28 
Proceedings of the Royal Society 
any consequence whatever at the time to this difference. It 
might have been an error of observation ; but three competent 
observers agreed in marking the index as at 42°-l. I had unhappily 
no opportunity of making any observation during the remaining 
summer months, which I now greatly regret. But on 8th August 
I went from Loch G-oil to visit Dr Bennett at Loch Lomond, and 
with his assistance as an observer, got the following results, with 
the same thermometer as in former observations, viz., near the 
surface, 61 0, 5 ; at 200 feet, 44° ; at 250 feet, 42°*6 ; at 300 feet, 
42°*5 ; at the bottom, in 594 feet soundings, 42°-5. I returned on 
22d August, and again, with Dr Bennett’s check, obtained at the 
surface, 64°*5 ; at 300 feet, 42°*5 ; at 600 feet, 42 0, 4. A third time I 
returned on 19th September, and obtained at the surface, 57°*0 ; at 
200 feet, 43*0°; at 582 feet, at the bottom, 42 -66. 
Here then is an appreciable rise, — as to which I know not where 
a mistake can exist, — since the autumn of lagt year, and taking 
place during the warm months only. 
It would be rash to draw deductions from the observations 
alone of two such autumns as those of 1871 and 1872, the one 
following a rather hard, the other an uncommonly open winter. 
But do not these observations establish some hope that a single 
good observation, made, let us say, in the middle of August, of 
September, and of October, may be found to denote the relative 
quality of our winters, and to mark out cycles of it ? 
Everything here depends on the fidelity of the observer and 
the accuracy of his instrument. On this account, and for the sake 
of those who, I trust, will repeat these observations from year to 
year, I have to remark that the thermometer I used was always 
the same, a protected thermometer, by Casella, instrument-maker 
to the Admiralty ; that its scale at 60° and 40° agreed exactly with 
three others intended by their respective makers to be exact, one of 
them, indeed, made by Casella himself ; and that I had an oppor- 
tunity of ascertaining two days ago, that it is proof against 
pressure, in an excellent machine, constructed for Professor 
■Wyville Thomson’s expedition by the able engineer Mr Milne. 
Marking 55 o, 0 in the air, it came out after being exposed to a 
pressure equivalent to that of 3000 feet of water, marking 66° by 
the mercury in both limbs ; and in the minimum side the index 
