238 SURFACE GEOLOGY. 
southward. I have seen no evidence thus far of these northern glaciers extending be- 
yond the range of hills which separates the Ammonoosuc river from the Connecticut 
river valley west of Lancaster, nor have I traced the southern glaciers beyond Lake 
Winnipiseogee. Traces of an eastern glacier moving westward may be seen near the 
Twin Mountain house; but I have not examined that region with sufficient care to give 
minute particulars. 
All these moraines and traces of local glaciers overlie the typical or northern drift, 
so-called, wherever the latter has not been swept away by the local glaciers themselves ; 
thus showing that the great ice sheet was anterior to the local glaciers, and not formed 
by a spreading of preéxisting glaciers. At least, wherever I have recognized traces of 
circumscribed glaciers in regions where they no longer exist, it has always appeared to 
me that the minor areas covered by ice were remnants of a waning sheet of greater ex- 
tent. If the glacial period set in by the enlargement of limited glaciers already formed 
and gradually spreading more and more widely, as Lyell and the geologists of his 
school suppose, the facts which would justify such a view are still to be made known. 
I have not seen a trace of them anywhere. On the contrary, throughout the ranges of 
the Alps, in the Black Forest, the Vosges, as well as in the British islands, in Scot- 
land, Wales, and Ireland, I have everywhere satisfied myself that the more extensive 
the glaciated areas indicated by polished surfaces and moraines, in any given locality, 
the older they are when compared with glacial phenomena circumscribed within nar- 
rower limits. 
It therefore follows from the facts enumerated above, as well as from a general con- 
sideration of the subject, that the local glaciers of the White Mountains are of more 
recent date than the great ice sheet which fashioned the typical drift. On another 
occasion, I hope to show that the action of the local glaciers of the White Mountains 
began to be circumscribed within the areas they covered, after the typical drift had, in 
consequence of the melting of the northern ice sheet, been laid bare in the Middle 
states, in Massachusetts and Connecticut, after even the southern portions of Vermont, 
New Hampshire, and Maine had been freed, and when the White Mountains, the Adi- 
rondacks, and the Katahdin range were the only ice clad peaks in this part of the con- 
tinent. 
When in their turn the glaciers of the White Mountain region began to melt away, 
the freshets occasioned by the sudden large accumulation of water remodelled many of 
these moraines, and carried off the minute materials they contained to deposit them 
lower down in the shape of river terraces. I have recently satisfied myself, by a care- 
ful examination, that all the river terraces of the Connecticut river valley and its tribu- 
taries, as well as those of the Merrimack and its tributaries, are deposits formed by the 
floods descending from the melting glaciers. What President Hitchcock has described 
as sea-beaches and ocean bottoms near the White Mountain and Franconia Notches, 
as well as in the Connecticut river valley and along the Merrimack, have all the same 
origin. The ocean never was in contact with these deposits, which nowhere contain 
any trace of marine organic remains.—American Naturalist, vol. iv, p. 550. 
