REPORT ON METEOROLOGICAL OBSERVATIONS, WISLEY, 1917. 327 
Mean relative humidity of the air at 9 a.m. (complete saturation being repre- 
sented by 100), 81 per cent. 
Rain fell on 22 days, to the total depth of 4-04 in. (equivalent to about 19 
gallons of water to the square yard) . Heaviest fall on any day 1 -22 in., on the 1st . 
The prevailing winds were at first north-westerly, then from south-west. 
The average velocity of the wind was 7 miles an hour. 
There were 171 hours of bright sunshine, equal to 38 percent, of the greatest 
possible amount. 
There was but one entirely sunless day. 
September. — Like its immediate predecessor, this month was a very 
windy one, the prevailing direction of the wind being westerly, and its 
chief characteristic its gustiness rather than its exceptional strength, 
the force of a gale being seldom reached. But in contrast to the very 
wet August it was a dry month, the rainfall being as a rule much below 
the average, although in a few districts there were exceptions, owing 
to thunderstorms and heavy local rains, which, however, only affected 
very limited areas. But, like August, it was again a moderately warm 
month, and owing to a similar cause — the high average daily tempera- 
ture being due to exceptionally warm nights rather than to very hot 
days. But in most districts the fresh, gusty, westerly wind proved 
to be very useful to the agriculturist, enabling him to dry his corn after 
the soaking the stooks had in the drenching downpours of August ; 
so that on the whole the weather of the month may be fairly sum- 
marized as having been seasonable, and good for harvest, and indeed 
all operations on the land. There was again rather less than the average 
amount of sunshine, but this was less noticeable at Wisley, and indeed 
over the whole of southern and south-eastern England, than in the 
northern parts of the kingdom ; and the generally favourable climatic 
conditions of the month, from the horticulturist's point of view, was 
evidenced by the quite unusual progress which continued to be made 
by all out-door plant life throughout. 
The observations made at Wisley are summarized in the following 
table : 
Mean temperature of the air in shade .... 58-6° 
Highest ,, ,, ,, . . 75 0 on the nth 
Lowest ,, ,, ...... 41 0 „ 28th 
Lowest ,, on the grass . . . 28 0 ,, 28th 
Number of nights of ground frost ...... . . 2 
At depth of 
I ft. 2 ft. 4 ft. 
Mean temperature of the soil at 9 a.m. . . . 59- 8° 59- 8° 58-6° 
Highest „ „ 62 0 6i° 59 0 
Lowest „ 56 0 58 0 58 0 
Mean relative humidity of the air at 9 a.m. (complete saturation being repre- 
sented by 100), 84 per cent. 
Rain fell on 12 days, to the total depth of 1*50 in. (equivalent to about 
7 gallons of water to the square yard). Heaviest fall on any day 0-37 in., on the 
17th. 
The prevailing winds were south-westerly. 
The average velocity of the wind was 5 miles an hour. 
There were 57 hours of bright sunshine, equal to 46 per cent, of the greatest 
possible amount. 
There were three days on which no sunshine was recorded. 
October. — Taking a broad view of the weather of this month it may 
be summarized as windy and wet, with a mean temperature consider- 
