OBSERVATIONS OF UNDERGROUND TEMPERATURE. 419 
26. By taking, for each depth, the coefficients A,, B, (not explicitly shown 
above), derived from the first five years’ average, and multiplying by 5; taking 
similarly the coefficients A,, B,, for the succeeding thirteen years’ average, and 
multiplying by 13; adding each of the former products to the corresponding one 
of the latter, and dividing by 18; we obtain, as the proper average for the whole 
eighteen years, the values shown in the following table, in the columns headed 
A,, B,. The amplitudes and epochs shown in the next columns are deduced 
from these by the formulz Ni (A,? + B,?) and tan > respectively,— 
1 
TABLE VII.—ANNUAL HARMONIC VARIATION OF TEMPERATURE IN CALTON HILL, 
FROM 1837 To 1844 INCLUSIVE. 

A Amplitudes in .Epochs in degr 
els Ta degrees Fahr. In degrees Fahr. degrees Fahr. Fad Pinte, = 
3 feet —5'184 — 4-989 71949 
6 feet — 2-080 —4:416 4'8812 
12 feet + ‘5961 — 2°3345 2°4094 
24 feet + °6311 + 0306 |, ‘6319 

From these, as before, for ten terms of five years and of thirteen years sepa- 
rately, we deduce the following :— 
TABLE VIIIL—AVERAGE OF EIGHTEEN YHARS, 1837 To 1844; Trap Rock or 
CALTON HILL. 










Retardation of Epoch 
in Circular Measure, 
per French foot of 
Descent. 
Diminution of Loga- 
rithmic Amplitude 
per French foot of 
Descent. 
Depths below surface, 
in French feet. 








3 to 6 feet. -1286 on DAIL 5) 
Gols, 1177 ‘1150 
12 to 24 ,, ‘1115 1141 
3 to24 feet. °1157 +1154 
27. Hence, we have as final means, of effects on logarithmic amplitudes and 
on epochs, for the average annual variation on the whole period of eighteen 
Zs, — 
1. From depth 3 feet to 6 feet, : : 5 1250 
2. + nee 6 ee , 2 1163 
SO BG Ona eas pe eee cori og 
If now, in accordance with the proposed plan, we measure depths, not in constant 
