EAST GEEENWIOH TO II^TATIOK. 253 



YBYj fine grained and white, with minute black specks. The cleavage 

 planes lie E.-W., dip low northerly. The western border of the Car- 

 boniferous basin probably follows the steep hillside from East Grreenwich 

 to Coweset, and thence for some distance the northern side of Drum Rock 

 Hill. The presence of (1) granite exposures near the southeastern end of 

 the hilly half a mile west of the southern end of Grortons Pond; (2) a fine 

 exposure of the quartzite and schist series at the northern end of the same 

 hill, hardly a sixth of a mile east of Natick; (3) an exposure of the same 

 series on the western side of the hill, a quarter of a mile south of the last 

 locality, and (4) a series of exposures southwest of the third locality, along 

 the road leading directly south from Natick, in order — quartzite, then gran- 

 ite, then quartzite again — tends to show that the present western border 

 passes only a quarter of a mile west of Gortons Pond and thence north- 

 westerly to Natick.^ 



From Natick northward the basal rocks of the Carboniferous series 

 form the steep hill front for a distance of at least 2 J miles, while the eastern 

 line of outcrops of the pre-Carboniferous series can be traced far northward 

 into Cumberland. 



The greatest interest in this border line, however, centers in the com- 

 paratively small stretch of 2|- miles from Natick northward, since here the 

 Carboniferous beds can be seen resting on the pre-Carboniferous series, the 

 basal beds containing very many angular fragments and rounded pebbles 

 derived from the older rocks, the material of these pebbles varying with 

 the character of the underlying rocks immediately adjoining. All grada- 

 tions may be seen, from the most angular fragments to well-rounded 

 pebbles. 



The quartzite-schist series is well exposed along the north side of Bald 

 Hill northward as far as Natick, especially west of the town. Near the 

 center of Natick a road leads up the very steep hill west of the town. Just 

 north of the beginning of this road is a church, below which the quartzite 

 series is exposed. Ascending the road for a distance of perhaps 100 feet, 

 turning northerly into a group of houses, the observer discovers a fine 

 exposure of the Carboniferous base resting against the quartzite on the west. 



^ The evidence leads me to beUeve that the margin of the Carbonllerous field originally lay much 

 farther to the west. It is likely, indeed, that it may have merged with what is now the Worcester 

 Basin. — ^N. S. S. 



