181 



series to the great slate series. It is possible, as will appear 

 later, that the Hingham ledges supplement the Naiitasket 

 ledges, the basal beds of conglomerate, resting upon the 

 granite floor, having a remarkably fine development in the 

 latter, while the former afford continuous exposures of the 

 u[)[)er beds of conglomerate and the overlying slate. 



In my work on the geology of Hingham I have been greatly 

 assisted in various ways by Mr. T. T. Bouve. In fact, we 

 have traversed a large part of the ground together, have com- 

 pared notes at nearly eveiy step, and have discussed together 

 all the interpretations of the facts occurring to either. J thus 

 find myself wholly unable to determine in all cases what part 

 of the work is really my own ; but gratefully acknowledge my 

 indebtedness to Mr. Bouve for ideas as well as material 

 assistance in the field-work. Mr. Bouve has prepared a 

 general account of the geology of Hingham, which forms a part 

 of the history of the town ; and the Committee in charge of 

 this work have kindly permitted the Society to cooperate in the 

 printing of the three special maps of Hingham accompanying 

 this paper. 



TOPOGRAPHY. 



Fundamentally, or so far as the hard rocks are concerned, 

 the topogra[)hy of Hingham is based upon the westward exten- 

 sion of the broad peneplain which wc have traced in Cohasset 

 and Nantasket, and which forms the entire south shore of Boston 

 Harbor. In Hingham, as farther east, the peneplain is proved 

 by the generally uniform height of the rocky elevations ; and 

 the evidence is equally clear that the plain itself represents 

 prolonged preglacial erosion ; while the deeply channeled and 

 fragmentary form which the plain now presents nuist be 

 attributed, as before, mainly to the comparatively rapid erosion 

 attending; the strono; elevation of the land at the beG-innino: of 

 the great ice-age. Owing chiefly to the large proportion of 



