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four hundred feet. Single cliffs cut the strata at right angles for 

 seventy-five feet or more. According to the explanation of the 

 structure here offered, the beds on the north, which, in conse- 

 quence of the faulting, appear to underlie those to the south, are 

 probably the newer ; and this is in harmony with the fact that 

 the finest material is found in the most northerly ledges. The 

 remaining part of Hull is marked on the map as slate : although 

 between the southern end of Nantasket Beach and Point Aller- 

 ton, a distance of more than three miles, there is not a single 

 outcrop. The loose materials, shingle and drift, however, 

 include a large proportion of slate and considerable sandstone ; 

 but, so far as I have observed, little or no conglomerate. 



Planter's Hill is probably entirely composed of granite ; and 

 hence there is, apparently, no stratigraphic connection, on the 

 land, between the uncrystallines of the Nantasket area and those 

 of Hingham Harbor and the district to the westward. The islands 

 in this harbor are all conglomerate, with, I believe, southerly or 

 south-easterly dips ; and ledges of the same rock are prominently 

 placed in the Melville Garden, at Downer Landing; but there 

 is scarcely enough fine material included to furnish a clue to 

 the structure. Between Hingham Harbor and Weymouth Back 

 River, however, the key to the stratigraphy is unquestionably 

 to be found in the disposition of the granite and amygdaloid ; 

 the complication observable originating chiefly in the large tri- 

 angular mass of amygdaloid east of Hewitt's Cove. In this 

 area of about two square miles, we find the structure so char- 

 acteristic of the Nantasket beds, and resulting from disloca- 

 tions., combined with sharp synclinal and anticlinal folds. As 

 for the Nantasket area, the map is here only approximately cor- 

 rect, the general outlines alone being given. 



Otis Hill and the hill south-west of Crow Point are of drift 

 formation. On the west side of the last-mentioned elevation, 

 near the base, there is conglomerate, a continuation of that in 

 Melville Garden, with a westerly dip of 10°— 30° ; this passes 

 upwards into grit and sandstone, and is finally overlaid con- 

 formably by perhaps one hundred feet (traverse measure) of a 



