l60 STRATIGRAPHICAL GEOLOGY. 



the porphyritic gneiss, disposed in nearly horizontal plates, near Walker's 

 falls, has been noted upon page loi. We have got glimpses, besides, of 

 Montalban schists, the Franconia breccia, and labradorite rocks along this 

 same range or uplift of older rocks, between the valley granites and those 

 high up the flank of the Lafayette range. The finer Conway granite, like 

 that of Mt. Profile, crops out on the bridle-path up Lafayette, midway 

 between the south Franconia line and the Lakes of the Clouds. 



Between Mts. Lafayette and Haystack there are three elevations, whose 

 character may be conveniently mentioned here. Lafayette itself is com- 

 posed of porphyry at the very summit. The long north-westerly spur 

 from it has the same character. The first eminence towards Haystack 

 is composed of gneiss connected v/ith the Franconia breccia. Specimens 

 of granular quartz illustrate the second. The third is composed of Beth- 

 lehem gneiss. Haystack itself seems to belong to the Albany granite 

 layer. Specimens from these summits were collected for us by Messrs. 

 Smith, Hoitt, and Conant, of the Dartmouth party of 1871; and the trips 

 taken to find them were very laborious. It is supposed that the Albany 

 granite is continuous from Haystack to the north slope of Twin moun- 

 tains, but this theory has not been verified by actual perambulation. 



Mr. Huntington having climbed Mt. Lafayette since the above was 

 put in type, communicates his impressions of what he saw, in the follow- 

 mg letter: 



The first outcrop of rock on the bridle-path above Eagle Cliff is perhaps three fourths 

 of the distance from the Cliff to the summit of the ridge west of the Lake of the Clouds. 

 It is a narrow band of the spotted (Albany?) granite. On the summit of the ridge the 

 rock is porphyritic gneiss, the dip of which is probably south 60°. Whether it is the 

 same as the gneiss in the central part of the state is a question, since you will remem- 

 ber that portions of the rock that makes up the breccia are also porphyritic. Just 

 above the Lake of the Clouds there are a very few crystals of feldspar ; and the rock 

 resembles that of a portion of the breccia. Above the rock is a breccia, or, if it is a 

 gneiss, there are concretions in it. There is little doubt that it is a breccia, however. 

 The rock succeeding this looks more like a gneiss, and dips almost directly east. We 

 then have a fine- and coarse-grained granite, then the spotted (Albany .'') granite, and, 

 last, the porphyrite, that forms the summit of the mountain. On the lowest part of 

 the ridge, towards the south peak, the spotted granite outcrops; but on all the liigher 

 points, including south peak, the rock is porphyrite. I did not see any rock that I 

 could call labradorite, though even in the spotted granite some of the crystals of feld- 

 spar appear to be labradorite. 



