METEOROLOGICAL OBSERVATIONS MADE AT WISLEY. 51 



which not only shut off the sun's rays by day, and thus prevented the 

 temperature from rising to its normal height, but at night served as a 

 screen to prevent loss of heat by radiation from the earth's surface, 

 and so maintained throughout the night an unusual degree of warmth. 

 The result was a mean temperature for the month considerably higher 

 than is usual in March ; at Wisley the screened thermometer never 

 fell to the freezing point all through the month, a rare occurrence for 

 the third month of the year ; there were, however, a few sharp ground 

 frosts, and in the northern parts of the Kingdom the weather was, as 

 might have been expected, somewhat colder than over the southern 

 counties. But the month was a stormy one, with an abnormally large 

 rainfall which in some parts of the country amounted to considerably 

 more than double the average amount. In some of the gales the wind 

 blew very strongly, and associated with one which passed over the 

 country about the close of the third week severe thunderstorms were 

 experienced over a large part of southern England, accompanied in 

 several districts by snow and hail, the snow disappearing, however, 

 very quickly ; the general direction of the wind all through the month 

 was from between south and west. The most northern portion of the 

 Kingdom was the most favoured in the matter of sunshine, but at 

 Wisley the average daily amount was but three hours, which is less 

 than 30 per cent, of the possible amount. 



The results from the observations made at Wisley are shown in 

 the following table : 



M arch. 



■ o 



Mean temperature of the air in shade . . 46-5 



Highest temperature of the air in shade . 59*9° on the 25th 



Lowest temperature of air in shade . . 32 '4° on the 21st 



Lowest temperature on the grass . . . 23*2° on the 21st 



Number of nights of ground frost . . 14 



Mean temperature of the soil at 9 a.M. . 

 Highest temperature of the soil at 9 a.m. 

 Lowest temperature of the soil at 9 a.m. 



At 



depth 



of 



1 it. 



2 ft. 



4 ft 



45-3° 



45-i° 



459° 



51-2° 



47-6° 



47'i° 



42-3° 



43-3° 



45'4° 



Mean relative humidity of the air at 9 a.m. (complete saturation 

 being represented by 100), 86%. 



Rain fell on 22 days, to the total depth of 2-96 inches (equivalent 

 to about 13I gallons of water to the square yard). Heaviest fall on 

 any day 0-58 inch, on the 4th. 



The prevailing winds were from between south and west. 



The average velocity of the wind was 10 J miles an hour. 



There were 98 hours of bright sunshine, equal to 27 per cent, of 

 the greatest possible amount. 



There were 3 days on which no sunshine was recorded. 



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