232 J.D. Dana on Time-boundaries in Geological History. 
nected with the two grand transitions in the life of the world, 
that of the Paleozoic to the Mesozoic, and that of the Mesozoic 
to the Cenozoic.’ 
Asia probably affords similar facts, The two opposing moun- 
tain chains of most prominence are the Altai on the north, and 
W 
act time of the main part of the elevation, the evidence is not 
yet —— Tt is, however, certain that the western por- 
tion, in which Cashmeer lies, was still 15,000 feet below its pres- 
ent level in the early Hocene; and the elevation, whenever com- 
menced, was completed throughout the chain, like that of the 
Alps an and Appenines, only after the Tertiary period had begun. 
Thus the progress was gradual; and it covered the same part of 
logical time as that of the loftier mountains of America and 
As above remarked, the great transition in the life of 
he glo obe which took place at ‘the close of the Cre etaceous, shows 
that, reer eens this prolonging of the era of elevation, 
there was a crisis in the move ement, climate and otherwise, at the 
close of Mesozoic time. The great physical changes in progress 
then made their profoundest mark on the world’s history. 
In South America, there is proof, as Darwin has shown, that 
the Andes were, to a ‘large gov raised from the ocean after the 
close of the Mesozoic. The elevation was not completed at once, 
any more than that of the ae Mountains or Alps, but con- 
tinued afterwards to increase at intervals, while undergoing 08 
eillations, during the subsequent Tertiary period.’ The Rocky 
ountains and Andes were one, apparently, in time = origin, 
as they are one in position along the American contin 
Is : be then probable, that over ail the sragsesags oe making 
of t -mountains—the chains which give the land its 
dominaik asares, or rather which are its patchncea” 
as in America, with the two grandest epochs in the geolog! 
past, on in other words, gives bounds to Paleozoic a — 
zoic tim: 
in the extensive tii Star o rin el ine : ‘ 
and and elsewhere; so D: Forbes, @ J. Geol Sot. 180, p. 7. 
