REPORT ON METEOROLOGICAL OBSERVATIONS, WISLEY, 1917. 319 
ceptibly) upon the frozen ground becomes at once congealed, and 
covers everything with a coating of clear ice. 
The results of the observations made daily at the Climatological 
Observatory in the Society's Gardens at Wisley are shown in the 
following table : 
Mean temperature of the air in shade .... 35- 1° 
Highest 53 0 on the 1st 
Lowest .. 20 0 „ 30th 
Lowest on the grass . . . . . 7° ,, 3°th 
Number of nights of ground frost . . . . . . . 26 
Mean relative humidity of the air at 9 a.m. (complete saturation being repre- 
sented by 100), 91 per cent. 
Rain or snow fell on 13 days, to the total depth of 1*05 inches (equivalent to 
about 5 gallons of water to the square yard). Heaviest fall on any day 0-28 in., 
on the 5th. 
The prevailing winds were at first westerly ; then from north-east and east. 
The average velocity of the wind was 8 miles an hour. 
There were 38 hours of bright sunshine, equal to 15 per cent, of the greatest 
possible amount. 
There were 16 days on which no sunshine was recorded. 
February. — The weather generally experienced over the United 
Kingdom during the greater part of this month was just a continuation 
of the Arctic conditions of January, but they were of even greater 
intensity and spread themselves over a rather larger area. Again 
it was dry, but at the same time very dull over the greater part of 
the kingdom, and during the first few days the cold was more intense 
than at any time in January, or indeed for many past winters. At 
Wisley the average temperature in the screen (four feet above the 
ground) was 34 0 Fahr., instead of 40 °, which is the usual average 
for the month ; but on the ground the fully exposed thermometer 
once fell to 4 0 below zero (36 0 below the freezing-point), and on the 
warmest night of the month the temperature was no higher than 
37 0 Fahr., conditions which are without parallel in the records hitherto 
obtained at the Gardens. The wind, too, was as keen and biting 
as in January, and was responsible for much damage to vegetation ; 
at Wisley " all vegetables suffered very much, many appearing 
as though they had been seared by fire ; whilst trees and shrubs were 
likewise much injured by the bitter winds and a similar experience 
was fairly general over a large portion of the kingdom : e.g. in the 
West of Ireland, " hundreds of birds were killed by the intense cold 
and want of food ; " in the English Midlands, " evergreens, such as 
yew, laurel, holly, and ivy, were scorched by the frost and in Devon, 
on the southern edge of the Dartmoor region, " the frost lasted con- 
tinuously for 91 days, . . . and nearly all the furze was killed." To 
find a parallel for duration and intensity one must go back at least 
to 1895, but the Dartmoor record claims to have been the longest 
continuous frost for sixty-two years. At Wisley, up to the middle 
At depth of 
1 ft. 2 it. 4 ft. 
Mean temperature of the soil at 9 a.m. . 
Highest ,,, 
Lowest 
