is largely masked in England on
account of the strength of the prevailing south-westerly wind carrying
oceanic influence into the heart of the country. This effect is well
seen in the way in which the wind blowing directly up the Severn
estuary is directed along the edges of the Oolitic escarpment
north-eastward, thus displacing the centre of cold in winter to the
east coast, and the centre of heat in summer to the lower Thames, from
the position which both centres would occupy, if calms prevailed, in a
belt running from Birmingham to Buckingham. As to how far the narrow
portion of the North Sea modifies the influence of the European
continent, there seems reason to believe that the prevailing winds
blowing up the English Channel carry oceanic conditions some distance
inland, along those parts of the continent nearest to England. The
Mersey estuary, being partly sheltered by Ireland and North Wales,
does not serve as an inlet for modifying influences to the same extent
as the Bristol Channel; and as the wind entering by it blows squarely
against the slope of the Pennine Chain, it does not much affect the
climate of the midland plain.

[Illustration: Map of ENGLAND & WALES--Section II.]

_Winds._--The average barometric pressure over England is about
29.94 in., and normally diminishes from south-west to north-east at
all seasons, the mean pressure on the south coast being 29.97 and that
on the northern border 29.88. The pressure at any given latitude is
normally highest in the centre of the country and on the east coast,
and lowest on the west coast. The direction of the mean annual isobars
shows that the normal wind in all parts of England and Wales must be
from the south-west on the west coast, curving gradually until in the
centre of the country, and on the east coast it is westerly, without a
southerly component. The normal seasonal march of pressure-change
produces a maximum gradient in December and January, and a minimum
gradient in April; but for every month in the year the mean gradient
is for winds from southerly and westerly quarters. In April the
gradient is so slight that any temporary fall of pressure to the south
of England or any temporary rise of pressure to the north, which would
suffice in other months merely to reduce the velocity of the
south-westerly wind, is sufficient in that month to reverse the
gradient and produce an east w