The Geology of Hingham. 51 



This is often called the Upper Till. It rests upon the general 

 surface of New England, overlying the true till where the latter 

 exists. It is easily distinguished from it by its somewhat dif- 

 ferent composition, containing comparatively but little clay, and 

 being much less compact, from not having been subjected to such 

 great pressure. Its color, too, is generally yellowish, arising from 

 the oxidation of the iron contained in it. 



There is yet a third glacial deposit to be mentioned ; it is known 

 as Modified Drift. This undoubtedly owed its origin generally to 

 the action of rivers, which upon the melting of the ice-sheet swept 

 over it and conveyed the rock masses, gravel, and sand, with which 

 it was laden, to many localities where they are now found. 



Having thus given an account of the origin of the drift deposits 

 and their dissemination over the surface of the land, it remains 

 for us to present the views of those who have made a special study 

 of glacial phenomena respecting the peculiar hills that prevail in 

 many sections over which the ice-sheet rested, and which form a 

 predominant feature in the topography of the town ; and also 

 of the less elevated summits and ridges known by geologists as 

 Karnes, which likewise present themselves prominently over a large 

 part of its territory. The first of these, the peculiar hills referred 

 to, are what have been called by the Irish geologists " Drumlins," 

 a name of Irish derivation, signifying a long, rounded hill, — and 

 by Professor Charles H. Hitchcock they have been called " Lenticu- 

 lar Hills," from their lenslike form. We will first dwell upon 

 these hills, upon the grooving and striation of the rocks over which 

 the glacier advanced, and upon what are known as " pot-holes," 

 as phenomena of the period under consideration ; postponing re- 

 marks upon the later drift deposits and much other matter con- 

 nected with the passing away of the ice, which will be presented 

 when treating of the Champlain Period. 



DRUMLINS, OR LENTICULAR HILLS. 



These remarkable elevations are found in many towns of east- 

 ern Massachusetts, but nowhere are seen to form more interesting 

 features of the landscape than in Hingham. Baker's Hill, Otis 

 Hill, Prospect Hill, Great Hill, Turkey Hill, and Pleasant Hill at 

 Crow Point are all elevations of this character. They are com- 

 posed, wherever found, mainly of the lowest member of the drift, 

 the till, or bowlder clay, having generally but a thin deposit on 

 their surface of the gravel and bowlders of the upper drift. They 

 vary much in size, sometimes presenting themselves as mere hil- 

 locks, but often found half a mile or more in length, and not 

 infrequently over a mile. In form they are generally oval, more 

 or less elongated, having symmetrical, rounded summits, with gen- 

 tle slopes in the direction of their longest axes and much steeper 

 ones laterally. In height they sometimes exceed two hundred 



