EMERY MINE OF CHESTER, MASS. 45 



rocks was not as well made out by me as might have been done 

 in a more favorable season ; but as my observations accord, as 

 far as they go, with those of Dr. Jackson and Prof. Shepard, I 

 prefer inserting their observations, rather than my own, in 

 describing the geology of the emery locality. 



" The mine is situated nearly in the center of the Green 

 Mountain chain as it traverses the western border of the state, 

 at a point not far from half way between the Connecticut and 

 Hudson rivers. It is included in the metamorphic series of 

 rocks, here consisting of vast breadths of gneiss and mica-slate, 

 with considerable interpolations of talcose slate and serpen- 

 tine. The general direction of the stratification is N. 20° E. 

 and S. 20° W., the relation to the horizon varying from vertical 

 to a dip of from 75° to 80°, sometimes east, sometimes west. 



" The immediate vicinity of the mine presents a succession 

 of lengthened rocky swells with rather precipitous sides, having 

 summits between seven hundred and fifty and one thousand 

 feet above the level of the principal streams by which the hills 

 are traversed. The longer axis of the elevations generally 

 coincides with the directions of the strata. 



" The emery -vein traverses in an unbroken line the crests of 

 two of these adjoining mountains, and scarcely deviates as a 

 whole from the magnetic meridian. Each mountain is esti- 

 mated to have a length of two miles, thus giving four miles 

 extent to the metalliferous stratum, for such it may be truly 

 called, consisting as it does so largely of the metals iron and 

 aluminum. The Westfield River, here a small stream about 

 four rods in width, flows directly across the northern end of 

 the vein, dividing it into two equal portions. The height of 

 each mountain is estimated at seven hundred and fifty feet. 



" The emery-vein, whose average width may betaken at four 

 feet, is situated at the junction of the great gneiss formation 

 constituting the western flank of the mountains, with the mica- 

 slate forming the eastern slope. To speak more exactly, how- 

 ever, it lies just within the gneiss, having throughout a layer 

 of this rock of from four to ten feet in thickness for its eastern 

 wall. Nor does the mica-slate advance quite up to this outside 

 layer of the gneiss ; but in place thereof an extensive intrusion 

 of talcose slate occurs, having an average thickness of twenty 

 feet on the south mountain, and widening out at the north 



