• 
The following theories are held in regard to the origin of this 
conglomerate:—(i) that in carboniferous times, another glacial 
period covered this part of the continent with an ice sheet, and 
that these great accumulations of boulders were transported hither 
from distant ledges and left by the thawing ice. A serious ob¬ 
jection to this theory is the fact that the boulders do not bear the 
scratches which characterize glacial boulders. Another theory 
is that the bay at that time was a gulf leading northwards into 
Arctic regions, and that icebergs, broken off' from some Arctic 
glacier, floated southwards, and, thawing as they reached a 
warmer latitude, deposited their burden of pebbles and boulders 
here, just as they are doing to-day on the banks of Newfoundland. 
Another theory is that the place of these conglomerates was orig¬ 
inally occupied by a finely stratified quartzyte or mica schist, 
formed during an earlier geological period and of marine origin, 
as indicated by the presence of the Brachiopoda, and that the 
action of the sea ground up the entire deposit into pebbles, by a 
process similar to that we see going on along our shores to-day. 
Still another theory is that a strong and swift river current opened 
in those times into the bay, and rolled the stones to their present 
place from some shore or hillside to the north. Each of these 
theories contains an element of probability. The large size of the 
boulders and the absence here of strata of their identical character 
are remarkable facts. 
However that may be, after the formation of the conglomerate 
came a period of comparative tranquility, during which the u Coal 
Measures, ” measuring here some 2000' were deposited. To ac¬ 
count for alternating beds of coal, slate, and conglomerate, it is 
customary to suppose alternating periods of submergence and 
emergence. Under this theory the prospect from the Aquidneck 
Island of the carboniferous time must have greatly varied. There 
were long periods during which a supposed observer would have 
looked out only upon the broad arms of the bay, others during 
which his eyes would have rested, at least northward, northwest¬ 
ward, and northeastward, on a landscape bearing some resem¬ 
blance to that of the Dismal Swamp of Virginia or the Everglades 
of Florida, and such periods recurred alternately. 
During the close of the carboniferous period, changes of a 
