THE SECOND EDITION. 
IX 
of tlie Pelew Islands, which were carefully examined 
by him, some account of his objections, and I will here 
only state that his view does not differ essentially from 
that of Chamisso, which will hereafter be discussed. 
It will be seen that the evidence in favour of atolls 
and barrier-reefs having been formed during sub- 
sidence is of a cumulative nature ; and that it is 
very difficult to judge with safety respecting any 
single lagoon-island or barrier-reef, or small group of 
them, even if the depth outside the reef and the slope 
of the encircled land are both known. 
In the present edition I have added some new facts 
and have revised the whole book ; the latter chapters 
having been almost re-written. The appended map of 
the Pacific and Indian Oceans remains in nearly the 
same state as before, for I have added only two red 
and two blue circles. I have removed an active vol- 
cano, which was formerly supposed to exist in Torres 
Straits. An account of a remarkable bar of sandstone 
off Pernambuco on the Brazilian coast has been added 
to the Appendix, as this bar is protected from the 
wear and tear of the waves by a coating of organic 
bodies, in the same manner as are most coral-reefs. 
It also resembles a coral-reef in shape or outline to a 
curiously deceptive degree. If I had been better 
situated during the last thirty years, for hearing of 
recent discoveries in the Pacific, and for consulting 
