SUBMERGENCES. 25 



The progress of life dui'ing the eocene epoch seems to have experienced no sudden or material 

 change. Mammalian life went on gradually from the Marsupials to the rahicothcroid animals, and 

 onwards to the ruminants ; and the flora passed from the Australian to the nuocene, or North 

 American tj'pe. These changes were apparently brought about by gradual mutation in the arrange- 

 ment and distribution of land and water, possibly a gradual reduction in the temperature of the 

 globe ; but no violent or abrujjt alteration of any kind seems to have occurred. 



So far as we can trace these new modifications in the distribution of land and water, the main 

 feature seems to have been a transference of dry land from the Southern to the Northern Hemisphere : 

 that is, the submergence of land in the one, and its emergence in the other. Great alternations have 

 taken place, and are constantly taking place in this respect, everywhere. What is now above water 

 was formerly below it, and rice versa, and in each hemisphere there are jjortions intermixed ^vith 

 each other, the one of which is rising and the other sinking. And we can see that both operations 

 are carried on at the same time, and that the one is usually in compensation of the other ; although 

 both are intermingled, sometimes a general sinking with partial risings. 



The most important of such submergences seems to have been the subsidence of the vast space in 

 the South Pacific Ocean, now beaconed by the Oceanic Coral Islets which are scattered through it, 

 both east and west of the Indian Archipelago and Australia. 



It is now universally admitted that these coral islets are the relics of a submerged land which had 

 formerly existed as a great continent ; and the relations of the faunas and floras of South America 

 to New Zealand and Australia on the one hand, and to Africa on the other, as well as some 

 relations between South-West Australia and South Africa, almost compel us to admit that as comj)lete 

 a circlet of land formerly crowned the southern temperate regions as now does the northern. 



The fact that these Oceanic Islets are vestiges of a great continent was first proved by 

 Mr. Darwin. He showed that fringing reefs, — that is, reefs growing close to the land, — are an 

 evidence that the land is either stationary or slowly rising, at least that the reefs have been 

 formed when the land has been rising ; that atolls and barrier reefs, that is, reefs not clinging 

 to the shore, but separated from the land hy a space of water, show that the land has been 

 subsiding, or that a subsidence was taking place whilst they were formed ; and from this mute 

 evidence he was enabled to compile the map of elevation and subsidence by which I have pro- 

 fited. To give the evidence in support of this, woidd be to repeat Mr. Darwin's beautiful train of 

 reasoning on the subject in his " Journal of a Naturalist." The scientific reader is already familiar 

 with it, and it would be injudicious kindness to attempt to save those who are not the jjlea- 

 sui'e of reading one of the most delightful works in the English language. His argument is 

 chiefly, if not entirely, drawn from the coral reefs in these seas, and from the fact that while 

 they are composed of coral, standing on foundations of great, generally, iinfathomable depth, they 

 are yet constructed by animals requiring a foundation to start from and that foundation not to 

 be at a greater depth than twenty or thirty fathoms. 



The same fact carries the period of submergence back into the abyss of time, when the elevations 

 in the other hemisphere took place, for it proves the slow rate and consequent long duration of the 

 period during which the subsidence has been taking place. Unless the depression had been gradual, 

 the coral architects would not have had time to build up their towers and buttresses as the land 

 sank. No personal inspection is in our power here, but if we give the reins to our imagination 

 and try to guess at the scene which would meet om- eyes were a sudilini uprising equal to the 

 previous depression to take place we might find something like this to be the residt. Such an 



