94 GKEEN MOUNTAINS IK MASSACHUSETTS. 



area of the Hoosac mountain, where its character is lost. Thus we have 

 here the case of two layers of the monoclinal scries joining to form one 

 double band, the connection made by a series of curving layers at the west 

 edge of the mountain. This conglomerate is bounded on the west by beds 

 of massive quartzite which can be traced 1>\ loose pieces along the moun- 

 tain side nearly to Dry brook, where thev connect with the quartzite of the 

 sand quarry. By what complicated crumpling this is effected it is difficult 

 to say. 



In the little brook running west down the side of the mountain, about 

 midway between Dry brook and the turn of the mountain, we have an 

 important contact between the schist (forming the large area* in the valley) 

 and the (Vermont) quartzite of the side of the mountain. The two rocks 

 are conformable, strike north 35° west, dip 30° northeast. This schist 

 extends north to the turn of the mountain, there running in east among the 

 gneisses for some distance; it is impossible to describe the contortion it has 

 undergone; it is in general a series of small minor folds whose axes dip 

 northerly with the dip of the strata. The line of outcrop is hence very 

 winding and irregular. In places just here the schist assumes the form of a 

 massive iron schist composed of quartz grains, magnetite, graphite, and 

 biotite, which is easily followed. About half a mile south of the turn it will 

 be noticed on the map (PI. i) that the gneiss (Vermont) sends a curving 

 tongue northward surrounded by schist on either side; we have in this 

 another good proof of the real duplication of layers which causes the mono- 

 clinal dip of the gneisses. The schist and gneiss are conformable and follow 

 each other closelv to the point where curving layers of schist circle around 

 the gneiss and cut it off. It is a very sharp anticlinal curve, the gneiss 

 doubling back on itself with the schist closely following. (See p. 92.) 



In a small brook flowing west at the point of the mountain, just below 

 the cross roads Ave find again the schist in conformable contact with a 

 quartzite which here overlies it. Both strike north 45° east and dip west 

 gently. A few hundred feet east a quartzite white gneiss is found overly- 

 ing the black modification of the schist mentioned above, which can be 

 traced along- in bluff's for nearly a mile, forming the base of the western 

 band of white gneiss, where it has turned to run east. About a mile dis- 



