232 STRATIGRAPHICAL GEOLOGY. 



therefore be subsequent to that of the gneiss, and probably synchronous 

 with the period of upheaval of the range. As before remarked, its min- 

 eral character suggests the Chocorua granite. No similar rock has yet 

 been discovered from any part of this range. The rocks on the western 

 slope are largely covered by drift, so that areas much larger than this 

 near Cuttingsville might exist and not be known. 



A heliotype of Mt. Chocorua, taken from the hill about a mile east of 

 Tamworth Iron Works, has been colored to show the situation of the 

 several rocks in the field of view. The details in regard to the rocks 

 have been given upon pages 153 and 154. The pinnacle and south-east 

 spur are composed of Chocorua granite; the eastern ridge, of Albany 

 granite; the lower part of the right flank, of Conway granite. The fore- 

 ground belongs to the Atlantic series of gneisses. Certain parts of the 

 mountain area are left uncolored, as we have not the necessary data to 

 represent them. 



ANDALUSITE SLATES. 



Clay slates, or argillo-mica schists carrying andalusite occasionally, 

 and clayey sandstones constitute the bulk of this formation, attaining, 

 perhaps, a thickness of 1200 feet, supposing the strata to be folded once. 

 The two principal areas of these slates have been described upon pages 

 116 and 175, the first at its crossing by the Mt, Washington carriage- 

 road, and the second under the name of the Mt. Willey range. The third 

 area consists of two small patches on the north and south sides of Mt, 

 Pequawket. It is probable that these three areas were once joined to- 

 gether, the first two effecting a junction near the third, the line of strike 

 having a V shape. A glance at their present wide separation from each 

 other, as portrayed upon the map, will illustrate powerfully the magnitude 

 of the di.slocations and extent of denudation to which the rocks of New 

 Hampshire have been subjected. 



The mineral character of the variety of this rock carrying andalusite 

 is shown by the analysis of G. W. Hawes, herewith presented. Allusion 

 has been made to it upon page 179. 



New Haven, Conn., Aug. 24, 1875, 

 Prof. C. H. Hitchcock : 



Dear Sir — Inclosed you will find the analysis of the slate, which you requested. 



Calculations from the analysis, confirmed by microscopic observations upon a thin 



