ON THE GEOLOGY OF THE ISLAND OF AQUIDNECK. 519 
indentations have the simple structure of river excavations present- 
ing, it is true, the character of valleys which have been subject 
to other eroding forces than those which have come from flowing 
water, but still being single and rather narrow indentations in the 
axis of considerable streams. As we go to the north and east be- 
yond Narraganset Bay, we find indentations of the same general 
character ; at first, obscurely on the southern shore of Massachu- 
setts, but in great abundance snd of a perfectly comparable shape 
on the coast of Maine and the whole shore of the continent to the 
northward. Thus we see that this Bay is, in fact, the southernmost 
point of the fiord structure on our coast and is on this account a 
favorable point for the examination of the causes of the formation 
of that type of coast line. If we take a number of sections 
across the whole of the Bay at several points, say at the mouth, 
five miles from the southernmost point of land, again parallel 
thereto through the centre of the town of Newport, and further on 
in succession in an east and west direction through the upper part 
of Newport island and the island of Prudence; through Bristol 
and lastly through Fall River, we shall see’ by these diagrams 
i that the bay gives us a number of furrows and ridges having each 
| & width of from half a mile to five miles and a height or depth 
from the bottom level of from one hundred to four hundred and 
fifty feet.* If, however, we take a section in a general north and 
South direction through any of these channels of Narraganset 
Bay, we shall find that it presents us with essentially an inclined 
plane sloping pretty gradually from the northern or inner en 
toward the sea on the south. The indentations of these channels 
into their shores are comparatively few and of no great depth. 
At ome points the original islands have been soldered together by 
marine drift materials so as to destroy the original simplicity of 
arrangement, but usually throughout the Bay the contours show 
"Sa predominance of north and south reliefs. As will be seen 
by examining the contour lines of the coast survey map, On the 
= Of tobvo, the nearer ridges of the principal island con- 
m in course in a general way to the trend of the shores of the 
ang islands ; showing thereby that it is to some very general 
TR that we owe the existence of these north and south trends. 
ne NORE ean apa ane SG RES og eee 
that each we ese transverse sections are given in the diagram PI. 6. It will be seen 
from which | channel is a broad but relatively shallow excavation. The drawings 
‘Coast Sury the sections were made were carefully prepared from the records at the 
; vey Office in Washington. 
