GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 1 73 



tinuoiis from Mt. Willard across the valley to Mt. Webster, through the 

 flume and cascade, at the level of the higher land. At the time of the 

 ejection of the trap, the liquid would have flowed out at the bottom of 

 the valley and not have reached the summits of the mountains, unless 

 the whole space between were filled up to the brim ; therefore the ledge 

 must have been continuous from summit to summit. It would seem to 

 follow in like manner, from the occurrence of numerous dykes in Mt. 

 Webster, that the whole of the Notch valley was once filled with solid 

 rock. The immense depth of this remarkable gorge, from the Gate to 

 Sawyer's rock, has all been excavated out of solid material by aqueous 

 and glacial agencies, acting constantly since the beginning of Paleozoic 

 time. Possibly its course may have been determined by fractures induced 

 during the folding of the strata. Essentially this view of the origin of 

 the Notch, especially the use of trap dykes to prove an immense erosion, 

 was suggested by Prof. O. P. Hubbard, in a memoir from which extracts 

 will be presented shortly. 



Below this northern flume there are about 120 feet of hard schists, 

 and then for the rest of the way to the railroad the Breccia granite is 

 exposed in a smooth precipitous slope, almost impassable. Paths could 

 easily be made along this eastern wall of the mountain, that would be 

 very attractive to tourists. If they are slightly dangerous the course 

 will be the more eagerly traversed. 



NortJi-zvcst side of Mt. Webster. A further examination of the north- 

 west side of Mt. Webster has enabled us to profit by our knowledge of 

 the exposures along the railroad. It will be remembered that the Breccia 

 granite starts near the Butterwort flume, and gradually descends the wall 

 of Mt. Willard to the James cut, thence to the outlet of Dismal pool, 

 whence it changes its course and begins to pass up the east side of the 

 valley, crossing Silver cascade a hundred feet east of the road. It con- 

 tinues from thence to the most considerable cliff on the west side of Mt. 

 Webster, figured in our heliotype, p. 79, Vol. I. At this point it has 

 about the altitude of Mt. Willard, and is estimated to be 300 feet thick. 

 As near as I can judge, its course is not in a right line, on account of 

 various shiftings of the rock not fully understood. The general course 

 is from near the top of the Willard cliff to Dismal pool, thence up the 

 west side of Webster to the greatest precipice, and perhaps farther. 



