Geology and Natural History. 315 
the Atlantic: that the heat which is now carried to the north 
a a 
existed we plesk dhe with that of unusual cold over the land— 
conditions, as Professor Verrill states, that would make a storm 
region of ‘tremdtous effects over the ice within 300 or 400 nile 
of the warm sea — All the conditions demanded are hare: 
heo 
Brudes su sur les G'laciers,—a work that made an epoch in geology 
by its demonstrations of the glacier origin of the Drift,—sug- 
gested also that the principal epochs of life-extermination in 
geology were epochs of cold—* que les plus grands froids ont 
mination; and there is reason to believe that he was right as to 
some je eae of the epochs. Th writer es her two such in 
ower Permian may be a mark of the slow approach of such an 
era of cold’”* at the close of Paleozoic time; and the Triassic 
rocks of eastern North America seem to bear, in their large 
cessive precipitation and also the cold of such an epoch — “gg 
yet passed. 
On the Submergence during the Glacial period. Peaks 
Crs in the ne ral tenes — ; uly and August, - pps Lead 
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of the ice of the Glacial period; or, as he has it, s miliergete 
ie A the Glacial period, he holding red the aie Laie by was a 
riod of lower level of the land than eeds on the 
supposition, ge argued for by him, that the aol of ‘the Glacial 
iod was due to the eccentricity of the earth’s orbit, = that it 
ected ih sovthded and southern hemispheres alternate 
The oval of two miles of ice from the Antarctic Continett 
ii displace the center of gravity 190 feet, and the formation of 
a mass of ice of one-half this thickness in the Arctic regions would 
te 
Further, the area of the Antarctic ice-cap being z34¢, of that of the 
Ocean, therefore, allowing 0°92 for the density of ic ice, the melting of 
254 feet of ice from the cap weg: raise the general level of the 
* Manual of Geology, 2d edit., p. 43 
A Base agency of ice oS the Rica of the Trias of Eastern North Am 
has been s suggested by T. A. Conrad, and also by H. Watts, sek iy beh a ek” 
Am. Jour, Sct.—THIrD Senzzs, Vou, IX, No. 52,—ApriL, 1875. 
