338 SURFACE GEOLOGY. 
mountains ; the débris which it contained forms the upper till; the 
kames show themselves, deposited between walls of ice ; and the valleys 
are filled with plains of modified drift, including the blue and gray clays. 
5. The terraces are produced by excavations of the last formed de- 
posits; vegetation and animal life return; the horse and wild boar, whose 
remains have been found with us, flourished. 
6. A warmer period followed, as illustrated by the presence of the 
rhododendron, cedar, and other plants upon the land; the quahog and 
oyster in the ocean, and the introduction of the American aborigines. 
7. A somewhat colder climate, only a few hundted years back from 
the present date, ensued; New Hampshire was colonized by Europeans; 
and the present type of civilization has abolished the forest and exter- 
minated the larger forms of animal life. 
NoTEs ON THE SuRFACE GEOLOGY oF Coés County. 
By J. H. Hunrincron. 
Fluvial Deposits. These frequently have the appearances, as far as outline is 
concerned, of ordinary river terraces; but an examination of the material of which 
they are composed shows that they have an entirely different origin. In these the ma- 
terial is very coarse ; and we often find boulders 8 or ro inches in diameter. Usually 
they are not very extensive, and they are found only at the mouths of very rapid 
streams. The most extensive deposit of this is in Pittsburg, near the mouth of the 
stream which is the outlet of Back lake. Was all this coarse material, which occupies 
an area of many acres, brought down by the present stream? Mr. David Blanchard, 
who is well acquainted with the outline of the country, thinks that Perry stream once 
had its outlet here. The theory is very plausible, and there is little doubt but that such 
was the case. The barrier of rocks where the road crosses this stream, when it was a 
' few feet higher than it is now, would have turned Perry stream into Back lake; thence 
it would have followed the course of the present outlet of that lake. Most of the drift 
that has been brought down by Indian and Hall’s streams is of the same coarse mate- 
rial. Another deposit of this character is in the town of Stark along Nash stream. 
Almost every stream that comes down from high lands or mountains has brought down 
immense quantities of this kind of material, but nowhere to the extent that has been 
done in the localities just mentioned. How was this deposit formed? The present 
amount of water could not, even at times of the highest floods, have brought down this 
material and deposited it as we now find it. The resource to which we are led to explain 
this phenomena is this: At the time of the final retreat of the glaciers, just before they 
disappeared entirely, they were confined to the deep ravines of the high lands and the 
mountains. The melting of the glacier and the snow, with copious rains, for the moist- 
