WAMSUTTA GROUP. 151 



The late Prof. T. Sterry Hunt suggested 1 that these limestones inter- 

 calated with red slates might correspond with those bands of limestone 

 which are met with in similar red slates and sandstones at the base of the 

 Carboniferous formation in Canada on the Bay of Chaleur and in New 

 Brunswick. It is clear that the deposits lie near the base of the Car- 

 boniferous in Massachusetts, but the evidence is as yet lacking that this 

 section corresponds, in the sense of an exact correlation, with the base of 

 the Carboniferous in the Canadian provinces. 



Economically, these limestone beds, so far as they have been seen in 

 natural exposures, do not, in the presence of the larger and purer deposit 

 in the neighboring crystalline region of Rhode Island, assume a commercial 

 importance. As a local source of supply for individual uses, they will 

 probably from time to time afford some employment. 



ATTLEBORO SANDSTONE. 



This is a fine-grained massive sandstone, varying from green to brown 

 in color, the latter hue being due evidently to oxidation. 



The massive structure of this rock and the angularity of its particles of 

 quartz and feldspar in many cases, as seen under the microscope, make it 

 likely that it is to be regarded as a volcanic ash deposit, discharged from 

 the vents which gave rise to the felsite flows of this northwestern corner of 

 the basin. 



The most instructive exposures of this rock are in the town of North 

 Attleboro. One may be seen just west of the water tower in the north- 

 eastern part of the town. A more extensive outcrop is exposed south of 

 Groat Rock and north of the Hoppin Hill granitic area. 



Other occurrences of this rock are to be seen embedded with the red 

 series near Robinson Hill, north and east of the first-mentioned locality, 

 and again in the same stratigraphic relation in the vicinity of Deantown, 

 in Attleboro Township. The exposures along the northern margin of the 

 basin, in the Franklin quadrangle, show the position of the deposit to be 

 near the base of the Carboniferous formation. The quartz grains are there 

 much coarser than in North Attleboro. 



The stratigraphic relations of the sandstone, where seen, indicate that 



'Am. Jour. Sci., 3d series, Vol. XVIII, 1854, p. 199. 



