243 



Notwithstanding, however, that these facts favor the disloca- 

 tion theory, I am more inclined to accept the view that the slate 

 actually underlies the conglomerate ; but now another question 

 arises, Is this the normal and original position of the slate? 

 i.e., are there really two distinct zones of conglomerate, sepa- 

 rated by a formation of slate ? I think not. The dislocation 

 theory would require us to believe that the conglomerates on the 

 north and south of the slate are the same, and to my mind this is 

 equally consistent with the view here adopted. In other words, 

 I regard these rocks as forming an inverted, closed, and doubt- 

 less more or less faulted synclinal fold. I conceive that the 

 conglomerate underlying the slate on the south is continuous 

 beneath the surface with that overlying it on the north, and that 

 the slate is folded sharply upon itself. The unquestionable fact 

 that there is a well-marked passage both ways from the slate to 

 the conglomerate is favorable to this view, and the way in which 

 the conglomerate appears to bend around the slate at the 

 western end of the belt harmonizes better with a synclinal 

 structure than any other. 



The northern band of conglomerate is not exposed on the 

 surface between the Charles liiver and Newton Centre ; but 

 that it actually exists there is plainly indicated by the abun- 

 dance of conglomerate in the drift north of Newton Upper 

 Falls, though of course it may not be represented with entire 

 accuracy on the map. There are abundant outcrops on this 

 line east of Newton Centre, and wherever discernible the dip is 

 northerly. On Grant Avenue, one-half mile north of Beacon 

 Street, a slaty band in the conglomerate dips north sixty or 

 seventy degrees. The vicinity of Newton Centre is a good 

 point to study a section of the synclinal, for there are almost 

 continuous outcrops from the amygdaloid on the south to that 

 on the north. In the vicinity of Waban Hill there are no 

 ledges, but east of Lake Street, as already stated, they are 

 as numerous as could be desired. 



As the syncline of slate expands eastwardly it probably 

 becomes more normal in form ; while the broadest portion of 



