116 Prof. J. D. Dana — Metatnorphism of 



grey colour than the graniie ; it is quartzose and garnetiferous, 

 strongl3r raicaceous with black mica, and contains magnetite and 

 a little staurolite. The schist is consequently not a schistose por- 

 tion of the granite, but a distinct bed ; it is like the schist in its 

 minerals, but in its more gneissic character indicates that it is 

 intermediate between the schist and the soda-granite. The eastern 

 face of the same ledge is about a dozen feet to the east of the western, 

 and here the junction of the schist with the granite looks more 

 abrupt, but partly in consequence of erosion ; above this plane 

 of junction, in the mass of the granite, distinct though fainter 

 indications of flexed beds exist. The change above m from soda- 

 granite to quartz-diorite is simply a change in the substitution of 

 hornblende for the larger part of the black mica, the felspars 

 being equally triclinic in the two, and the quartz equally deficient 

 in amount. At a small bluff, 160 yards to the west of m (at o, see 

 map), the change is more abrupt than between m and n ; in only 

 sis feet, the rock passes from soda-granite to diorite. 

 ■ A natural inference from the series of facts presented in this 

 section, those as to the flexures in the schist as well as the changes 

 at the junction of the schist and granite, would be that the heat of 

 metaraorphism increased from the limestone northward toward the 

 granite and diorite region, the heat being a consequence in part, if 

 not chiefly, of the movement and friction attending the flexing, and 

 that consequently there was produced a more and more yielding 

 condition in the material of the schist as the region of complete 

 fusion was approached, and, at the junction, perhaps a fusing and 

 obliteration of portions of some layers of the schist ; and that a 

 bed of schist existed in the granite which approached somewhat the 

 granite in character, but which, owing to the nature of its material, 

 was not wholly obliterated. 



But, are not these flexed portions of beds fragments that were 

 broken off and carried up by the fused or plastic material as it rose 

 from depths below? They lie so conformably to the flexures of the 

 schist as to suggest a negative reply to this query. 



Sections 2 and 3 (at p, and q r s, on the map) show inclusions on 

 a grander scale. 



Section 2 extends up the face of the first high bluff of bare 

 rock west of m (a bluff' that has by its east foot a path leading up 

 among the trees to a fine spring). 



Figure 10 represents a portion of the surface of the bluff about 

 forty feet wide. Below is the hard contorted schist, a well-bedded 

 micaceous schist, becoming in its upper part true gneiss ; and above 

 this, as the dotted surface shows, there is soda-granite, and then, 

 after a few yards of this rock, the diorite or hornblende rock, which 

 is indicated in the diagram by short lines instead of dots. About a 

 yard above the schist, icithin the mass of the granite, a schistose layer, 

 about a foot thick, occurs ; and eight to nine feet above this another 

 in the diorite, and hoth are conformnhle to the schist. 



The upper bed of schist shoM's (in thin slices) that it is a 

 quartzose, daik-grey gneiss, containing much black mica and 



