MANSFIELD: ROXBURY CONGLOMERATE. 103: 
removal by erosion, and perhaps also by displacement, of great masses 
of rock. The former idea may be called the narrow terrane view, the 
latter the broad terrane view. According to the narrow terrane view 
the Boston Basin and the Narragansett-Norfolk Basin may be con- 
sidered as originally adjacent though separated areas of deposit or as. 
separated members of one originally continuous basin. In either 
case, however, it is presumed that the combined area now occupied 
by the deposits of the several basins is approximately the same as that 
of the original deposit and that the latter was never very extensive. 
According to the broad terrane view the present deposits are down- 
folded or down-faulted remnants of a great mass of sediments which 
originally extended far beyond the present limits of the conglomerate 
areas but which have been removed by elevation above the plane of 
erosion or have been submerged beneath the sea. 
One of the strongest supporters of the narrow terrane view was 
Professor Crosby. In his Contributions to the geology of eastern 
Massachusetts he says (b, p. 181): “The Paleozoic rocks of eastern 
Massachusetts occur....only in limited basins or depressions exca- 
vated in the ancient crystalline formations. Three of the basins have: 
been recognized, and they are almost as well marked in the modern 
as in the ancient topography: for I hold the view that these basins 
probably existed as such before the deposition of the sediments which 
they contain.” The results of later studies, showing the probable: 
close relationship of the rocks in the three basins mentioned, have 
compelled a change of view so that the same author in a later paper 
speaks of the conglomerate as having been spread “far and wide over 
the entire region” (n, p. 464). Professor Shaler also speaks of the 
area of deposition as a “broad trough penetrating far into the land, 
possibly including the Worcester trough” (Shaler et al., p. 9). 
Views or Oricin.— The conglomerates have been very generally 
believed to be of marine origin. In fact up to twenty-five or thirty 
years ago there appears to have been no suggestion of any other 
possibility. One of the earlier hints of dissent from the common 
view is given by Dodge in his Notes on the geology of eastern Mass- 
achusetts. He speaks of the similarity of some features of the Rox- 
bury Conglomerate to those of glacial deposits and suggests in a 
merely tentative way the glacial origin of the conglomerate (a, p. 
408-409). The glacial hypothesis is vigorously combated by Crosby 
in his Contributions above referred to, where he maintains the 
hypothesis of marine origin (b, p. 187). Later Shaler advocated the 
