MOUNT GREYLOCK. 163 



on Bald Mountain, Section I, PI. xx. The presence of the lower limestone on 

 the west face of Mount Prospect and of the calcareous schist belt in the 

 Hopper, east of it, indicates that its schists correspond to those which, on the 

 east side of the range, intervene between the lower limestone (Stockbridge 

 limestone) and the calcareous benches. On the west side of Mount Prospect 

 (locality 1020), near the contact of the schist with the limestone, there are 

 alternations between the two rocks probably due to the erosion of some minor 

 folds. 1 The contact here with the limestone occurs along the 1,600-foot 

 contour, while at the east end of this section it occurs between the 1,200 

 and 1,300-foot lines, a fact already noticed by Prof. Dana. 



Between the schist boundary on the west side of Mount Prospect and 

 the Hopper brook is an area about a mile wide, in the eastern half of which 

 there are numerous outcrops of limestone, but the western half of which 

 is covered with drift. There is however little doubt, judging from the out- 

 crops north and south of the section, that this area is also underlaid by 

 limestone, and, if so, that it forms several minor folds. (Compare Section 

 I.) It is in the limestone at the foot of Mount Prospect and near the mouth 

 of the Hopper that Mr. Walcott observed "several traces of fossils," one of 

 which, he says, "appears to be the inner whorl of a gasteropod related to 

 Euomphalus or Maclurea. 2 



Along the Hopper brook, about a quarter of a mile above its junction 

 with the Green river, is a small area of quartzite long ago noticed by 

 Dewey and Emmons and also referred to by Dana. 3 In Emmons's section, 



1 Such iuterbedding or minor folding near the line of contact occurs also west of Pittsfield on 

 Hancock mountain, in the, Lebanon road. 



- Chas. D. Walcott: The Taconie system of Emmons, and the use of the name Taconic in geo- 

 logic nomenclature. Am. Jour. Sci., ser. in, vol. 35, March, 1888, p. 238. 



3 Dewey : " On the stream which issues from the Hopper is arenaceous quartz of a slaty structure, 

 which is an excellent stone for sharpening the chisels used by stonecutters." Am. .lour. Sci., ser. I, 

 vol 1, 1819, p. 341. 



Emmons : " The outcrop of the quartz occurs again two miles south, near a mill at the junction 

 of the Hopper creek and Green river. A small part only of the mass is exposed, dipping southeast 

 and towards the high range of mountains known as Saddle mountains and Greylock." Am. Geology, 

 vol. 1, part 2, pp. 12-13. 



Dana: "The quartzite of Stone hill and the quartzitic mica schist of Deer hill in Williams- 

 town may be either of the upper or lower quartzite formation, if judged only by the facts the hill 

 presents. Hut the position of these areas, in the Williamstown valley, between high ridges of hy- 

 dromica schist, suggests rather that it is the underlying Cambrian." Am. Jour. Sci., ser. in. vol. 33, 

 May, 1887, p. 410. 



