146 STRATIGKAPIIICAL GEOLOGY. 



and near the north hne of Elkins's Grant, the usual variety of this for- 

 mation is present. Two miles above these falls, on the stream two miles 

 south, on a tributary, and on another branch in going from Mt. Carrigain 

 to Willey, the granite is made of finer materials than ordinary, and there 

 is much quartz present. The same is true of the rock at Nancy pond. 



The mountains between Mts. Willey and Nancy are comparatively low, 

 falling off more than a thousand feet. This is probably due to a line of 

 subsidence, since the finer-grained granites and sienites occurring there 

 are among those usually capping the more elevated summits. We have 

 on hand a number of facts concerning the granites on both sides of the 

 Saco river, which will be presented further along, as some of them will 

 be amplified or otherwise modified by a special reexamination of the 

 valley, made in 1875. 



Section from Tin to Hancock mountain. The figures for the altitudes 

 of this route are mentioned in the chapter on Altitudes, page 290 of Vol- 

 ume I. Upon Tin mountain the schists belong to the Montalban series, 

 with a high inclination somewhat west of north. Between the tin mine 

 and the village of Jackson there is a development of Albany granite. On 

 reaching the lowest point on the section, at Jackson falls, the rock has 

 changed to the Conway granite. In the bed of Ellis river there are joints 

 dipping at an angle of seventy or eighty degrees to the west, which are 

 so well marked as to resemble bedding. Others are present, also, as ap- 

 pears from an inspection of the heliotype in Volume I, opposite page 

 256. A mile or so lower down are Goodrich falls, represented in the 

 hehotype very finely. Mr. Vose remarks of the rock here: "The joint- 

 ing and quasi-bedding of the granite is very well seen from above the 

 bridge to below the falls. One set of joints runs east and west, and dips 

 steep to the north. The other set runs S. 33° W. The granite at this 

 place decomposes in a remarkable and instructive manner, showing the 

 original structure of the rock better by the decay than by the solid 

 ledge." [See Fig. 14.] Returning to the precise line of section, we 

 find the same rock extending far up the flanks of Cobb's hill. The sum- 

 mit of this low elevation is composed of the Albany granite. On the 

 west side the Conway rock returns again, and extends to the valley of 

 Rocky branch in Bartlett, where there is an outcrop of the Montalban 

 schists overlooked by us in our enumeration of the several areas occu- 



