the other 
junction placed in a vessel of water, which was heated or cooled, till a gal- 
vanometer showed no current, when the temperature was taken. Small 
discrepancies existed between the results thus obtained and those previously 
_ got directly with the thermometer ; but there has not been time hitherto to 
ascertain their cause. The chief difficulties to be overcome were the want 
of a steady stand for the galvanometer (one of Sir Wm. Thomson’s delicate 
mirror galvanometers), and the means of obtaining sufficient darkness to be 
able to read it. 
A third method has been tried, which promises to give satisfactory results, 
Two of Phillips’s maximum thermometers were furnished by Casella; but 
unfortunately on the second day of trial they met with an accident, and had 
to be returned to London to be repaired, and have only just now been re- 
