THE GEOLOGY OF HOOSAC MOUNTAIN AND ADJACENT TERRITORY. 



By J. E. Wolff. 



INTRODUCTION. 



The territory embraced in this report extends from the Hoosic valley 

 in the west to the meridian of 73° on the east, and from the state line on 

 the north to the valley in the south which runs east from Pittsfield through 

 Dalton. It covers the easterly half of the "< Ireylock sheet" of the new map 

 of Massachusetts. It is an area about 18 miles in length, varying from 10 

 to 4 miles in width, and covering about 120 square miles. 



TOPOGRAPHIC WORK. 



As the extreme complication of the field required great accuracy in the 

 location of outcrops, at an early stage in the work a base-line 7,000 feet 

 long was measured on the Boston and Albany railroad in Hoosic valley and 

 a sufficient number of points were established by triangulation to allow the 

 accurate vertical aud horizontal topographic determination of important out- 

 crops, which were then plotted on a large field map on a scale of 1,000 

 feet to the inch. Subsequently the plane-table sheets of the state map (scale 

 2 inches to the mile) were utilized, and a special topographic map of that 

 part of Hoosac mountain near the tunnel (on a scale of 1,000 feet to the 

 inch) was prepared. At many places accurate section lines were run by the 

 stadia and the geological points incorporated in the general map. 



TOPOGRAPHY. 



Hoosac mountain is the name applied to a part of the Green mountains 

 situated in the northwest corner of the state of Massachusetts, near the Ver- 

 mont boundary. This region forms the watershed between the Hoosic and 



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