Vlll PREFACE TO 



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 volcano, which 

 was formerly supposed to exist in Torres Straits. An 

 account of a remarkable bar of sandstone off Pernam- 

 buco 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 charts published in 

 various countries, my map might have been greatly 

 improved. But I hope that before long some one may 



