THE MONSON GNEISS AND ASSOCIATED ROCKS. 41 



lustrous, with some beds gneissoid and some marked b>' the absence of 

 hornblende from spots which appear like por])hyritic feldspars but are 

 composed of a granular feldspathic mass. At the top of the liornblende- 

 schist tlie contact is also visible, and the chanye is sudden into a rather 

 coarse, .slightly rusty, gray muscovite-schist with few garnets. 



Directly across the river, back of J. Dole's house, the rather coarse 

 white gneiss is followed immediately by an arenaceous hornblende-schist, 

 gneissoid as before, and this is separated from the mica-schist above by a 

 small mineral vein. 



THE MONSOK GNEISS AND ASSOCIATED ROCKS. 



Amos Eaton says,^ referring to the gneiss x-ange east of the river: 

 "This range evidently passes under the Connecticut River, accompanying 

 the granite and covered by other strata, and rises with it on the western 

 side," and I have, myself, no hesitation in associating the bands of gneiss 

 which cross the State east of the Connecticut with the Becket gneiss on the 

 west of the river, on both lithological and stratigraphical grounds. They 

 are, however, nowhere known to come into visible contact, and in default 

 of this final pi'oof of their identity I may consult convenience and give 

 this rock also a separate name and treatment. It is the C 4 of Percival.^ 

 Beginning north of the great bend of the Connecticut, opposite Middletowu, 

 it runs north, and in a quan-y at Portland, to which I was kindly guided 

 by Prof. William North Rice, of Middletown, it is so exactly like its con- 

 tinuation farther north that in hand specimens and in mass it could not be 

 distinguished from the products of the quan-ies of Monson or Pelham. It 

 enters the State from the south in two narrow bands, separated by newer 

 rocks, and the eastern band is limited on the east by the deep sand-filling of 

 the central valley of Monson. 



The two bands of this rock, separated by an infolded complex of 

 hornblende- and mica-schists, and bounded also on the west by a repeti- 

 tion of the latter, may be followed across Monson and Wilbraham into 

 Palmer. Here they are all twisted together in extreme metamorphism to 

 form the hornblendic border of the intrasive tonalite (syenite, Hitchcock), 

 from which thev extiicate themselves in the latitude of Belcliertown village. 



I Index, 1820, p. 119. U. G. Percival, Rept. Geol. Conn., 1842, p. 233. 



