Glacial Theories — Cosmical and Terrestrial. — Clay pole. 313 
tions as no other has ever done, there is yet a consciousness 
that its base is slipping away and that the superstrnctnre is 
unstable. 
As a resuh attention has been again directed to strictly 
terrestrial conditions, and the newest results of investigation 
have been employed in order to find, if possible, sufficient 
cause for so intense a period of refrigeration in latitudes so 
low. The contour lines of the Atlantic have been quoted to 
prove that ancient continental shores exist at two levels, which 
have been named respectively the "Continental" and the 
"Blake" plateaux. To bring both these above the sea-level 
at present would need an elevation of ten or twelve thousand 
feet to the south and much less to the north. So great a 
change of level, if real, must have been attended with momen- 
tous results, both in the drainage and the temperature, and 
the investigation of these details is the most recent line of re- 
search in glacial geology. Beyond all question it is quite pos- 
sible to picture a state of things much resembling the Ice age 
with the data thus supplied. The diversion of the gulf stream 
or its reduction in temperature would certainly chill the north 
Atlantic and the British Isles and might even so far reduce 
the temperature as to cause a precipitation in the winter which 
the summer might be unable to melt, thus producing an ac- 
tual Ice age. Add the refrigeration due to the postulated ele- 
vation of the temperate coast of the north Atlantic to that due 
to diversion of the warm current, and the two may well be 
allowed to have produced more momentous climatic changes, 
perhaps even all the phenomena of the Ice age in western 
Europe and eastern North America. 
The importance of this contribution to the literature of 
the subject can scarcely be over-estimated. It suggests a 
possible cause for at least a part of this mysterious episode in 
the history of our earth. But it is very far from complete- 
ness and equally far from meeting all the conditions of the 
problem. We may fully admit that vast elevations and de- 
pressions of parts of the surface have taken place without 
being compelled to admit the elevation of the West Indies to 
the extent of 12,000 feet. But to deny its possibility would be 
equally illogical. There are numerous side-issues needing 
consideration and many minor problems awaiting solution be- 
