46 Geology, fyc. of the Connecticut. 



this range at the north end of Mount Tom, and on the op- 

 posite bank it rises again precipitously and forms Mount 

 Holyoke. This I found, with a nice sextant, to be eight 

 hundred and thirty feet above Connecticut river. North 

 of Holyoke the greenstone is curved towards the right and 

 continues of nearly the same elevation until it terminates 

 near the north-west corner of Belchertown, having reach- 

 ed the primitive region. 



Nine or ten miles north-westerly from this- point, we find 

 a narrow ridge of greenstone commencing, and pursuing a 

 course considerably west of north, it passes through Sun- 

 derland, crosses Connecticut river, runs through Deerfield, 

 crosses Deerfield river, and extending through a part of 

 Greenfield, terminates at the falls in Connecticut river. A 

 few rods east of this termination another range commenc- 

 es and runs east of north through Gill, with some interrup- 

 tions, till it reaches its extreme northern point in North- 

 field, two railed south of the primitive greenstone. 



It will be seen by the map, that these greenstone ridges 

 separate the old red sandstone from the coal formation 

 nearly the whole distance from Berlin to Northfield; and 

 the rocks of the coal formation are frequently found lying 

 above the greenstone. The range of green stone in Sun- 

 derland is very narrow, and being in an unfrequented spot 

 along the western margin of Mount Toby, it was a long time 

 before I discovered its existence. Having once found it, 

 however, it was traced, without much difficulty, except 

 what an almost impassable precipice presented. It is from 

 ten to eighty rods wide. As you ascend the mountain from 

 tlie west, you first pass over a formation of old red sand- 

 stone, which is here a coarse pudding-stone. Next you 

 come upon the greenstone, most of which is amygdaloidal, 

 and is, so far as hand specimens will enable us to decide, 

 the real toad stone of Derbyshire. Immediately east of 

 the green-stone you find the coarse, brownish red, and the 

 fine, fissile, argillaceous, gray and red sandstone slates of 

 the coal formation. These uniformly rise in higher ledges 

 than the greenstone; even one hundred or one hundred 

 and fifty feet above it. As you pass along in the direction 

 of the greenstone ridge, these precipices are not more than 

 ten feet from you on one hand, and the greenstone at no 



