PREFA TOR Y NOTE. xiii 



portion of the proof-sheets of his book on Animal Life which 

 related to corals. 1 (This book was afterwards translated in the 

 International Scientific Series.) The letter 2 is dated 'Down, 

 October 2, 1879,' and runs thus : — 'My dear Professor Semper, 

 — I thank you for your extremely kind letter of the 19th, and 

 for the proof-sheets. I believe that I understand all, excepting 

 one or two sentences, where my imperfect knowledge of German 

 has interfered. This is my sole and poor excuse for the mistake 

 which I made in the second edition of my Coral book. Your 

 account of the Pelew Islands is a fine addition to our knowledge 

 on coral-reefs. I have very little to say on the subject, even if I 

 had formerly read your account and seen your maps, but had 

 known nothing of the proofs of recent elevation, and of your 

 belief that the islands have not since subsided, I have no 

 doubt that I should have considered them as formed during 

 subsidence. But I should have been much troubled in my 

 mind by the sea not being so deep as it usually is round 

 atolls, and by the reef on one side sloping so gradually 

 beneath the sea ; for this latter fact, as far as my memory 

 serves me, is a very unusual and almost unparalleled case. 

 I always foresaw that a bank at the proper depth beneath the 

 surface would give rise to a reef which could not be distin- 

 guished from an atoll formed during subsidence. I must still 

 adhere to my opinion, that the atolls and barrier-reefs in the 

 middle of the Pacific and Indian Oceans indicate subsidence, 

 but I fully agree with you that such cases as that of the Pelew 

 Islands, if of at all frequent occurrence would make my general 

 conclusions of very little value. Future observers must decide 

 between us. It will be a strange fact if there has not been 



1 In the original edition of this book, Professor Semper refers to the 

 subject of coral-reefs in the following words : — " Es scheint mir als ob 

 er in der zweiten Ausgabe seines allgemein bekannten Werks liber 

 Korallenriffe einen Irrthume iiber meine Beobachtungen zum Opfer 

 gefallen ist, indem er die Angaben, die ich allerdings bisher immer 

 nur sehr kurz gehalten hatte, vollstandig falsch wiedergegeben hat." 



2 Life and Letters of Charles Darwin, vol. iii. p. 182. 



