754 ON THE GEOLOGY OF THE ISLAND OF AQUIDNECK. 
In this view of their history, these conglomerate beds become a 
most important source of information concerning the ancient ge- 
ology of this part of tle continent. The geologist, in studying 
the character of glacial drift on this island or any other part of the 
continent, easily becomes convinced that he has in that mass a 
key to the geology of the country for sixty miles or more to the 
northward. Much of the rock within that region whence came 
this débris is now hidden by similar accumulations of glacial 
materials, so that the most painstaking student may fail to find its 
true character, but each gravel or boulder bed is a museum wherein 
the north lying rocks are more or less well represented. By ex- — 
amining a number of such exposures of the drift it is possible 
to determine with accuracy the range in character of materials 
which would be found in the region to the northward so far as 
Worcester or the neighborhood of Boston. In the same way we 
may interrogate the conglomerate of the coal period in this region 
for information concerning the character of the materials of that 
time exposed to erosive action in this part of the continent. The 
answer to this inquiry is that the surface of the country was then 
made up of syenites, porphyries, felsites, argillites and related 
rocks much as at the present day ; some of these rocks contained 
fossils which may well have lived during the primordial time when 
they were formed. It is perfectly clear, however, that within the re- 
gion where these pebbles were formed, there were no rocks of Silu- 
rian or Devonian age, else their. evident fossils would have been 
preserved as well as the lingule in the pebbles of the conglom- 
erate. This argument gives an important confirmation of the view 
held by some American geologists, but hitherto resting on insuff- 
cient foundation, that New England was elevated above the level 
of the ocean before the close of the Silurian period. As the region 
between Newport and the Boston and Albany Railroad contains an 
assemblage of rocks which may be taken as representative of a 
large part of the rocks of Massachusetts, it may be regarded as 
probable that we had, at’ the time when this conglomerate was 
deposited, the same conditions prevailing among the rocks of tha 
state as now prevail there. The work of metamorphism which 
_ has so much affected the character of the rocks of this region was 
_ already done-at this the beginning of the coal period. The syè- 
> nites which have been brought to the surface by the old disloca- : : 
