52 History of Hingham. 



feet. These hills rest on rock surfaces which have been subjected 

 to glacial action and show striation. 



Now when the fact is taken into consideration that all such 

 hills are only to be found in countries which have been covered 

 with the ice-sheet, that their longitudinal axes always coincide, 

 or very nearly coincide, with the direction of the stria? upon the 

 rocks of the regions where they occur, and that they are com- 

 posed almost entirely of till, no one can reasonably doubt that 

 they were originally formed under and by the action of the ice- 

 sheet itself. How the till could be raised into such hills has been 

 a subject of much question, but there is now a general acquies 

 cence in the view that they had their origin in the gradual and 

 long-continued accumulation of the clay and its accompanying 

 pebbles in certain places favorable for the aggregation of the ma- 

 terial, in the same manner that sand-banks are formed in rivers. 



GROOVINGS AND STRIATION OF THE ROCKS. 



The rock exposures in different parts of the town show clearly 

 the wearing away of the material, causing extensive grooves upon 

 their surfaces, and often fine striae, which mark unmistakably the 

 course of the glacier over them. The granite, while it exhibits 

 the smooth, rounded outlines and the deep groovings on a grand 

 scale, seldom shows the finer and more delicate markings as seen 

 upon the slate and diabase. Among the localities where the stria? 

 mov be clearly discerned are the following : — 



Fort Hill. — The diorite on the side of the street next the 

 cemetery very generally exhibits stria?. An examination of these 

 shows their direction to be as follows, — compass measurement 

 (which measurement will be given in all cases) : — 



East of south 1 0° 

 East of south 1 2° 

 East of south 15° 



Lasell Street. — On the left side of this street, going south, 

 about 1000 feet from Free street, and extending from the carriage- 

 way to the fence, is the flat surface of a dike of diabase, upon 

 which are very numerous stria?. Several of these examined were 

 found to run east of south 10°. 



Beal's Cove, Weymouth Back River. — There is here a consid- 

 erable exposure of slate, through which is a large dike of diabase. 

 On both rocks stria? are abundant. Examination showed them to 

 vary in direction as follows : — 



East of south 10°, J 



East of south 15°, >on slate. 



East of south 20°, ) 



East of south 25°, on dike rock. 



