ON THE GEOLOGY OF THE ISLAND OF AQUIDNECK. 757 
pebbles, which have been observed, retained their scratches. In 
view of the fact that the larger part of our drift beds do ex- 
_ hibit this characteristic in some of their pebbles it must be allowed 
_ that this seems a serious difficulty in the way of the hypothesis that 
_the conglomerate pebbles were formed by glacial agency. It is to 
_ be noticed, however, that all these conglomerates show the effects 
of water action in the rearrangement of the fragments and can only 
_ be compared with that part of our drift along our shores which 
has been rearranged in a similar manner. We find on examina- 
tion that all those beds of drift pebbles which come within the 
submergence left on our shores have lost the traces of ice ac- 
_ tion which they generally bear on their surfaces; the facet-like 
faces are retained, but the scratches are, in all the instances which 
Ihave examined, quite worn away. Moreover, the boulders of this 
ancient period have undergone so much pressure even in those 
_ eases where there has been no great mineralogical change, that in 
almost all the localities which I have examined, distinct marks of 
change in form are quite evident. Such changes would nec- 
_ exterior markings as glacial scratches. Taking the assemblage of 
_ characters observable in this conglomerate, I am inclined to think 
_ that it was formed in great part beneath the level of the water, the 
_ pebbles and cement being transported by glacial agency and de- 
ited in the ancient sea just as they are now being carried and 
deposited by the glacial streams‘on the Greenland coast. 
The connection between the carboniferous period and a preced- 
ing epoch favoring the deposition of extensive beds of conglomer- 
ate is a fact well established both in this country and Europe. 
The conglomerate and grits which underlie the coal are generally 
made up of materials which appear to have been transported for con- 
siderable distances. This detrital epoch which is so generally 
cated by the subcarboniferous formations can best be accounted 
by supposing that the forest period of the carboniferous age 
preceded by a glacial period of great duration and intensity. 
During this ice time and immediately succeeding it there would 
e been, along the shallow border waters of the old continents, 
t accumulations of pebble beds and sandstones, which would 
throughout the stratifying action of water. During the 
of reélevation, which would have followed an ice time then, 
these beds 
followed the ice time which has just passed away, 
