ISLAND LIFE. 



[part 1. 



continents nor continental islands existed where our oceans 

 now extend ; for had they existed, Palaeozoic and Secondary 

 formations 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 where continents noAV 

 exist, large tracts of land have existed, subjected no doubt to 

 great oscillations of level, since the Cambrian period." This 

 argument standing by itself has not received the attention it 

 deserves, but coming in support of the long series of facts of 

 an altogether distinct nature, going to show the permanence of 

 continents, the cumulative effect of the whole must, I think, 

 be admitted to be irresistible.^ 



^ Of Late it has been the custom to quote the so-called " ridge " down 

 the centre of the Atlantic as indicating an extensive ancient land. Even 

 Professor Judd adopts this view, for he speaks of the great belt of Tertiary 

 volcanoes whicli extended through Greenland, Iceland, the Faroe Islands, 

 the Hebrides, Ireland, Central France, the Iberian Peninsula, the Azores, 

 Madeira, Canaries, Cape de Verde Islands, Ascension, St. Helena, and 

 Tristan d' Acunha,and which constituted as shown by the recent soundings 

 of H.M S. Challenger a mountain-range, comparable in its extent, elevation, 

 and volcanic character with the Andes of South America" {Geological 

 Mag. 1874, p. 71). On examining the diagram of the Atlantic Ocean in 

 the Challenger Meports, No. 7, a considerable part of this ridge is found 

 to be more than 1,900 fathoms deep, while the portion called the " Connecting 

 Eidge " seems to be due in part to the deposits carried out by the Kiver 

 Amazon. In the neighbourhood of the Azores, St. Paul's Eocks, Ascension, 

 and Tiistan d'Acunha are considerable areas varying from 1,200 to 1,500 

 fathoms deep, while the rest of the ridge is usually 1,800 or 1,900 fathoms. 

 The shallower water is no doubt due to volcanic upheaval and the accumu- 

 lation of volcanic ejections^ and there may be many other deeply submerged 

 old volcanoes on the ridge ; but that it ever formed a chain of mountains 

 " comparable in elevation with the Andes," there seems not a particle of 

 evidence to prove. It is however probable that this ridge indicates the 

 former existence of some considerable Atlantic islands, which will serve 

 to explain the presence of a few identical genera, and even species of 

 plants and insects in Africa and South America, while the main body 

 of the fauna and flora of these two continents remains radically distinct. 



