l66 STRATIGRAPHICAL GEOLOGY. 



Saco valley with more precision than usual. At the end of the road on 

 the summit the rock is the Conway granite, with joints running in vari- 

 ous directions. To the east, the line of junction between the granite and 

 hard gneisses may be observed about five or six hundred feet distant, at 

 the south-east angle of the cliff. On passing to the base of the first cliff, 

 one can readily distinguish this line of junction, with a north-west course,, 

 and vertical. On looking down the steep, impassable slope, the schists 

 seem to come to a point in the granite one or two hundred feet distant. 

 In the granite above there are joints parallel with the line of union, 

 seen especially where the cliff overhangs about twenty feet. The most 

 northern point where I have seen the granite must be about six hundred 

 feet north from the summit, near the line cut from the carriage-road 

 to the new flume. To the west, perhaps two or three hundred feet of 

 surface is occupied by the Conway variety. The principal part of the 

 cliff is composed of this rock, and it may be followed down across the 

 railroad to the upper bridge over the Saco, in the carriage-road down 

 the Notch. The railroad runs over this rock about seventy rods. The 

 vertical thickness, from the Saco to the top of Mt. Willard, is at least 

 1800 feet, which represents the vertical dimensions of the granite. It 

 is supposed to be continuous southward along the west base of Mt. 

 Webster, Along the railroad it disappears, passing beneath the spotted 

 granite and the slates, coming up about a quarter of a mile south of 

 Willey brook, as if it constituted a synclinal axis. 



Alo7ig the Railroad. Starting from the Crawford House station, we 

 proceed 1900 feet before coming to the first cut in the rock, 200 feet 

 long. This interval represents an extensive accumulation of detritus 

 brought down from the adjacent mountains by the Ammonoosuc branch, 

 Cascade brook, Gibbs brook, and others of smaller size. The ledges we 

 suppose fall off to the north very much as they do towards the Willey 

 house, and would therefore be more than one hundred feet below the 

 Crawford house. On the north side of Elephant's Head is a ledge of 

 gneiss resembling the Concord granite, with jointed planes, possibly 

 strata, dipping N. 87° W. The stone has been quarried somewhat for 

 piers and abutments. The rock in the first cut lies beyond this granite, 

 and is a hard gneiss, breaking with difflculty into angular pieces, with the 

 dip of S. 63" W. 75°, It is cut by several large and coarse granitic veins, 



