24 BULLETIN OF THE 
Discussion of the Evidence afforded by the Attleborough 
Series. 
The facts as given above concerning the rocks of the Attleborough sec- 
tion and the neighboring parts of Rhode Island carry our information con- 
cerning the condition of the Atlantic coast line much further than might 
at first sight be supposed. In the first place, they prove that the Atlantic 
coast line was during the Cambrian period not far removed from its pres- 
ent position. The great thickness and general character of the conglom- 
erates appear to me to be abundant evidence on this point. Whether the 
formation of these conglomerates was due to glacial action or not, it is 
clear that they were deposited near the coast line. Only by the action 
of water moved by strong currents could we have had the stratification 
induced which appears in many of these pebbly sections. Such rapid 
movements of water are only possible in shoal regions. The fact that 
the pebbles have apparently all been derived from rocks in the immedi- 
ate neighborhood, those which lie to the westward of the Cambrian 
deposits, indicates that, while the Cambrian region was sea, the neigh- 
boring district was in a condition to yield detritus to erosive forces, and 
was therefore presumably land. We thus fix the marine shore line of 
the continent in this area close to the present coast. 
It may be here remarked, in passing, that we have now determined 
four stages in the history of this part of the continent, in which the 
coast line was near its present position. These are as follows: the 
Cambrian, which we are now considering, the Carboniferous, which 
immediately succeeds it in the same field, the Triassic conglomerate of 
the Connecticut valley, and the probable Miocene conglomerates which 
appear at Gay Head on Martha’s Vineyard. There are two other hori- 
zons pretty well determined in which fragmental materials formed along 
the coast line exist, viz. that of the Roxbury puddingstone, which prob- 
ably belongs in the Cambrian age, possibly in the horizon of the Para- 
doxides beds, and the coarse sandstones of Cretaceous age which appear 
on Martha’s Vineyard. If we add to these the glacial conglomerate of 
the last ice period, we have a total of seven stages in the earth’s his- 
tory from the Lower Cambrian to the present day, in which the shore 
of the continent has appeared near its present position. When we re- 
member the amount of evidence going to show great erosion in this 
field since the earliest geological ages, an erosion which may have re- 
moved the evidence of coast line deposits of many different ages, we 
are struck with the fact that we have here proof as to the permanence 
