HOOSAC MOUNTAIN. 77 



pled, the axis of the crumples running' north 20° east and having a strong 

 northerly pitch. Profile iv a , PL v, shows this feature. 



In the same way the contact between the white gneiss and the band of 

 Hoosac albite-schist can be traced south from the point where we left it. 

 Both rocks are very much crumpled, the axis of the crumples striking a 

 little east of north and strongly inclined to the north; the contact can be 

 found within a few feet; the structure of the two rocks in the large cliffs 

 can be seen on the average to be nearly perpendicular or dipping steep 

 west. The schist near the contact is the dark garnetiferous variety found 

 at the base of that rock on the top of the mountain. 



As will be seen from the map the schist forms only a narrow band, 

 bordered again on the west by another area of gneiss. 



We will now take up the relations of the granitoid gneiss and white 

 gneiss-conglomerate and trace them around from the point where they were 

 last seen at the turn. As said above the line runs obliquely down the moun- 

 tain side, the structure of the two rocks dipping gently east; that is to say, 

 the white gneiss dips in under the granitoid instead of overlying it. Near 

 what is marked Southwick creek on the map the granitoid gneiss reaches 

 its most westerly extension and its lowest topographical level, and from 

 here the outcrops begin to rise and to turn gradually and run southeast. 

 PI. v, Profile vu, which runs up Southwick creek, shows this relation well; the 

 white gneiss has a steady flat moderate easterly dip carrying it under the 

 granitoid gneiss. At about this point we notice a transition from the white 

 gneiss to the granitoid; the white gneisses are coarse and very feldspathic, 

 so that it is almost impossible to find any definite line of demarkation 

 between the two rocks. Continuing a third of a mile south from Southwick 

 creek we come to the place where Profile x, PI. V, crosses the contact of the two 

 rocks. The actual junction of the two rocks is found here in so far as there 

 can be said to lie a junction. The strike is north 40° west and the dip 15° 

 east. Within a hundred feet horizontal the rock forms a transition between 

 the coarse typical granitoid gneiss on one side and the fine-grained banded 

 white gneisses on the other. From here the contact turns and ascends the 

 mountain rapidly, the coarse transitional gneiss making it always impos- 

 sible to find any exact contact; the strike is north 25° west and the dip 



