226 STRATIGRAPHICAL GEOLOGY. 



tween the porphyry and slate sufficient to authorize the investigation of 

 the question of their identity. As one stands upon Mt. Willey, at the 

 upturned end of the slates (see p. 176), and looks southerly for its con- 

 tinuation, he would naturally fix upon Mt. Nancy as the place for it to 

 appear. Observation proves Mt. Nancy to be composed of the Conway 

 granite (p. 183), but the porphyry covers it to the south, with a slope 

 towards Carrigain; and this might possibly rej^resent the slate in an 

 altered condition. The statement made recently respecting the nearness 

 of the porphyry on Mt. Flume to the crystalline Albany granite, as com- 

 pared with Mt. Willard, is worthy of remembrance in this connection. 



The essential part of our information concerning the Carrigain area of 

 porphyry is given in the description of Fig. 15, a section from Tin to 

 Hancock mountain (p. 147). The view of the Notch (vol. i, p. 596) ex- 

 hibits finely the south side of Mt. Lowell, with the precipice along the 

 middle, and three small slides. Mts. Anderson and Nancy appear imme- 

 diately behind. Between Carrigain notch and Carrigain is a conical peak 

 about six hundred feet below the former, and nearly of the same height 

 with Mt. Lowell. It is one of the porphyritic mountains, and is well 

 shown in the panoramic view from Mt. Tremont in the atlas. No. 58 of 

 Section VIII is a grayish porphyry, from an interesting dyke six feet 

 wide cutting porphyritic gneiss, at the mouth of Carrigain brook. (See 

 p. 103.) 



4. Porphyry in Albany and Waterville. 



The first and most important of these areas has been described upon 

 pages 148-150, in connection with a breccia of possible later origin. 

 Upon Little Deer brook there are outcrops of the red compact feldspar, 

 and a breccia chiefly composed of divers-colored porphyries, including 

 labradorite, quartz, and gneiss. This may possibly be the same with the 

 Mt. Mote and Mt. Pequawket breccias, which are largely composed of 

 andalusite slate, though with a feldspathic paste. 



In Waterville there is a breccia of limited extent, adjacent to labrado- 

 rite rock upon the head waters of Sabba Day brook. And along Mad 

 river, in the vicinity of Greeley's hotel, and for two or three miles above, 

 there are numerous large boulders of red and purple compact and brec- 

 ciated feldspars, which I have thought may have been derived either from 



