ON THE RATE OF INCREASE OF UNDERGROUND TEMPERATURE. 49 
strongly support Dr. Stapff’s deduction as against the deduction given in 
the ‘Summary ;’ the actual increase from the surface to the tunnel in 
this part being at a much more rapid rate than 1° F. in 57:8 feet— 
namely, at 1° F. in 38 feet. 
As a guide for future estimates, it may be noted that the correcting 
factor for reducing 85 feet to 57:8 feet is almost exactly 2; but if we 
compare the result merely with the observed increase beneath the crest of 
the mountain, which was 1° F. in 100 feet, the correcting factor to be 
applied to 100 feet is ‘58. 
If we assume 1° in 57:8 feet as the rate for the St. Gothard Tunnel, 
and also for the Mont Cenis Tunnel, instead of the rates assumed in the 
‘Summary,’ the effect upon the general mean for all places will be to 
make it 1° F. in 60 feet, instead of 1° F. in 64 feet. 
[Dr. Stapff’s paper has heen printed in extenso, with the Andermatt 
observations as an Appendix, in the Transactions of the North of England 
Mining Institute for 1883. ] 
Report of the Committee consisting of Captain ABNEY, Professor 
STOKES, and Professor SCHUSTER (Secretary), appointed for the 
purpose of determining the best Experimental Methods that can 
be used in observing Total Solar Eclipses. 
Tue Committee has considered it advisable to adjourn its discussion 
until the results of the last total solar eclipse should be known. As the 
eclipse expedition which went out to observe that eclipse has returned 
only a short time ago, the Committee desires its reappointment without 
grant of money. 
Report of a Committee, consisting of Protessors G. H. Darwin and 
J.C. Apams, for the Harmonic Analysis of Tidal Observations. 
Drawn up by G. H. Darwin. 
Preface.—Account of Operations. 
A comMITTEE appointed for the examination of the question of the 
Harmonie Analysis of Tidal Observations practically finds itself en- 
gaged in the question of the reduction of Indian Tidal Observations ; 
since it is only in that country that any extensive system of observation 
with systematic publication of results| exists. This at least has proved 
to be the case with our committee. On communication with General 
Strachey, it was found that the India Office was anxious to obtain 
advice as to the reduction of observations and publication of results, 
and that Major A. W. Baird, R.E., the officer in charge at Poona of the 
Tidal Department of the Survey of India, felt the desirability of instruc- 
1 Indian Tide Tables, published by authority of the Secretary of State. 
1883. E 
