494 tots Ne asta Notice. 
surface of this inland sea, and dropped upon the fine and stratified 
es that covered its bottom. 
« Tt is also evident that during the ice-period the northern portion 
of our continent was considerably elevated, as the channels of all the 
draining streams were then deeply excavated (to be one se 
rtially fil'ed with sand, gravel, &c.), and are now trave 
streams which in some instances are flowing 100 or 200 feet ped 
their ancient beds. During this interval the. deeply eroded trough 
of the Hudson, the ines of the Mississippi, the mouth of the 
RUM: and the en Gate must have been excavated. 
is elevation was perhaps sufficient cause for the increase of 
eid for it was doubtless attended by a great expansion of our 
continental surface toward the north, which would be a further 
of The dr portion would serve as a condenser, 
ate with the temperature below 32°, would arrest and accumulate 
the precipitation voa now forms the great streams which drain 
to northern half of o tinent. 
“ The period of the paor of the ice was one of depression, as 
on the Atlantic coast it was followed by the deposition of Drift clays, 
which reach high above the present ocean level. This depression was 
perhaps in itself sufficient to restore the climate to its previous 
standar 
“The few fossils found in the Drift deposits of = interior of De 
continent are the remains of coniferous trees of species which n 
live throughout its northern portions (balsam, i red va White 
pine, &c.), while on the Atlantic coast the Drift clays contain large 
numbers of marine mollusks; and these, as might have ear expected, 
are e or subarctic in character. 
s to the effect produced by the cold period upon animal and 
tels life, it would seem probable that many of the larger verte- 
brates which lived on our continent during the Pliocene age were 
pie of ihe cold period was us limited to those portions of the conti- 
nent lying north of the 38th parallel. That the p-e-existent flora 
and fauna were driven southward, and suffered a narrowing of their 
range, is unquestionable; and this was perhaps fatal to the larges: 
of our land animals ; but it had little effect on the flora and mollus- 
eous fauna, which are found to be essenti ially the same that they 
were before the Glacial epoch. 
* On the whole the effect of the M nd was highly beneficial 
to the portions of our continent most affected by it, as all the aspe- 
rities of the surface were ground down and diminished, while the 
CURE ROPA E UNIS rcgi 
