GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 1 89 



bedding; and in some cases with sucli satisfactory clearness as to prove the true strike 

 of the beds to be N. E. and S. W., and the dip to be for the most part vertical, but 

 with some local arching. Observations made both at this locality and elsewhere, in- 

 duced us to regard the rocks of the Gorge generally as a group of highly metamorphic 

 sandstones and slates, traversed by enormous beds and veins of syenitic granite, by 

 the heating agency of which they had for the most part been rendered semi-crystalline, 

 and in some cases had even been transformed into apparent gneiss and granite. At 

 certain points in these altered strata, the original sedimentary structure is still dis- 

 tinctly retained ; and at one locality we were so successful as to discover well charac- 

 terized impressions and fragments of fossils, from which we have been able, safely as 

 we think, to approximate to the geological age of the strata, as well as to the epoch of 

 the earliest movement of elevation. 



At the curve in the valley, where the anticlinal axis xy crosses the Gorge obliquely, 

 entering the end of the ridge already alluded to, and from that point down to the Wil- 

 ley house, the rocky fragments dislodged from the naked and steep sloj^es on either 

 side, consist chiefly of a finely laminated hard sandy slate of a bluish color, and a 

 coarse very compact rock of similar composition ; and mingled with these are occa- 

 sionally found masses of the same composition, but wearing a more altered aspect, 

 some of them containing crystalline spots and white amygdaloidal kernels, the obvious 

 indications of an advanced stage of igneous metamorphosis. These fragments are 

 extremely instructive ; for they exhibit nearly all the later stages of alteration, from 

 the ordinary sedimentary texture to the diffusedly crystalline one. In some cases we 

 see the planes or lines of sedimentary deposition coexisting with a general but not 

 fully perfected crystallization, in which however may be distinctly discovered genuine 

 feldspar, augite and 7nica. Such specimens are to be viewed as an incipient horn- 

 blendic gneiss, in which through the sedimentary granular structure, typical of the 

 secondary strata, may be seen everywhere and intimately dispersed, the crystallized 

 definite mineral aggregates equally typical of the so-called primary rocks. Many of 

 these specimens seen facewise, would pass for genuine ancient gneiss ; but looked at 

 edgewise, they betray equally unequivocal marks of their sandstone nature and origin. 

 Among the more argillaceous altered rocks, are some which have evidently once been 

 sandy shales, but which now consist of a purplish gray semi-crystalline base, imbed- 

 ding several obscurely developed minerals. These rocks likewise contain serpentine, 

 talc, and other silico-magnesian species, as well as some clearly insulated grains of 

 crystalline quartz. 



About one third of a mile below the northern entrance of the Notch, on the west 

 side of the Gorge and therefore not far from the extremely wild and picturesque cas- 

 cade called the Flume, there occurs especially in the craggy summit of the mountain, 

 a thick-bedded white semi-crystalline altered sandstone, which is intersected by injec- 

 tions of feldspathic granite, and is itself in many parts concreted into a near approxi- 

 mation to a binary granite composed of distinctly developed cjuartz and white feldspar, 

 with a few sparsely scattered specks of mica. In its weathered surfaces this rock 



