432 The International Geological Congress Postponed. 



If these islands be permitted for tlie above reasons to be called 

 non-oceanic, then, by a slight stretch, the same courtesy may be 

 extended to S. Georgia (96 miles long and 10 broad), ^ for the chain 

 of the Andes, where it enters Tierra del Fuego, takes a turn to the 

 eastward, and the eastern cape points direct to S. Georgia. The 

 rocks of Tierra del Fuego consist of clay-slate,^ and so also do those 

 of the Falkland Islands, which lie between it and S. Georgia. This 

 similarity of composition points to a former connection. 



Without committing oneself to an opinion upon the profitableness 

 or otherwise of reconstructing the geography of past periods of the 

 world's history, one cannot help seeing that this great question of 

 the permanence of ocean basins is one of fundamental importance. At 

 one time I was quite disposed to reject the theory, as does Mr. Mellard 

 Eeade. But the course of study which I went through in writing 

 my Physics of the Earth's Crust led me to change my opinions, on 

 grounds rather physical than geological. If there is any weight in 

 the arguments I have there put forward, they give a support to the 

 theory from a fresh point of view. 



Extensive changes of level seem to me to be the most difficult to 

 account for of all the phenomena of geology. And the greater the 

 changes, the greater the difficulty. The permanence of the respective 

 areas seems therefore to involve less difficulty than their interchange. 

 I published in " Nature," " about two years ago, a suggestion to 

 account for the origination of ocean basins. It is rather remarkable 

 that the first and only allusion to ir which I have seen has just 

 now come from New Zealand in Dr. Haast's address at Canterbury 

 College.^ Accepting Professor Darwin's theory that the moon broke 

 away from the earth more than fifty million years ago, I think the 

 ocean-basins maj^ be the scar that was formed, and that the base- 

 ment rocks of continents are fragments of the crust which had 

 already solidified, and which were left behind. It has since occurred 

 to me that the Archaean rooks may be veritable remnants of it. 

 I would refer to my published article for the details of the grounds 

 on which I think this theory plausible. Dr. Haast uses rather too 

 strong an expression in saying, that I have attempted to prove it. 

 It is probably incapable of proof, even if true. 



0. Fisher. 



THE INTERNATIONAL GEOLOGICAL CONGRESS POSTPONED. 



SiK, —Will you allow me to announce in your columns that the 

 International Geological Congress which was to have been held in 

 Berlin next month is postponed to September, 1885, in consequence 

 of the outbreak of cholera in the South of Europe. 



■WOODWARDIAN MuSEUM, ThOS. MoKeNNY HuGHES. 



Cambuidge, Auff. 12th, 1884. 



1 Darwin's Naturalist's Voyage, p. 248. 

 ■-' Scrope's Volcanos, 1862, p. 434. 

 3 "Nature," Jan. 12, 1882. 

 * "Nature," Apr. 24, 1884, p. 609. 



