552 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



sands. The bed was, however, everywhere disturbed by the pressure aud 

 thrust of the ice which had moved over it from north to south. 



On the western face (fig. 5) the larainge, which, being exposed in tlie 

 du-ection of the strike, had run nearly horizontal!}', have been squeezed 

 into wavy folds, and often show beautiful illustrations of reversed faults, 

 the upthrow overlying the downtlu-ow, the faults always dipping to the 

 north. On the soiithern face these faults were much more numerous, and 

 as the work of removing the earth progressed they were constantly chang- 

 ing. On one face of 10 feet I counted twenty. On the sm-face repre- 

 sented in the figure they are present in gi-eat number, and two are especially 

 marked, one faulting the bed 3 feet ; these dip 60° W. In other portions 

 the bed was thrown into entire confusion. Over a large portion of the 

 section a beautifull}^ delicate incipient cleavage has been superinduced in 

 the sands by the pressiu'e, and its existence is made manifest only by the 

 concenti-ation of iron rust in sharply distinct layers IJ inches apart, which 

 run parallel to the level base of the till above, passing across the laminae 

 of the sands and distinguishable instantly from the ordinary lines which 

 mark the lower limit of infiltrating water. Their position in the upper 

 portion of a thick permeable layer and beneath an impervious one would 

 make them difficult of explanation in that way. It seems to me that 

 the pressure has produced in the sands distinct traces of a plane-parallel 

 structure, which has favored the movement of the percolating waters in a 

 definite plane, aud with this also the deposition of the iron from the water. 

 This structure, I have no doubt, was produced within the sands when 

 frozen. 



At its base the stratum of sand is closely blended with the till, and 

 although the transition is efi^ected in the space of an inch, there is no sharp 

 line of separation. Above, the stratum is planed down to a horizontal line, 

 the laminae being cut sharply across, and the middle layer of till rests 

 upon the surface thus produced like a plank, with a clearly defined line of 

 demarcation between it and the sands it covers. It is a horizontal fault. 



It seems to me certain that when the ice moved over this mass of sand, 

 now so yielding and incoherent, the latter was frozen into a solid and rocky 

 mass, and that it was thus eroded and faulted and cleaved, and where the 

 freezing was less entii'e was swept into the common chaos of the till above. 

 In many cases the upper layers of the till contain well-rounded sand 



