48 REPORT—1883. 
eight hours in the hole, besides three hours allowed before insertion ; 
whereas in the previous observation (1881 Report) it was only left six 
hours in the hole, with ten or fifteen minutes before insertion. Assuming, 
as before, a surface temperature of 49°, we have an increase of 35° in 
2,880 feet, which is at the rate of 1° in 82 feet. 
Mr. Garside has also furnished the results of one year’s observations 
of surface temperature at two stations in Ashton-under-Lyne, in the 
immediate vicinity of the pits in which his observations have been taken. 
One station is Croft House, in the centre of the town, 545 feet above sea- 
level ; and the other is the District Infirmary, 501 feet above sea-level. 
In both cases the data furnished are the monthly. means, for the year 
1882, of daily observations of the temperature of the soil at 4 feet deep 
and 1 foot deep; also of the maximum and minimum temperatures of 
the air. The annual mean for the thermometer 4 feet deep is 47°°5 at 
Croft House, and 45°-9 at the Infirmary. For the thermometer 1 foot 
deep the numbers are 46°°2 and 45°°6; and for the half-sum of maximum 
and minimum 48°:4 and 46°6. Unless the year 1882 was exceptionally 
cold, our assumption of a surface temperature of 49° would therefore 
appear to be in excess of the truth; but farther time must be allowed to 
settle this question. 
The Secretary has been consulted by the Trustees of the Lick 
Observatory, about to be erected on a mountain in California, as to the 
advisability of taking observations of underground temperature there, 
and the best method to be followed. He has recommended observations 
at various points for comparing the temperature at 3 feet deep with the 
temperature of the air. 
One inverted Negretti-maximum and two slow-action thermometers 
have been entrusted to Mr. T. W. Edgeworth David, Assistant Field 
Geologist to the Mining Department in New South Wales; and two 
slow-action thermometers have been supplied to the Engineering Depart- 
ment of the South-Eastern Railway, for observations in the Channel 
Tunnel. 
Since the publication of the ‘Summary,’ which accompanied last 
year’s Report, the Secretary has received from Dr. Stapff a communica- 
tion which renders an important modification necessary in the results for 
the St. Gothard and Mont Cenis Tunnels. In the ‘Summary’ a con- 
jectural correction was applied for the convexity of the mountain surfaces. 
Dr. Stapff’s calculations lead to the conclusion that a much larger allow- 
ance must be made under this head. He deduces 1° F. in 85 feet as the 
actual average rate of increase from the surface overhead to the tunnel ; 
and he calculates that at a depth below the tunnel sufficient to make the 
isothermal surfaces sensibly plane, the increase is 1° F, in 57°8 feet. His 
method of calculation is very elaborate and laborious. He first divides 
the whole length of the tunnel into sections, and, assuming that the 
isotherms are parabolas, investigates the parabolic isotherm for each 
section. Then, by combining these, he deduces a general law for the ~ 
whole length, and infers that at the depth at which the isotherms are 
flattened out into straight lines the rate of increase is 1° F. for 57'8 feet 
of descent. 
As a check upon this very elaborate method, the secretary requested 
Dr. Stapff to furnish him with the actual observations both above 
ground and in the tunnel, for that portion which passes under the plain 
of Andermatt, This Dr. Stapff has kindly done, and these observations 
