314 Tlie American Geologist. November, is9s 
fore the elevation in question of the "Continental" and the 
"Blake" plateaux can be accepted as the cause of the Ice age. 
Some of them may be worth stating. 
I St. An elevation of 12,000 feet over any large area is 
known only in Thibet, where the great Desert of Gobi or 
Shamo constitutes the wildest, windiest and snowiest region 
outside of the arctic circle. 
2d. Assuming as a fair rate of elevation three feet in a 
century we should require 400,000 years for the uplifting of 
the "Blake" plateaux above the Atlantic level, so th"t the 
time since the Ice age reached its maximum would on this 
theory exceed even the long limit assigned by Croll. 
3d. In order to allow the occurrence of interglacial 
periods we must assume not a continuous but an intermit- 
tent elevation with alternations of subsidence, allowing amel- 
ioration of the climate. Moreover, if the elevation was the 
main cause of the refrigeration these subsidences must have 
ensued to an extent sufficient to cause this amelioration. We 
shall therefore be compelled to postulate in this case not one, 
but several oscillations, almost or altogether to the full extent 
given above, a result which will multiply the length of the 
glacial period several times and render the discord still great- 
er than in the case of the theory of Croll. 
4th. It will be necessary to find similar conditions in 
other regions in order to explain their glaciation. Not the 
basin of the north Atlantic alone but almost every other part 
of the temperate zones and even the mountainous regions 
within the tropics have been witnesses of a great extension of 
their present glacial systems. It is not easy to require eleva- 
tion over all these places at once or even consecutively. Nor 
is it any easier to conceive how the results of elevation else- 
where could extend over districts so remote. The diversion 
of the gulf stream by the Antillean uplift might chill the north 
Atlantic but could scarcely afifect the Kiwu Sivvu of the 
Pacific or change the climate of Patagonia or of New Zealand. 
If the crust of the earth has been so uplifted and depressed in 
all these regions as to cause the Ice age the Pliocene and Pleis- 
tocene eras must have been a time of instability exceeding 
what now comes within geologi cal experience.^ 
*Note: See for further details on this subject a paper by the 
writer on "Eccentricity versus the Facts" in the Trans, of the Edin- 
burgh Geological Society for 1891, and also "Glacial Notes from the 
Planet Mars" in the American Geologist for 1895. Vol. 16, p. 91. 
