Principles of Geology: or, The Modern Changes of the Earth and its Inhabitants Considered as Illustrative of GeologyLyell, Charles, Sir
Science
Principles of Geology: or, The Modern Changes of the Earth and its Inhabitants Considered as Illustrative of Geology
Lyell, Charles, Sir
Geology
Soon after the first publication of this theory of climate, an objection
was made by an anonymous German critic in 1833 that there are no
geological proofs of the prevalence at any former period of a
temperature _lower_ than that now enjoyed; whereas, if the causes above
assigned were the true ones, it might reasonably have been expected that
fossil remains would sometimes indicate colder as well as hotter
climates than those now established.[202] In answer to this objection, I
may suggest, that our present climates are probably far more distant
from the extreme of possible heat than from its opposite extreme of
cold. A glance at the map (fig. 6, p. 111) will show that all the
existing lands might be placed between the 30th parallels of latitude on
each side of the equator, and that even then they would by no means fill
that space. In no other position would they give rise to so high a
temperature. But the present geographical condition of the earth is so
far removed from such a state of things, that the land lying between the
poles and the parallels of 30, is in great excess; so much so that,
instead of being to the sea in the proportion of 1 to 3, which is as
near as possible the average general ratio throughout the globe, it is 9
to 23.[203] Hence it ought not to surprise us if, in our geological
retrospect, embracing perhaps a small part only of a complete cycle of
change in the terrestrial climates, we should happen to discover
everywhere the signs of a higher temperature. The strata hitherto
examined may have originated when the quantity of equatorial land was
always decreasing and the land in regions nearer the poles augmenting in
height and area, until at length it attained its present excess in high
latitudes. There is nothing improbable in supposing that the
geographical revolutions of which we have hitherto obtained proofs had
this general tendency; and in that case the refrigeration must have been
constant, although, for reasons before explained, the rate of cooling
may not have been uniform.
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