126 STRATIGRAPIIICAL GEOLOGY. 



this branch with the main river. Massive Kght-colored traps appear 

 here. At the fork the strata of porphyritic aspect dip only 20° a Httle 

 west of north; and fragments of other varieties of gneiss are imbedded 

 in them. A few rods above the confluence of the two streams the dip 

 is N. 6f E. 



The occurrence of the labradorite rock is described elsewhere. The 

 first rocks seen below it dip thirty or forty degrees northerly, and they 

 are the dark-colored, twisted andalusite mica schists, with little feldspar. 

 Below the outlet of the brook from Clinton the strata become flinty, are 

 quartzites, with the characteristic White Mountain mica scattered through 

 them, and are inclined 45° N. 43° W. A remarkable trappean conglom- 

 erate is next met with. For one hundred feet on the east branch there 

 is an interesting trappean conglomerate, with pebbles of various Mont- 

 alban schists, some of them three feet in length. Seams of an argilla- 

 ceous cement interpenetrate them. At the lower end of the mass the 

 quartzose rock reappears, dipping easterly. Across the river a similar 

 ledge crops out, having a striped appearance, dipping 30° N. 38° W., or 

 directly under the preceding. Where the valley curves sharply to the 

 east, the hard quartzite has been cut deeply by the river, which has 

 shrunk to less than half its former dimensions. At a great bend below, 

 an enormous amount of drift is exposed high up on the southern bank. 

 At this point the ledges of granite commence, though enormous boulders 

 of them are strewn by the river's side for half a mile above. This 

 granite is related to the "Conway" variety. 



A matter of much interest may be seen below. After following a dis- 

 tinct granite floor for a considerable distance, — the whole gulf having 

 this rock upon both walls a thousand feet high, — there appears an island 

 of the flinty rock, which may be the remnant of the underlying material 

 once covered by the joasty granite, and exposed at the present time on 

 account of the long-continued agency of the water passing over it. The 

 same rock crops out again at Bemis station, about three miles lower 

 down. These and other facts lead us to believe that the base of the 

 Saco valley lies very near the base of the whole series of Pemigewasset 

 granites. 



There is an interesting scries of falls on this river, five or six miles 

 above its junction with the Saco. Mr. Huntington says that the upper 



