CLIMATIC FACTORS. lvii 
In April of that year, on the 4th, the temperature 
fell to 25°6°, and next day it rose to 45°6°—a range 
of 20° in two days. Next to sudden changes of 
temperature, high winds affect vegetable growth. 
Fortunately our strong gales occur during the winter 
months, and the more moderate during the other 
seasons. Vegetation on exposed hill-sides and on 
low-lying islands is of stunted growth. Calwna, 
Empetrum, and other plants show in some cases 
lines of exposed stems and roots where the wind has 
not only withered the plants but carried off some of 
the soil from the roots. These things are seen on the 
west and south-west hill-sides. <A gale is reckoned by 
the Meteorological Office as having a velocity of 40 
miles or upwards, and these are frequent. 
MEANS OF OBSERVATIONS IN ORKNEY 
For 33 YEARS—1873-1905. 
Days on 
Snowy which Thunder Clear 
Rainy days. days. hailfell. storms. sky. Overcast. Gales, 
Ee ete Ge or.) Lae a GY ak) aly cee SEG ae gD 
The mean annual rainfall is 37 inches, and the 
mean annual sunshine is 1185 hours, which compares 
favourably with Edinburgh—1164 hours. Winter 
gales reached their maximum in November 1893, 
with a velocity of 96 miles. The summer maximum 
occurred in June 1890, with a maximum velocity of 
75 miles. This dreadful gale caused vegetation every- 
where, but especially cereals, to put on a yellowish, 
withered appearance, as if the crops were partially 
destroyed; but the grain was not in ear, and the 
broad leaves alone suffered. In a few weeks the 
earth was once more clothed in a mantle of green. 
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