Changes of heoel in the BeDiiuda Ishnnla. — Tarr. 295 
lands. He gives a section (p. 319), made at the dock yavd at 
Ireland island, in which the irregular surface of the base rock 
is shown to underlie the peat beds previously described by 
Jones. Descriptions are also given of the present encroach- 
ment of sand dunes upon parts of the island and a very com- 
plete description of the caves. The author previously* pub- 
lished some of the facts which were later described in more 
detail in "The Atlantic.'' 
A much more exhaustive account of the geology of the Ber- 
mudas is presented by Rice.f He mentions the discovery of 
peat beds in the center of the main island at depths of 40-50 
feet below the surface. His article contains a very complete 
description of "the difference between the base rock and the 
{Teolian sand rock and he believes that the base rock proves 
subsidence. The upper limit of the base rock above the sea 
is found to be aboiit 15 feet, where it is overlaid l)y wind- 
blown sand dunes containing land shells. He states that 
there is no evidence that this base rock is essentially older 
than the seolian. 
The movements which Rice has determined are as follows: 
"'1. A subsidence, in which tiie original nucleus of the islands 
disappeared beneath the sea, the characteristic atoll form was 
produced and the now elevated beach-rock was deposited. 2. 
An elevation, in which the great lagoon and the various mi- 
nor lagoons were converted into dry land, and the vast accu- 
mulations of wind-blown sand were formed, which now con- 
stitute the most striking peculiarity of the islands. ;?. A 
subsidence, in which the soft drift-rock around the sliores 
suffered extensive marine erosion and the shore platform and 
cliiTs already described were formed.";]; 
Fewkes§ admits local subsidence of the a^olian hills, Init 
argues that the present outline of the islands is mainly due 
to erosion. He brings forward many facts showing marked 
erosion. 
In his Bermuda Islands, [leilprin|| discusses the zoology 
and geology of the islands. His conclusions (p. 46) concern- 
*Nature, viii, 1873, 266-267, and also xiv. 1876, 97. 
tBull. U. S. Nat. MuFeuni, No. 25, vol. i. 1884. 1 32. 
tBuU. U. S. Nat. Mus., No. 25, vol. i, 1884, p. 16. 
4?Proc. Boston See. Nat. Hist., xxiii, 1884-1887, 518-522. Am. Gkol., 
v, 1890, 88-100. 
II The Bermuda Islands, Heilprin, Philadelphia, 1889. 
