304 ANNUAL OF SCIENTIFIC DISCOVERY 



Greenfield. At Greenfield we find the Connecticut River Sandstone dipping 

 forty degrees east. Leaving the valley we strike the Calcareomica-slate in 

 Shelburne, having a dip of sixty-seven degrees east. This rock consists of 

 micaceous slates and schists interstratified with bluish-gray silicious lime- 

 stone. The dip gradually increases to thirty-eight degrees east at two and a 

 third miles from the commencement of the rock; when, upon East Mountain, 

 we find a beautiful mica-slate which cleaves into large tables, and is gen- 

 erally destitute of limestone. The dip of this is forty degrees east, and it 

 extends one and one-third miles. Then, just below the top of East Moun- 

 tain, upon the west side, there is about fifty feet thickness of hornblende 

 slate, of which the dip is twenty-eight degrees east. Passing into the valley 

 of theDeerfield River, gneiss is found, becoming gradually nearly horizontal. 

 Between this rock and the hornblende slate above, it is hard to draw the 

 line. Most of the gneiss has hornblendic layers interstratified with it 

 sparingly ; but at the top of the gneiss the hornblende predominates ; the 

 rock being in some places nothing but a heavy, unctuous, shining mass of 

 hornblende crystals. West of Shelburne Falls the gneiss begins to dip to 

 the west. The extent of the gneiss is four and one-third miles, mostly in a 

 deep valley. 



At East Charlemont the hornblende slate is found above the gneiss, cor- 

 responding in character and thickness to the same rock in Shelburne. Then 

 follows the beautiful mica-slate, sparingly interstratified with limestone, and 

 lastly the calcareomica-slate, corresponding to the rock at the east end of 

 the section. Here, at the end of the section in Charlemont centre, the strata 

 are perpendicular, running north and south, and stand side by side with 

 talcose slate. 



The Deerfield River makes a bend just above Shelburne Falls, so that the 

 section crosses the river twice, and continues for two or three miles further 

 in the valley. Had a section been measured across the river at Shelburne 

 Falls village at right angles to the stream, it would have exhibited a moun- 

 tain, west of the river, possessing all the characters of East Mountain in a 

 reverse order. Thus we find an anticlinal axis, with the same strata upon 

 the opposite sides of the ridge at their proper distances. The inference is 

 that the strata were once continuous, and that the material has been denuded. 

 A measurement upon the protracted section gives 3,350 feet, or three-fifths 

 of a mile, as the height above the present level of the former strata. This 

 is taken from the lowest level upon the section. As we go east or west from 

 this central point, the surface rises; consequently the thickness of the 

 denuded strata constantly diminishes in these directions. The denuded sur- 

 face is eleven miles wide. 



From the bend in Deerfield River above Shelburne Falls the stream con- 

 tinues westward in a deep valley for twenty miles, to Hoosac mountain, 

 before turning northwards. This valley has probably been excavated in like 

 manner; but no exact measurement can be made of the amount of erosion, 

 because the river crosses perpendicular strata. A line drawn from the sum- 

 mits on cither side of the valley to each other would give large results ; but 

 they would not be equal to the truth. 



Let us now look at the first described erosion in another light. The gneiss 

 rock at the bottom is exposed over an oval area about three miles by two. 

 If ten observers should start from the centre of the oval, and travel in as 

 many different radiating directions, they would all see the same succession 

 of rocks, and in the same order. The dip is quaquaversal, gradually return- 



