regions.

In fig. 5, scarcely any of the land extends from the equator towards the
poles beyond the 30th parallel of latitude; and fig. 6, a very small
proportion of it extends from the poles towards the Equator beyond the
40th parallel of latitude.

_Position of land and sea which might give rise to the extreme of
heat._--Let us now turn from the contemplation of the winter of the
"great year," and consider the opposite train of circumstances which
would bring on the spring and summer. To imagine all the lands to be
collected together in equatorial latitudes, and a few promontories only
to project beyond the thirtieth parallel, as represented in the annexed
maps (figs. 5 and 6), would be undoubtedly to suppose an extreme result
of geological change. But if we consider a mere approximation to such a
state of things, it would be sufficient to cause a general elevation of
temperature. Nor can it be regarded as a visionary idea, that amidst the
revolutions of the earth's surface, the quantity of land should, at
certain periods, have been simultaneously lessened in the vicinity of
both the poles, and increased within the tropics. We must recollect that
even now it is necessary to ascend to the height of fifteen thousand
feet in the Andes under the line, and in the Himalaya mountains, which
are without the tropic, to seventeen thousand feet, before we reach the
limit of perpetual snow. On the northern slope, indeed, of the Himalaya
range, where the heat radiated from a great continent moderates the
cold, there are meadows and cultivated land at an elevation equal to the
height of Mont Blanc.[194] If then there were no arctic lands to chill
the atmosphere, and freeze the sea, and if the loftiest chains were near
the line, it seems reasonable to imagine that the highest mountains
might be clothed with a rich vegetation to their summits, and that
nearly all signs of frost would disappear from the earth.

When the absorption of the solar rays was in no region impeded, even in
winter, by a coat of snow, the mean heat of the earth's crust would
augment to considerable depths, and springs, which we know to be in
general an index of the mean temperature of the climate, would be warmer
in all latitudes. The waters of lakes, therefore, and rivers, would be
much hotter in winter, and would be never chilled in summer by melted
snow and ice. A remarkable uniformity of climate would prevail amid the
archipelagoes of the temperate and p