360 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 ac- 

 count of the Pellew Islands is a fine addition to our knowl- 

 edge 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 eleva- 

 tion, and of your belief that the islands have not since sub- 

 sided. 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 usu- 

 ally 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 be- 

 neath the surface would give rise to a reef which could not 

 be distinguished 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 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 

 veefs. 



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 excel- 

 lent. There is nothing about M. Wagner, as I expected to 



