420 Crosby and Barton—Carboniferous in Massachusetts. 
We have observed many facts pointing to the conclusion that 
the Norfolk County beds were deposited in a narrow, elonga- 
ted basin, similar to that which they now occupy, that is, that 
the present borders of the belt coincide approximately, at least, 
with the original shore lines, and that any narrowing which 
the belt may have experienced is due mainly to folding rather 
than to denudation. 
Along the existing border of the belt, where, of course, the 
lowest beds of conglomerate outcrop, these are usually mainly, 
Jy 
glomerate ake meets abruptly the steep and sometimes al- 
most cliff-li 
Blue Hills is not only almost entirely composed of the débris 
of these two varieties of rock, but it is also, for the most part, 
exceedingly coarse, holding many bowlders from one to four 
feet in diameter, and these are often but imperfectly rounded. 
It is, in fact, just such material as accumulates on the adjacent 
coast to-day, where the sea beats against clifis of granite and 
petrosilex ; and, to our minds, the conclusion is irresistible 
that the Blue Hills, much higher then than now, towered cliff- 
like, above the Carboniferous sea, and marked then as now, 
the northern limit of the deposits of that age. 
From the conclusions already stated, an inference of some 
practical importance may be drawn, viz: although the Nor- 
folk County basin contains only beds of Carboniferous age, 
idee is improbable that coal will ever be discovered within its 
imits, this narrow trough having become filled with sediments 
and converted into dry land, before the deposition of the true 
coal-measures began, and this later-formed series having been 
always, apparently, restricted to a comparatively small part of 
the main or Narragansett basin. 
