98 GEEEN MOUNTAINS IN MASSACHUSETTS. 



southeast. Where it crosses Dry brook we find massive limestone within 

 a few feet of the schist, and the limestone seems to dip under the schist. 

 There is also exposed in the bi'ook, near the contact, interbanded lime- 

 stone and schist near the contact of both rocks, just as observed in North 

 Adams (see p. 88). The line of contact just here is very irregular, zigzag- 

 ging, as we should expect in these crumpled, sharply folded rocks. At 

 the south end of the lenticular hill north of Dry brook the outcrops disap- 

 pear for over a mile, when we come to Tophet brook, where we have the 

 gneiss, quartzite, and limestone in close contact, as previously described. 

 From here north to the locality in North Adams described (p. 88) the 

 contact of the limestone is concealed on the east, although in places very 

 close. The structure is given on the map (PI. I and iv) by strikes 

 and dips. North of the North Adams locality no limestone in place has 

 been discovered. The head of the valley containing the north fork of the 

 Hoosic river, some 8 or 9 miles from North Adams, is formed by the 

 schists of the northern part of Hoosac mountain. The limestone evidently 

 runs up for some distance from North Adams, covered with drift, and then 

 disappears. 



THE REGION AROUND CLARKSBURG MOUNTAIN AND STAMFORD, VERMONT. 



This brings us to the last area to be described in this report, namely, 

 the mass of Clarksburg mountain, northeast of Williamstown and northwest 

 of North Adams. As will be seen by the map, the north and south forks 

 of Hoosic river unite at North Adams and flow due west through an east to 

 west valley, lying between the north end of the Greylock mass and the 

 south slopes of a high mountain mass extending down from Stamford, Ver- 

 mont, into the town of Clarksburg, Massachusetts. 



We find the Stockbridge limestone in the streets of North Adams (see 

 map, PI. i) and in the high ridge just south of the railroad, where it is found 

 in contact with and overlying the Mount Greylock Berkshire schist. The 

 latter rock is cut through by a railroad tunnel just west of the North Adams 

 depot, where the limestone forms part of the eastern side of the Greylock 

 synclinorium, really underlying the Berkshire schist, but here inverted by 

 a sharp, overturned fold. 



