l-vegetation shows
a uniformly warm climate from Spitzbergen to Africa. Mr. Drew ("The
Romance of Modern Geology," 1909) says that "nearly all over the globe
the climate was the same--hot, close, moist, muggy" (p. 219).

* An apology is due here in some measure. The work which I
quote as of Professor Chamberlin ("Geology," 1903) is really
by two authors, Professors Chamberlin and Salisbury. I
merely quote Professor Chamberlin for shortness, and because
the particular ideas I refer to are expounded by him in
separate papers. The work is the finest manual in modern
geological literature. I have used it much, in conjunction
with the latest editions of Geikie, Le Conte, and Lupparent,
and such recent manuals as Walther, De Launay, Suess, etc.,
and the geological magazines.

The exception which Professor Chamberlin has in mind when he says "most
of the data" is that we find deposits of salt and gypsum in the Silurian
and Lower Carboniferous, and these seem to point to the evaporation
of lakes in a dry climate. He admits that these indicate, at the most,
local areas or periods of dryness in an overwhelmingly moist and warm
earth. It is thus not disputed that the climate of the earth was, during
a period of at least fifteen million years (from the Cambrian to the
Carboniferous), singularly uniform, genial, and moist. During that vast
period there is no evidence whatever that the earth was divided into
climatic zones, or that the year was divided into seasons. To such an
earth was the prolific life of the Coal-forest adapted.

It is, further, not questioned that the temperature of the earth fell in
the latter part of the Carboniferous age, and that the cold reached
its climax in the Permian. As we turn over the pages of the geological
chronicle, an extraordinary change comes over the vegetation of the
earth. The great Lepidodendra gradually disappear before the close of
the Permian period; the Sigillariae dwindle into a meagre and expiring
race; the giant Horsetails (Calamites) shrink, and betray the adverse
conditions in their thin, impoverished leaves. New, stunted, hardy
trees make their appearance: the Walchia, a tree something like the low
Araucarian conifers in the texture of its wood, and the Voltzia, the
reputed ancestor of the cypresses. Their narrow, stunted leaves suggest
to the imagination the struggle of a handful of pines on a bleak
hill-side. The rich fern-po