10 GREEN MOUNTAINS TN MASSACHUSETTS. 



point was therefore gained when the hypothesis advanced to us by Mr. 

 Putnam that the surface exposure of granitoid gneiss was a Hat, overturned 

 anticlinal fold was corroborated by Mr. Wolff. Mr. Wolff also discovered 

 that the schist beds in the white gneiss on the western flank belong to the 

 series above the white gneiss, and are simply remnants left in compressed 

 troughs overturned to the west under the overturned anticline just men- 

 tioned. 



The next step was made by Mr. Wolff in the determination that the 

 white gneisses are clastic rocks, while the coarse granitoid gneiss shows no 

 trace of clastic origin. This pointed to a closer relation between the white 

 gneiss and the conglomerate, from the fact that one or the other was found 

 to overlie the granitoid gneiss. This question also was settled by Mr. Wolff 

 by tracing out the lateral transition from the conglomerate into the white 

 gneiss. 



Finally the upward transition from the white gneiss and from the con- 

 glomerate into the schist was observed. 



Messrs. 1 'utnam and Wolff had observed, and T had traced later at several 

 points on Clarksburg mountain, a strict conformability between the lamina- 

 tion of the granitoid gneiss and that of the overlying conglomerate and 

 quartzite, the continuation of the great quartzite belt of Vermont; and later 

 Mr. Walcott had found, near the same contact, numerous casts of Ohnellus, 

 showing the lower part of the quartzite to be of Lower ( !ambrianage. Later, 

 Mr. Wolff, in tracing this quartzite northward along the eastern flank of the 

 o-ranitoid gneiss of Clarksburg mountain, found it to pass by lateral transi- 

 tion along the strike into well-defined white gneisses like those of Hoosac 

 mountain. Later still a similar transition was observed between the true 

 quartzite and the Hoosac white gneiss on the northern side of the Dal ton 

 hills. 



There still remained to lie explained the nature of the relation between 

 the granitoid gneiss and the overlying clastic rocks, and the conformability 

 that exists between the structure of the granitoid and that of the overlying 

 mcks. Prof. Emerson, working on the map in Hinsdale, found an area of 

 granitoid gneiss overlain bv the conglomerate, and concluded, from the re- 

 lation of the two rocks over broad areas, that they are there structurally 



