ae ah OR cee 
ON THE GEOLOGY OF THE ISLAND OF AQUIDNECK. 523 
to wear uniformly and so to give a very even surface to the coun- 
try they underlie. This uniformity characterizes all the region 
between the Lilly Pond and Almy’s Pond on the south and the bay 
known as Blue Bill Cove on the north, with the exception of the 
strip lying east and west between the Paradise and Purgatory 
rocks on the east and Miantonomi Hill on the west, wherein there 
are several exposures of conglomerates and slates which, wearing 
unequally, have given a broken and irregular character to the 
surface. 
At the extreme northern end of the island, between Blue Bill 
Cove and the portion of Narraganset Bay known as Mount Hope 
Bay, there is a small area of the same character as that to the 
south of Newport, brought up by a fault into contact with coal- 
bearing rocks. Here also the irregular hardness of the rock has 
caused it to wear very irregularly. 
The continuous sheet of superficial accumulations hereafter to 
be described does not have any considerable - effect in altering 
the contour of the surfaces except in the finer details of particular 
points. On the west shore of Blue Bill Cove there is a surface 
of about one hundred acres which shows a type of topography 
which occurs at a number of points on our New England shore 
and is very difficult to understand. The general surface is very 
nearly a true plane and is underlaid to the depth of more than 
thirty feet, or below low tide mark by unstratified drift com- 
posed principally of materials less than one foot in diameter. 
The surface of this plain is broken at a great number of pdints by 
depressions which recall the character of the sink holes of many 
imestone countries, though no such explanation will possibly ap- 
Ply to their formation. These depressions vary much in size 
ome of them being several hundred feet in diameter, though 
usually they do not exceed one hundred feet across, and twenty feet 
m depth. Generally their outlines are rudely circular, though 
m some cases they exhibit considerable irregularity of form. At 
Some points these cavities are so crowded together that they en- 
‘reach upon each other and the plain becomes converted into a 
_ “atped surface of a singular degree of complication. A precisely 
: ‘Similar Surface occurs on the low terrace to the south of the town 
of Quincy , Mass. The conditions both of material and environ- ; 
Tayak are the same in both cases. 
“ere are a few possible means of accounting for this arrange- 
