202 



Cove and Otis Hill; and the monocline can be clearly traced 

 still farther in the ledges of Melville Garden and in the three 

 sedimentary islands of the harbor. Westward from the 

 Garden, however, this monocline, of east-west strike and 

 southerly dip, (;hanges gradually but rapidly to a north-south 

 strike and westerly dip, pliniging down against the great mass 

 of melaphyr already described. 



It is obvious from this sketch of the geological structure that 

 while, as previously stated, folds of various types are the 

 dominant form of displacement and give character to tlie area, 

 the flexures are [)rofoundly modified by longitudinal and 

 transverse faults. Tiie correct interpretation of these main 

 structure lines is evidently essential to the determination of the 

 stratigra{)hic elements or the normal succession of the strata. 

 Of the four sections accompanying the special maps, three are 

 approximately complete, viz.: (1) the section south of the 

 granite, througli the village; (2) the section from Beal Street 

 to Beal's Cove; and (3) the section from jNIclville Garden west 

 toward Unit's Cove. They agree in their main features and 

 especially in showing repeated alternations of coarse and fine 

 sediments. But a more careful comparison reveals the fact 

 that they cannot be exactly correlated or synchronized ; and we 

 are obliged to recognize, even in this limited area, important 

 lateral changes in the character or thickness of individual strata ; 

 sandstone at one point being represented by conglomerate or 

 shale at another, and so on. The following table of the strata 

 of Hingham has been compiled from the first and second 

 sections referred to above, and, with the foregoing qualifica- 

 tions, may be regarded as substantially correct. The individual 

 beds are subject to constant variations in thickness ; and since 

 the outcrops are unfavorable to exact measurements, tJie thick- 

 nesses given are, as the round numbers indicate, simply 

 approximations. Some of the beds attain the maxinuun 

 thickness in the one section and some in the other ; and hence 

 the totals do not correspond to the actual sections. 



