FROM NATICK NOliTHWARD. 255 



carbonaceous bands assist in showing the bedding. The series can be 

 traced into the open field northward Here it rested formerly upon granite 

 and schistose rocks. An exposure in the open district, just east of the road, 

 isolated from the rest, shows among the pebbles also one derived from the 

 gneissoid schist, an interesting occurrence, since, in spite of the abundance 

 of the schistose rock in the vicinity of the basal sandstone and conglom- 

 erate series, pebbles from the schist are rarely found. The schist does not 

 seem to have furnished many pebbles, but broke up into a fine grit on 

 aerial degradation and furnished part of the finer material of the overlying 

 series. The granites also must have been considerably decayed. The 

 alteration products of the feldspars drifted farther away from the land, 

 but the quartzitic material remained nearer the shore to form the cement 

 of the basal conglomerates and the overlying arkose and sandstones; but 

 pebbles of granite are by no means uncommon, although quartzite, on 

 account of its greater durability, formed the predominating pebbles of the 

 basal conglomerates. 



The basal series of arkoses and sandstones, with scattered pebbles, may 

 be traced east of the road to a point about a mile north of the road corner, 

 where the sharp bend in the western border of the Carboniferous area occurs. 

 Here the basal beds rest upon a varied group of rocks — gneissoid schists, a 

 peculiar greenish rock of the type found in Cumberland, and granite. North 

 of this point the basal series crosses the road and follows it along its west- 

 ern side, resting upon granite as far as the next road comer northward. A 

 house stands east of the road near the point where the basal series crosses 

 the way. A short distance north the road crosses a stream. Up the stream 

 westward, in the woods, the basal series, only moderately conglomeratic 

 with granite pebbles, may be seen well exposed. A quarter of a mile from 

 the northern road corner the very steep hillside is formed by white coarse 

 sandstone, with layers of small pebbles and occasional scattered angular 

 pebbles, some of them as much as 9 inches in diameter; some of the latter 

 are granite. The underlying rock is granite. From this point the basal 

 series can be followed to a short distance south of the road comer, behind 

 a barn, where, in an open field, there is a fine exposure of the series 

 overlying the granite; conglomerate layers are frequent, often with large 

 pebbles, some of these of granite, the greater part of quartzite. From this 

 point the basal series passes northerly to a point west of the road corner, a 



