254 
DR. A. A. RAMBAUT ON UNDERGROUND TEMPERATURE AT OXEORD 
For a second thermometer we have similarly 
P»' = A n e- aM ' and E,/ = (3 n x + y, 
and, therefore, 
and 
(/)• 
Thus from each wave as observed at any pair of thermometers, we obtain two 
determinations of the value of k, one from the diminution of amplitude, and the 
other from the retardation of phase. 
In computing the value of x /tt/k I have expressed the depths in Paris feet, in 
order to bring out the results in terms of the same units as those employed by 
Professor Everett in his Reduction of the Greenwich Observations^ and those of 
Lord Kelvin already referred to. The results are given in the following tables :— 
Values of deduced from the Annual Wave. 
Thermometers 
Erom diminution 
From retardation 
compared. 
of amplitude. 
of phase. 
No. 5 and No. 4 
0-1222 
0-1202 
5 ^ 
T212 
T181 
„ 5 „ 2 
T208 
T181 
n 4 ,, 3 
T191 
T141 
4 2 
T193 
T159 
3 2 
T1S6 
T178 
Means. . . 
0-1204 
0-1174 
Mean of both . . . 0T189 
The values deduced from the half-yearly wave in a similar way, are as follows:— 
* ‘ Greenwich Observations,’ 1860 (cxciii). 
