rous periods and ceased with the Permian.
When again the volcanic forces became active, it was in the early
Tertiary era; the evidences for this lie outside the English border.

The principal directions of crust movement in England are: (1) north
and south, by which the Pennine folds and faults, and the Malvern
Hills have been produced; (2) east and west, by which the folds of the
Weald and the Mendip Hills, and those of Devonshire have been formed.
Another less important direction is N.W. and S.E., as in the Charnwood
folding.

Further details of the geology are given under the heads of the
counties. (J. A. H.)

IV. CLIMATE

Climate.

_Temperature._--The mean annual temperature of the whole of England
and Wales (reduced to sea-level) is about 50 deg. F., varying from
something over 52 deg. in the Scilly Isles to something under 48 deg.
at the mouth of the Tweed. The mean annual temperature diminishes very
regularly from south-west to north-east, the west coast being warmer
than the east, so that the mean temperature at the mouth of the Mersey
is as high as that at the mouth of the Thames. During the coldest
month of the year (January) the mean temperature of all England is
about 40 deg.. The influence of the western ocean is very strongly
marked, the temperature falling steadily from west to east. Thus while
the temperature in the west of Cornwall is 44 deg., the temperature on
the east coast from north of the Humber to the Thames is under 38
deg., the coldest winters being experienced in the Fenland. In the
hottest month (July) the mean temperature of England and Wales is
about 61.5 deg., and the westerly wind then exercises a cooling
effect, the greatest heat being found in the Thames basin immediately
around London, where the mean temperature of the month exceeds 64
deg.; the mean temperature along the south coast is 62 deg., and that
at the mouth of the Tweed a little under 59 deg.. In the centre of the
country along a line drawn from London to Carlisle the mean
temperature in July is found to diminish gradually at an average rate
of 1 deg. per 60 m. The coasts are cooler than the centre of the
country, but the west coast is much cooler than the east, modified
continental conditions prevailing over the North Sea. The natural
effect of the heating of the air in summer and the cooling of the air
in winter by contact with the land