ae 
. “ta of af io ; . <1 P 3 " " m Pc : ‘3 . x A ss 
y a7. ¢® Erratic P henometta about Lake a . OF 
* 
Ips. The climatié circumstances capable of accu ting such, 
arge masses of ice around the north pole; having, no doubt, extend- 
‘ed their influence over the temperate zone, and probably produced, 
:t high mountain chains, as the Alps, the Pyrenees, the Black 
Forest, and the Vosges, such accumulations of snow and ice, as 
ri ay have produced the erratic phenomena of those districts. But 
7? coms changes must have taken place in the appearance of 
le continents over which we trace erratic phenomena, since w 
observe in the Old World, as well as in North America, extensive 
«Stratified deposits containing fossils which rest upon the erratics ; 
and as we have all possible good reasons and satisfagtory evidence 
. . for admitting that the erratics were transported ye: agency of 
terrestrial glaciers, and that therefore the tractsof lgnd over which 
"ae they occur, stood at that time above th¢ level of the sea, we are 
: led to the conclusion that these continents have subsided since that 
period below the level of the sea, and that over their inundated 
portions animal life has spread, Anais of organized beings have 
been accumulated, which are mw found in a fossil state in the 
“deposits formed under those sheets of water. 
uch deposits occur at various levels in different parts of North 
America. They have been noticed about Montreal, on the shores 
of Lake Champlain, in Maine and also in Sweden and Russia ; 
and, what is most important, they are not everywhere at the 
Same absolute level above the surface of the ocean, showing that 
both the subsidence, and the subsequent upheaval which has 
again brought them above the level of the sea, have been unequal ; 
and that we should therefore be very cautious in our inferences 
respecting both the continental circumstances under which the 
ancient glaciers were formed, and also the extent of the sea after- 
ward, as compared with its present limits. 
The contrast between the unstratified drift and the subsequently 
Stratified deposits is so great, that they rest everywhere uncon- 
formably upon each other, showing distinctly the difference of the 
agency under which they were accumulated. This -unconform- 
able superposition of marine drift upon glacial drift is also beau- 
tifully shown at the above mentioned locality near Cambridge. 
(See Diagram.) In this case the action of tides in the accumu- 
lation of the stratified materials is plainly seen. 
The various heights at which these stratified deposits occur, 
above the level of the sea, show plainly, that since their accumu- 
lation, the main land has been lifted above the ocean at different 
fates in different parts of the country ; and it would be a most im- 
portant investigation to have their absolute level, in order more fully 
to ascertain the last changes which our continents have undergone. 
rém the above mentioned facts, it must be at once obvious 
that the various kinds of loose materials, all over the northern 
Stoonp Szres, Vol. X, No. 28.—July, 1850. 13 
ae 
pe, Asia and America was of the’same age as the efyatics of the - 
