A. E. Verrill— The Bermuda Islands, Geology. 51 
which sometimes have entered through fissures, but in other cases, 
as at Devil’s Hole, they have been put in by the proprietors. They 
make excellent fish and turtle preserves.* 
Some of the smaller bays and harbors are evidently only sinks of 
this kind that have become connected with the sea by the erosion of 
the intervening rocks, in comparatively recent times. Others, like 
Peniston’s Pond, are just beginning to be breached by the sea. 
The soil of the islands is partly of reddish clay, partly of shell-sand, 
mixed with vegetable mold in most places. The reddish clay is the 
most important part. It is a mere insoluble residue or impurity, 
left after the decomposition and solution of the limestones by rain- 
Figure 6.—A weathered and eroded shore cliff near Bailey Bay, north shore, 
showing abrupt changes in the inclination of the layers of eolian limestone. 
water, during an immense period of time. It always contains, even 
where never cultivated, a notable per cent. of potassium salts, cal- 
cium phosphates, etc., and therefore forms a very fertile soil.t 
Much of the interest in the geology of the islands is due to the 
various features of the erosion by the sea ; surface erosion ; and the 
subterranean erosion, which has formed extensive caverns, sinks, 
tunnels or passages for subterranean streams, etc. At present there 
are no streams or springs of fresh water, owing to the porosity of 
the rocks and the limited surface of the land. , 
* For fuller descriptions see these Trans., xi, pp. 466-472; ‘‘ The Bermuda 
Islands,” pp. 54-60; also below, chapter on erosion. 
+ For analyses see these Trans., vol. xi, p. 493, and ‘‘ The Bermuda Islands,” 
pp. 81, 82. 
