204 



BULLETIN OF THE 



Across the deep, narrow valley of a tributary to the Kennebec, above 

 half a mile in an air-line northeast from the granite knob before men- 

 tioned, and at the northern limit of the city proper, rises more than 300 

 feet above the river what was formerly known as the Andros Hill, the 

 upper part of the so-called Cushnoc Heights. On the southeastern slope 

 of its upper hundred feet, on nearly the same level with the road, but on 

 the opposite side of that part of the hill, and so hidden from the view 

 of the passer-by, is an abandoned quarry of mica schist. Here, too, the 

 rock plunges off on the south, east, and west beneath an unknown depth 

 of drift.* 



Finally, should the observer examine, for the four miles that intervene 

 between Andros Hill and the northern line of the township of Augusta, 

 the very few exposures of rock in place that occur along the river road 

 on the west side of the Kennebec, and upon the farms crossed by the 

 road, he would find in every case schist, and that only. Upon the cor- 

 responding road cast of the river, only schist is found for the whole six 

 miles of its length across the township. It is evident, then, that the 

 underlying rock of Augusta is the upturned schist, which becomes at 

 Waterville, eighteen miles north of Augusta, the almost vertically placed 

 Taconic or Lower Silurian slate that stretches to Moosehcad Lake on 

 the north, and easterly to and beyond the city of St. John, N. B. 



In the great denudation which tliis extensive region has undergone, 

 the more resisting granites f of Kennebec County have been left project- 

 ing as hills above the softer schists, which, worn down to lower levels, 

 have been covered with deposits of drift, frequently of great thickness. 

 For miles these lower grounds and the hills also may be traversed with- 

 out meeting any indication of the nature of the underlying rock. Thus, 

 upon the road along the western side of the Kennebec, between Andros 



* Half a mile above the bridge, at tbe foot of Cushnoc Heights, is the Kennebec 

 Dam. In 1839 a freshet swept away seven acres of "land at the west end of the dam, 

 and cut a new channel for the river 500 feet in width, the floor of which, when the 

 waters abated, was found to be a transverse ridge of well-marked mica schist. In 

 extending the dam across the new channel, the rock thus laid bare was soon after 



hidden again from view. 



t The so-called granite of Hallowell and Augusta was termed by Jackson " granite 

 gneiss" (B"'irst Rep. Geol. of Maine, p. 83), and is declared by Dr. T. Sterry Hunt to 

 be " true gneiss " {Am. Jour. Sci., [3.] T. p. 85). But is the sudden transition, in so 

 many places within a small area, from crystalline rock to distinct schists, compatible 

 with ti.e idea that the former is a metamorphosed portion of the latter ? Are not the 

 relations of the two more consistent witli the hypothesis that the "gneiss " is in real- 

 ity eruptive granite, which in its paasage through the strata has changed the original 

 slates into hardened schists ? 



