GEOLOGY OF THE LAKE DISTRICT. 609 



them rather than the Exeter or Quincy, and they are unUke the Chocorua 

 series. Opinions as to the comparative antiquity of these several eruptive 

 rocks cannot yet be suggested with any probabihty. They occur in the 

 midst of Lake and Montalban gneisses, while the granites have disrupted 

 andalusite slates. 



Green Mountain Area. This is a little over four miles long and two 

 wide in the north part of Effingham. The prevailing rock is a porphy- 

 ritic granite, the feldspar crystals usually not exceeding half an inch in 

 length. I have seen this variety of rock for three miles along the south- 

 ern part of the area. Judging from this circumstance, and from the abun- 

 dance of large blocks dispersed by drift in the neighboring towns, I have 

 concluded the whole mountain might be composed of the same material. 

 I have found the Mt. Bet granite on the north side, at the ice cave. What 

 the material is upon the very summit can be ascertained only by actual 

 visitation. There are no schists cropping out adjacent to the granite on 

 the northern half of the area. A ferruginous mica schist at A. W. Drake's, 

 upon the south side, dips 70° S. 70° E. This makes an anticlinal axis 

 with the nearest ledges to the west, in Ossipee. 



RocKS IN Maine. 



The geology of quite a wide tract in Maine is presented upon our 

 sheets, opposite the three northern topographical districts. No geologist 

 has ever traversed the north-east portion of the northern sheet. It is 

 from the most meagre data that the delineation represented is based. 

 On the Magalloway river, specimens have been obtained of both the 

 Lyman and Lisbon groups of the Huronian. Mt. Eziscoos and the neigh- 

 borhood are genuine granites. There is believed to be a considerable 

 area of the Lake gneiss in Andover and westward. To the south the 

 great bulk of the formations consists of the Montalban series in its vari- 

 ous forms. There is a greater development of this group in Maine than 

 in New Hampshire. 



One of the most interesting areas of igneous materials in Maine is the 

 trachytic rock of Mt. Pleasant, in the towns of Bridgeton and Denmark, 

 This elevation is recognized readily from the mountain summits of New 

 Hampshire, as it is a long mass rising up from an apparent plain. The 

 mass of the mountain is a sienite like that of Tripyramid, with tri- 



VOL. II. T^ 



