12 BRITISH PLANTS 
picked up in their journey over a wide stretch of sea. 
This oceanic type of climate prevails over western Europe 
and the British Isles. Owing to the humidity of the 
atmosphere, the winters in these regions are mild and 
the summers cool. Regions remote from the sea have 
a continental type of climate, in which the dryness of the 
atmosphere leads to extremes of temperature, the summers 
being very hot and the winters very cold: such is the 
climate of Russia and the interior of Canada. 
3. Proximity to Highlands and Mountain Ranges.— 
Highland masses cool the air-currents, and much of 
their contained moisture is consequently condensed to 
liquid water, and falls as rain. There is a “ wet” and 
a “dry” side to mountain chains; the side facing the 
direction of the prevailing winds is wet, for the air- 
currents, following the rising gradients of the ground, 
become cooled and gradually damper, the excess of 
moisture falling as rain ; as the currents descend on the 
other side, they become warmer and drier. Places 
situated on the “lee ”’ or dry side are said to lie in the 
rain-shadow of the mountains. A good example of this 
is Bray, a watering-place near Dublin, which lies in the 
rain-shadow of the Wicklow Hills. Though on the sea- 
coast, it is one of the driest spots in Ireland. In the 
same way, the desert of Atacama is a rainless region 
lying along the coast of Chili in the rain-shadow of the 
Andes. 
Elevated plains, especially when they are very ex- 
tensive, as in Spain and India, are usually very dry, and 
subject to wide extremes of temperature. The winds 
that blow over them lose most of their moisture while 
they are ascending the flanks. The latter, being exposed 
to the falling rain, are richly clothed with vegetation, 
whilst the plateaux themselves are grassy plains or 
semi-deserts. 
4. Direction of the Prevailing Winds.—If these have 
passed over a broad expanse of water, they will be moist ; 
if, on the other hand, they have travelled over a great 
land-surface, they will be dry. Again, winds blowing 
from the north are cold and dry, while those which come 
from the south are warm and moist. North winds blowing 
southwards must gradually become warmer, and, if at 
the same time they are travelling over a wide land- 
