9 



The topographic descriptions given us by the elder Hitchcock 

 and other writers, and the general evenness of the surface, 

 obviate the necessity for extended remarks under this head here ; 

 and, furthermore, the trends of the principal water-courses and 

 shore lines are sufficiently obvious on the map. I would call 

 attention, however, to the general relation of the topographic 

 features to the geologic structure, — a point likely to be over- 

 looked in a level and drift-covered region like this . The prev- 

 alent line of strike in Massachusetts, as is well known, is 

 north and south, and in the western half of the State there are 

 no exceptions of importance to be noted. East of the Nashua 

 valley, however, a north-east and south-west strike prevails, 

 especially in Essex and Middlesex Counties ; a comparatively 

 limited area in the south-eastern part of Worcester County 

 and the adjacent portion of Rhode Island exhibits a strike at 

 right angles to this, or north-west and south-east ; while among 

 the Paleozoic strata a nearly east and west strike is most com- 

 mon. That "geology is revealed in topography" is a trite 

 axiom of the science, which is well exemplified, even in this 

 extensively glaciated region. In a recent paper in' the Ameri- 

 can Naturalist,^ " On the Surface Geology of Eastern Massa- 

 chusetts," I have discussed at some length the relations of the 

 topography of this district to the glaciating agent and to the 

 geologic structure. The general conclusion reached is', " that, 

 comparatively speaking, the ice-cap rested lightly upon the 

 land, and that the topographic features having a skeleton or 

 framework of rock are, as a rule, of pre-glacial origin." In 

 other words, to quote further, " it appears probable that if the 

 present mantle of drift were entirely removed from the face of 

 the country, leaving a surface of naked rock, we should have in 

 all important respects a restoration of the pre-glacial contours. 

 And this ancient topography having been, as I conceive, 

 fashioned mainly by agents more subtle than an ice-cap, and 

 hence taking a deeper hold on geologic structure, would, if thus 

 undisguised, reveal a closer correspondence with the sti'ucture 



' Vol. XI., pp. 577, et seq. 



