1 82 MISCELLANEA. [1874. 



C. Darwin to K. Semper. 



Down, October 2, 1879. 



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 Pellew Islands is a fine addition to our know- 

 ledge 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 subsi- 

 dence ; but I fully agree with you that such cases as that of 

 the Pellew 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 subsidence of the beds of the great 

 oceans, and if this has not affected the forms of the coral 

 reefs. 



In the last three pages of the last sheet sent I am extremely 

 glad to see that you are going to treat of the dispersion of 

 animals. Your preliminary remarks seem to me quite ex- 



