574 Proceedings of the Royal Society 
ture of the earth at the bottom, from 500 to 600 feet under the sea- 
level, should be by theory about 60° in the deepest parts; but, con- 
sidering the very low conducting power of the rocky structure of the 
earth, its heating power over so vast a bed of cold water must be 
very feeble. The sun’s rays are at once the most energetic heating 
power, that which penetrates deepest, and that which alone can 
sensibly heat any part of the superstratum of water underneath 
the thin bed near the surface, where it is aided by the warmth of 
the atmosphere, and the stirring of the water by the wind. But 
there is a limit to the sun’s penetration in such depths, when the 
water, as in the case of Loch Lomond, is coloured, however slightly. 
It has been imagined that the presence of springs at the bottom 
may be a fourth source of influence over the temperature. If there 
be any springs there, the effect must be to heat the water. But, as 
there are no springs in Scotland which rise above the surface, or pre- 
sent other proofs of owing their place to unusual sources of pressure, 
it seems most improbable that any are so constituted as to overcome 
the pressure which exists at the bottom of a very deep lake. 
Every known consideration, — the great thickness of the cold 
substratum, its steady low temperature, and its greater colour than 
at the surface — contributes proof that this substratum can undergo 
little or no movement, unless an unusually hard winter should dis- 
place it by colder water from above.*] 
The previous observations have extended to so great a length 
that I must postpone till another opportunity the remarks which I 
have prepared on the third of my promised topics — the Action of 
Water on Lead. 
The following Gentlemen were elected Fellows of the 
Society : — 
Alexander H. Lee, Esq., C.E. 
Robert Lee, Esq., Advocate. 
John Anderson, LL.D. 
* While the preceding statements were passing through the press, my 
attention was called to similar observations in Sir John Leslie’s article on 
Climate in the “Encyclopaedia Britannica,” by Saussure on the Lakes of 
Geneva, Thun, and Lucerne, and by the late eminent engineer, Mr James 
Jardine, on Loch Lomond and Loch Katrine in 1814. Their observations 
are not entirely concordant with those given above. I contemplate further 
observations which may reconcile them. 
