62 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



argument, is, at present, far more important than the first. Darwin 

 was, I think, the first to call attention to the absence of palaeozoic 

 and mesozoic strata in oceanic islands, and his words * which have 

 already been quoted by Mr. Wallace in ' Island Life,' will bear re- 

 peating. He says : — 



" Looking to the existing oceans, which are thrice as extensive as 

 the land, we see them studded with many islands ; but hardly one 

 truly oceanic island (with the exception of New Zealand, if this can 

 be called a truly oceanic island) is as yet known to afford even 

 a remnant of any paUeozoic or secondary formation. Hence we 

 may perhaps infer that during the palaeozoic and secondary periods, 

 neither continents nor continental islands existed where our oceans 

 now extend ; for, had they existed, palseozoic and secondary for- 

 mations would in all probability have been accumulated from 

 sediment derived from their wear and tear ; and these would have 

 been at least partially upheaved by the oscillations of level, which 

 must have intervened during these enormously long periods. If, 

 then, we may infer anything from these facts, we may infer that, 

 where our oceans now extend, oceans have extended from the 

 remotest period of which we have any record ; and on the other 

 hand, that w^here continents now exist, large tracts of land have 

 existed, subjected no doubt to great oscillations of level, since the 

 Cambrian period." 



There can be no question as to the force of this argument ; but 

 the more fully it is admitted, the more important do any exceptions 

 to the volcanic character of oceanic islands become, and the fact 

 must not be forgotten that the number of oceanic islands in which 

 palgeozoic or mesozoic beds have been found has been slightly in- 

 creased within the last few years. The Falkland Islands, the 

 palaeozoic fossiliferous rocks of which were described by Darwin 

 himself t, were not noticed by him in the paragraph quoted, doubt- 

 less because he did not regard them as oceanic : although 400 miles 

 distant from the coast of S. America, they are connected with it by 

 a bank of less than 100 fathoms deep, and they have an indigenous 

 land-mammal. But the Archipelago of South Georgia, 800 miles 

 further to the eastward and nearly 1200 miles from the American 

 continent, has now been shown to consist of clay-slate J. According 

 to the chart issued with the recently published * Challenger ' narrative,, 



* Origin of Species, 6th ed. p. 288. 



t Q. J. G. S. ii. p. 267. 



: Geol. Mag. 1884, p. 225 ; ' Nature,' March 27, 1884, xxix. p. 509. 



