284 SURFACE GEOLOGY. 
nents average coarser. This hardpan is certainly prior in age to the 
lower till; but that circumstance may not compel us to call it Tertiary. 
If length of time is requisite for the induration of till, this hardpan should 
be much older than the common moraine. There is nothing of signifi- 
cance in the shape of this earth heap. It is not as conspicuous as a 
small lenticular hill. After the access of air to the lower deposit, its 
great induration disappears. When it is well exposed to rain, water 
mixes with it, making a compound that will flow readily down a slope. 
A case similar to this is in Pittsfield, midway between Webster's nal 
and the village. The railroad excavators had the same experiences that 
have been narrated for Lyndeborough. Gov. Prescott informs me that 
similar experiences befell persons endeavoring to excavate the earth for 
a well near his residence in Epping; and recently I found the same 
story told of drift in Amherst, Mass., and Hartford, Conn. The exam- 
ples may multiply, and eventually furnish us the answer to our question 
as to the peculiarities of their origin. 
Drirt in Nortu Conway. 
As an example of the aspect of the difference between the ordinary 
till and the modified drift, I would refer to the accompanying heliotype, 
illustrative of these two deposits in North Conway where the road 
crosses Artists’ Falls brook, near the Macmillan hotel. To render the 
sand more distinct, a faint brown color is employed to show its limits. 
It is about 10 feet thick, forming about one fifth part of the exposure. 
There are boulders in the till here about a yard in diameter. The sand 
of North Conway is usually widespread, but very thin. Quite a large 
mass of it, as long as a small lenticular moraine, occurs just to the south 
of the stream opposite the hotel. This is the position from which the 
fine view of Mt. Pequawket, employed for the frontispiece of Volume I], 
was taken. 
Priant Revics oF THE GLaciaAL Periop. Full descriptions of the Hudson’s Bay and Greenland floras 
now existing in the White Mountains have been presented in Volume I, pp. 392 and 568. No better argument 
to show that an arctic climate once existed in New Hampshire than the presence of these plants, as well as the 
corresponding insects described in the same volume, Chapter XII, can be adduced. They also imply the cor- 
rectness of the glacial instead of the iceberg theory of the drift, and also that the cold conditions spread them- 
selves gradually over the continent, disappearing slowly also. 
