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times ; at 3 p.m. fourteen times. The temperature of the 
air rose more than half the days above freezing in the mid- 
dle of the day, though only in a few exceptional cases above 
that point in the morning. This winter has, therefore, 
been an unfavourable one for my observations, as it is here 
quite an exception for the air to rise so often above freezing 
in the winter months. The tin of ice was weighed daily (at 
11 a.m.) with a first rate beam 47 cm. long, made by Young 
& Son, of London, and guaranteed to weigh 5 Kilo., and it 
turned with a twentieth of a gramme. 
*The evaporation from the ice inDecember was 12-24 mm.; 
January 15*27 mm.; February 15-018 mm. 
The smallest amount which I have had to measure in the 
twenty-four hours was 0*084 mm., Dec. 13th, during which 
time the temperature varied from 26*6° F. to about 19° F., 
with hardly any wind ; the largest amount with ice in the 
tin all the time was 0-88 mm. on Dec. 11th, the temperature 
rising to 35*7 at 11 a.m., but until about 8 a.m. the tem- 
perature must have been moderately below freezing; on 
the night of the 10th there was a considerable wind. Once 
(Nov. 28th), with the tin full of water, the evaporation was 
2*314 mm., but then the temperature was high all the time, 
rising to 47° F., yet there was very little wind. 
This winter has not been favourable for comparing the 
evaporation of snow with that of ice, but I think the results 
obtained seem to be, that when the tin is filled with snow 
the evaporation is for the first day or two about 10 per cent 
more than that of water, it then becomes more consolidated 
and evaporation in both is about equal. 
On one occasion I buried a tinful of snow up to the rim 
*1 find that when there is water in the tin the temperature lags 
very much behind that of the air, there being sometimes as much as 
5° to 8° F. difference between the air and water. This must always be a 
cause of difficulty in measuring evaporation, and therefore for comparison 
the depth of water should always be the same, and perhaps the quantity 
I used (viz. two inches) was too large. 
