No. 9.— Notes on a Carboniferous Boulder Train in Eastern 
Massachusetts. 
By Myron L. Fuller. 
Introduction. 
To obtain the best results from the study of a boulder train the 
source, as pointed out by Prof. N. S. Shaler ( ’93, p. 186), should 
be of limited area and of well-defined boundary; the rock should 
be of a character which renders it readily distinguishable from all 
others with which it might be associated in the boulder train; 
and it should be hard enough to resist speedy destruction. Such 
occurrences are difficult to find in eastern Massachusetts. There 
are, indeed, small outcrops of characteristic rock in several places, 
but they are not of a nature to furnish sufficient quantities of 
material to form an easily distinguishable train. I was obliged, 
therefore, to select for my investigations a rock which had by no 
means a limited area, and which presented only a single available 
boundary. This rock, which varies from a bright red shale to 
a dull red sandstone, is the upper member of the strongly folded 
series of Carboniferous strata occupying the basin between the 
granite of the Blue Hills of Quincy on the north, and the granite 
and diorite of South Braintree and Randolph on the south (shown 
approximately by the larger of the two shaded areas on the map). 
The underlying conglomerate, the base of the Carboniferous series, 
is a coarse gray rock which usually bears little or no resemblance 
to the sandstone. There are, however, especially in its upper 
portions, certain layers of purplish or even red material, which 
are sometimes difficult to distinguish from the sandstone. These 
layers, occurring, as they do, at some distance farther east than 
the normal sandstone, would tend, but for their relative scarcity 
which limited the number of boulders furnished, to have an appre¬ 
ciable effect upon the distribution of the boulders. The field 
observations showed, however, that, with the possible exception 
of the immediate vicinity of the ledges, the effect of these layers 
of reddish material in the conglomerate could be neglected. The 
