536 GEOLOGY OF OLD HAMPSHIRE COUXTY, MASS. 



A careful search of the material thrown out of the ditch revealed a 

 single well-worn bowlder of the Vermont quartzite, and one of an epidotic 

 quartz-diorite (tonalite), which may have come across the valley from Hat- 

 field, but is more probably derived from the outcrop of the same rock half 

 a mile north. All the fragments, with the exception of the far-traveled 

 bowlder of quartzite, are quite angular and unworn, and the gneiss ledges 

 upon which the deposit rests is jagged and serrate, the rock dipping 25° 

 west and being jointed at right angles to the bedding. It is manifest that 

 the ice was here not polishing but rudel}' tearing up the ledge and mo^•ing 

 onward the fragments, and in several cases great masses could be seen, 3 or 

 4 feet in diameter, which had been moved but small distances from the ledge 

 and could be fitted back into the places from which they had come. A 

 coarse sand fills the interstices of the larger fragments and here and there 

 constitutes the greater portion of the mass. The whole is reddish for 2 feet 

 down, then bluish or whitish to the bottom. In one jdace it is blackened 

 with carbonaceous material for a rod to a depth of 4 feet, and below this 

 blackened area and for several feet on either side it is blue. Here a swale 

 crossed the line of the ditch and the decomposing carbonaceous material 

 deprived the infiltrating waters of the oxygen, which has over the rest of the 

 section peroxidized the iron to a depth of about 2 feet in most places, 

 though sometimes the reddening extends below the bottom of the ditch 5 

 feet. It is clear that this locality, placed high upon the eastern rim of the 

 basin and facing westward into the valley, received the full impact of the 

 ice, while the waters moving beneath the latter, produced in part,, perhaps, 

 by the very friction of the work whose efi^ects we see here so plainly, 

 washed out all the finer material into the valley below. 



The above section may be taken as a typical illustration of a deposit 

 spread in a broad, irregular, interrupted sheet on the rock over much of 

 the elevated country bordering the basin. It is irregular in thickness, dis- 

 ti'ibution, and internal structure. Upon broad surfaces of naked rock the 

 ice rested and deposited nothing, or in later times atmospheric agencies have 

 removed what was laid down. In sheltered places it was heaped up in 

 great thickness; in other places it is represented only by scattered bowlders 

 resting upon the bare ledges. And when examined as to its internal 

 structure it is found to vary greatly in the size of the stones constituting 

 the mass and in the proportion of far-traveled bowlders entering into its 

 composition. All around the valley the line of the highest lake terrace is 



