GLACIAL DRIFT. 339 



ure-laden currents coming in contact with these fields of ice would have been suddenly 

 condensed, — all these would have had a tendency to produce floods that are now un- 

 known. 



Karnes. The best examples of kames seen in Coos county are those which were 

 formed as the glacier retreated from the valley of the Connecticut, in Columbia and 

 Colebrook, and nowhere are they more striking than at Colebrook village. These are 

 interesting, from the fact they show that for years the great glacier that filled the valley 

 of the Connecticut here had its terminus. The fact that these gravel ridges do not ap- 

 pear above Colebrook shows that the change of climate was such as to cause the glacier 

 to disappear rapidly when it receded above that point. The expansion of the valley 

 at the village and just above, and its contracted limits below, were also causes that may 

 have produced this phenomenon. 



Erratics. There are very few but that have noticed, scattered through the fields, 

 boulders unlike those of the rocks in the immediate vicinity. These boulders we call 

 erratics or wanderers, because they have come from some distant place. Throughout 

 northern New Hampshire, on account of the extensive tracts of forests, the study of all 

 phenomena of drift is pursued under the most unfavorable circumstances, since in the 

 forests there are no excavations, except that done by water along the streams. The 

 boulders as well as the ledges are much more commonly covered with earth, or, at 

 least, they are overgrown with moss, which has to be removed before we can tell 

 anything about the rocks. To study thoroughly the geography of a country covered 

 with forests, would, under most circumstances, be an endless task, although the area 

 might be quite limited. On account of the fragile nature of many of the rocks in the 

 extreme northern part of the state, boulders are not so numerous as in some other 

 sections ; and the absence of granite boulders is especially noticeable. North of Con- 

 necticut lake I do not remember to have seen but one granite boulder in all that 

 area, and that was three or four miles east of Third lake. On Indian stream, eight or 

 ten miles from its mouth, there were several boulders of conglomerate, and just north, 

 three of brecciated iron ore. In Colebrook, near Mr. L. Dinsmore's, there is a con- 

 glomerate which is quite attractive even in hand specimens. None of these just men- 

 tioned were found in place, and where they came from is a matter of conjecture ; but 

 it is altogether probable that they came from Quebec province. Most of the boulders 

 found in New Hampshire as far south as Columbia are derived from the hard bands in 

 the argillaceous schist, or they come from the band of hornblende rock extending from 

 Colebrook to the boundary. Everywhere south-east of this band, as far as Maine and 

 even beyond the Magalloway, boulders of this rock are seen. As the rock is unlike 

 any other, they are noticeable wherever they may be found ; and they show that the 

 general direction of the drift was considerably east of south. 



In Stratford, just north of Little Bog brook, there is quite a remarkable collection of 

 granitic boulders, both on account of the number and the limited area where they are 

 found ; besides, they must have come from Vermont, as granitic rocks of this kind are 

 not found in New Hampshire. 



