We may conclude that the
absence of corals higher than the north of England implies a more
temperate climate further north, but what Sir A. Geikie calls
(with slight exaggeration) "the almost tropical aspect" of
Greenland warns us to be cautious. The climate of the
mid-Jurassic was very much warmer and more uniform than the
climate of the earth to-day. It was an age of great vital
expansion. And into this luxuriant world we shall presently find
a fresh period of elevation, disturbance, and cold breaking with
momentous evolutionary results. Meantime, we may take a closer
look at these interesting inhabitants of the Middle Ages of the
earth, before they pass away or are driven, in shrunken
regiments, into the shelter of the narrowing tropics.
The principal change in the aspect of the earth, as the cold,
arid plains and slopes of the Triassic slowly yield the moist and
warm ow-lying lands of the Jurassic, to consists in the character
of the vegetation. It is wholly intermediate in its forms between
that of the primitive forests and that of the modern world. The
great Cryptogams of the Carboniferous world--the giant
Club-mosses and their kindred--have been slain by the long period
of cold and drought.
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