42 



HOOSAC MOUNTAIN. 



Deerfield rivers, branches of the Hudson and Connecticut, respectively. At 

 its southern end it is drained by branches of the Hoosatonic and by the 

 Westfield river, a branch of the Connecticut. 



The entire mountain mass is cut through at its central part from east to 

 west by the Hoosac tunnel, nearly 5 miles long, the tunnel passing almost 

 directly under the highest point of this part of the mountain, a knob one- 

 half mile north of Spruce hill, which is 2,600 feet above the sea. At the 

 extreme north of the field, half a mile south of the Vermont line, the highest 

 point is found to be 2,800 feet. Where the tunnel crosses the central part 

 of the mountain the outline is that of a double crest with a central basin or 



Fig. 0. — View looking west from slope of Hoosac mountain, east of North Adams. This gives a general idea of the 

 topography of the valley 



depression (see Profile ill, PL v), the two sides joining at the north end to 

 form the high north point and to terminate the basin. 



In its southern-central portion the mountain loses the north to south 

 ridges and drainage. It is there characterized by flat, rounded summits 

 and gentle depressions, and a frequent east to west trend of the valleys. 

 A glance at the strike and distribution of the formations will show that the 

 frequent east to west strike and extreme crumpling of the white gneisses 

 which occupy this region cause this difference in the topography. In 

 the southern part of the field a north to south strike of considerable regu- 



