18401881] EARTH-MOVEMENTS 147 



deposit. On the whole, I lean to the side that the continents Letter 497 

 have since Cambrian times occupied approximately their 

 present positions. But, as I have said, the question seems a 

 difficult one, and the more it is discussed the better. 



To A. Agassiz. 1 Letter 498 



Down, Jan. 1st, 1881. 



I must write a line or two to thank you much for having 

 written to me so long a letter on coral reefs at a time when 

 you must have been so busy. Is it not difficult to avoid 

 believing that the wonderful elevation in the West Indies 

 must have been accompanied by much subsidence, notwith- 

 standing the state of Florida ? 2 When reflecting in old days 

 on the configuration of our continents, the position of moun- 

 tain chains, and especially on the long-continued supply of 

 sediment over the same areas, I used to think (as probably 

 have many other persons) that areas of elevation and subsi- 

 dence must as a general rule be separated by a single great 

 line of fissure, or rather of several closely adjoining lines of 

 fissure. I mention this because, when looking within more 

 recent times at charts with the depths of the sea marked by 

 different tints, there seems to be some connection between 

 the profound depths of the ocean and the trends of the 

 nearest, though distant, continents ; and I have often wished 

 that some one like yourself, to whom the subject was familiar, 

 would speculate on it. 



P.S. I do hope that you will re-urge your views about the 

 reappearance of old characters, 3 for, as far as I can judge, 

 the most important views are often neglected unless they are 

 urged and re-urged. 



I am greatly indebted to you for sending me very many 

 most valuable works published at your institution. 



1 Alexander Agassiz, of the Museum of Comparative Zoology, Harvard 

 College, Cambridge, U.S.A. 



2 The Florida reefs cannot be explained by subsidence. Alexander 

 Agassiz, who has described these reefs in detail (Three Cruises of the 

 U.S. Coast and Geodetic Survey Steamer Blake, 2 vols., London, 1888), 

 shows that the southern extremity of the peninsula " is of comparatively 

 recent growth, consisting of concentric barrier-reefs, which have been 

 gradually converted into land by the accumulation of intervening mud- 

 flats " (see also Appendix II., p. 287, to Darwin's Coral Reefs, by T. G. 

 Bonney, Ed. ill., 1889.) 



3 See Life and Letters, III., pp. 245, 246. 



