23S Tlii'Annricilit (T>'(tln<l'ixi . Oftobt?!', IWlt 
mates, witli aldindnut snowfall but noi cxci'ssivc cold, wlu'iv the 
ice-sheets were aecuiimlated. 
Mr. AV.vRRKN Uph-vm referred to recent calculations by Prof. 
T. (J. IJonney, that a decrease of about fifteen degrees in the 
mean temperature of Kurope and North America might reinstate 
a glacial epoch. For this change, according to ol)servations of 
mean temperature as dependent on altitude, an elevation of 5,000 
feet, or probably even of :i,000 feet, would suffice. Fjords of 
Arctic and northern shores oi all glaciated regions, the continua- 
tion of the Hudson valley to a depth of 2,800 feet below the sea 
level, and equally deep submerged valleys on the coast of Cali- 
fornia, demonstrated by Le Conte to belong to the Pleistocene 
period, show that the unique Ice age was closely attended by a 
verj^ remarkable epirogenic uplifting of this continent. Two so 
wonderful geologic episodes probal)ly sustained causal relations 
to each other, the great elevation being the cause of cool climate 
and ice accumulation. Such geographic changes seem also more 
likeh' to come on rapidl}', to cease bj' ensuing depression, and 
afterward to be renewed, than would seem possible for changes 
of the poles. The present rate of change of the north pole is 
about 450 feet during a hundred A-ears, but the distance that it 
should be removed to produce each glacial epoch of the two or 
more recognized within the Pleistocene period is 1,000 or 1,500 
miles. 
On tltc iiortliiciinl (iiid castiinnl cttensioii of Pre- Pleistocene 
gravels in the basin of the Mississipj}!. B}' R. D. SALISBURY, 
The Lafa^'ette formation is found to extend beneath the glacial 
drift in western Illinois about 100 miles northward from the drift 
l)oundary, to the vicinity of Keokuk, Iowa. Farther to the north, 
at Kock Island, the same formation is known to have existed, for 
peljbles of its gravel occur in the drift. Some of the gravels of 
the driftless area in Wisconsin are probably also of Lafa3'ette age. 
In the Ohio V)asin the Lafayette gravel contributed to the drift as 
far eastward as the southeast corner of Indiana. 
On cirtoin ixtni-iiioniinic ilrift phenomena of Xeir Jirneij. By 
R. D. Salisbi'rv. Deposits of undoubted till have been discov- 
t'red five to twenty miles south of the terminal moraine which 
was mapped about fourteen j'eaj's ago across northern New Jersey, 
and which has since l)een supi)osed to V)e the extreme limit of 
glacial action. The Ijoulders and smaller rock fragments of this 
