40 History of Hingham. 



however, that can be said in favor of the view that all the gran- 

 ites and other rocks of the region, hitherto considered Archa3an, 

 are more recent than the Primordial, including even those of the 

 well-known Quincy Hills. Indeed, the evidence that this is the 

 case is well-nigh conclusive. Certainly there can be no question 

 but that considerable areas of the granite were fluent and erup- 

 tive after the primordial slates were formed. A very valuable 

 and instructive article was published in the Proceedings of the 

 Boston Society of Natural History in 1881, by Professor M. E. 

 Wadsworth, on the relation of the Quincy granite to the primor- 

 dial argillite of Braintrec, in which he demonstrated that in dif- 

 ferent localities the granite was eruptive through the slates, as 

 shown by the close welding of both rocks, and by the effect of 

 the contact in altering the character of both near the line of 

 junction. 



After the events narrated, the area of the basin became one of 

 slow subsidence that must have continued through a vast period 

 of time, as during its ages the oreat bodv of the rocks that form 

 the conglomerate series was formed, — the conglomerates and sand- 

 stones near the margins of the coasts, and the slates, the material 

 of which was deposited by the rivers, in the deeper portions. As 

 subsidence continued, the sea encroached more and more upon its 

 shores, the margins of the land became more remote, and the 

 great body of the slate was gradually laid down in the deep 

 waters to a thickness of more than a thousand feet. 



Before proceeding further in the history of the basin, the writer 

 will express views long held by him relative to the origin of the 

 pebbles that made up the great body of the conglomerate in- 

 cluding the sandstone, which is only rock of the same character 

 formed of finer material, and of the slates. 



Of the conglomerate it may be said that the formation of this 

 rock wherever found has generally been regarded as mainly due 

 to the action of water, and its existence in the Boston Basin has 

 been ascribed to the force of the waves beating for countless gen- 

 erations against, and making an inroad upon, the coast, resulting 

 in the wearing down of the rocks, and the formation by attrition 

 of the bowlders and pebbles which subsequently were cemented 

 into compact strata. This view the writer does not concur in, as 

 he judges it impossible that in any number of ages the action of 

 the waves alone on the area of the basin could have led to the 

 production of such a body of bowlders and pebbles as make up 

 the conglomerate. He believes there was a far more potent cause 

 for their origin silently at work moulding them into form long 

 anterior to their submergence in the surging waters. This cause 

 is to be found in the highly corrosive character of the atmosphere 

 in the early ages of the earth's history, by which the hills, origi- 

 nally of course but rock elevations, became under its action rap- 

 idly disintegrated. Such elevations of early periods in southern 

 regions yet exist as monuments of this corrosive action, for the 



