346 
unit of heat being, for instance, the quantity required to raise 1000 
lbs of water by th of a degree in temperature. 
The same system of reduction applied to the observations con- 
tinued at the Calton Hill station, has led to results from which the 
following; are selected : — 
Average annual term for 12 years — 1842 to 1854 — Trap rock 
to Calton Hill. 
Col. 1. 
Col. 2. 
Col. 3. 
Col. 4. 
Col. 5. 
Depths below 
surface in 
French feet. 
Proportionate 
Diminution 
of amplitude. 
Diminution of 
Napierian loga- 
rithm of ampli- 
tude per French 
foot of descent. 
Retardation 
of epoch in 
circular 
. measure, 
per Fr. foot 
of descent. 
Retardation 
of epoch 
in decimal 
of a y ear, 
per Fr. foot 
of descent. 
Retardation 
of epoch 
in days, 
per Fr. foot 
of descent. 
3 feet to 6 feet 
•67 5 
T310 
•1233 
6 „ 12 ,, 
•498 
T163 
T14-2 
12 „ 24 „ 
•260 
T121 
T145 
3 „ 24 „ 
»0 
JO- 
OO 
© 
T160 
•1157 
•01841 
6*724 
By these results it will be seen that the discrepancies from the theory 
based on the hypothetical conditions of uniformity, noticed above as 
found in the reduction of the first five years’ series of observations, are 
maintained with the same character, and to nearly the same amount, 
in the succeeding series of thirteen years. An investigation of the 
changes of conductivity and specific heat, which, if the ground were 
level and the surface uniform, would be required to account for these 
discrepancies, is made, so far as the data suffice for determining them. 
The paper concludes with the solution of some practical problems 
regarding the conduction of heat through rock possessing the con- 
ductivity determined by the reductions which form the chief part of 
the paper. 
4. On a Method of Reducing Observations of Underground 
Temperatures, with its Application to the Monthly Means 
recorded in the Report of the Royal Observatory of Edin- 
burgh, &c. By Professor Everett. 
In this paper the same general method of reduction as that of 
Professor Thomson, explained in the preceding paper, is followed. 
The numerical labour is, however, much diminished by using the 
monthly means given in the observatory report as data for twelve 
