1880. J on Land and Sea in relation to Geological Time. 279 



eflfects upon the distribution of Plants and Animals ; so that, on the one 

 hand, Land-continuity has been establislied where there was formerly a 

 complete interruption ; whilst on the other, continents now for the most 

 part separated by Oceanic areas, or islands cut off from neighbouring 

 continents by deep channels, may have been at one time in continuous 

 connection. My contention is that such connections have been formed 

 by the elevation of mountain ridges (terrestrial or submarine) by 

 lateral thrust ; and not by the vertical elevation of a great area of 

 sea-bottom into a continental plateau. Thus, there appears to be 

 valid evidence that the surliice-connection between North and South 

 America is comparatively modern ; a communication between the 

 Atlantic and Pacific basins having formerly existed where now in- 

 terrupted by the Isthmus of Darien, the elevation of which probably 

 does not date back further than the early Tertiary period. So, in 

 the North Atlantic, the extension of the European platform to the 

 west of the Shetland Islands, the existence of a ridge at only about 

 200 fathoms' depth beneath the surface between the Faroes and Ice- 

 land, and of another ridge at a greater depth between Iceland and 

 Greenland, renders it not unlikely that at some former period Europe 

 and North America may have had a band of connection along this 

 line. On the other hand, the knowledge we now possess of the con- 

 figuration of the more southerly part of that Oceanic area, seems to 

 preclude the probability of the former extension of a great continental 

 platform (the hypothetical Atlantis) between Europe and America in 

 the parallel of the Azores. So, as it seems to me, the remarkable 

 relations pointed out by Sir J. D. Hooker between the Floras of New 

 Zealand, Tasmania, and South America, may be accounted for by 

 connecting ridges raised by lateral thrust, without supposing the ex- 

 istence of a vast Antarctic continent now deeply submerged.* And 

 the former connection of Madagascar with the African continent, 

 distinctly indicated by the distribution of animal and vegetable life 

 on the -western portion of the island, might easily have been esta- 

 blished by an elevation of the bottom of the Mozambique Channel by 

 lateral thrust. There are even indications, in the groups of volcanic 

 islets lying to the north-east of Madagascar, that this great island 

 may have been once in connection through them with the Asiatic 

 continent. 



Such limited and local changes, I again repeat, are perfectly con- 

 sistent with the doctrine of general permanence. And I have now, 

 in conclusion, to show how remarkably this doctrine is confirmed by 

 comparison of the deposits ascertained by the ' Challenger ' sound' 

 ings to be now going on upon the real Ocean-floors, with those in 

 process of formation on the shallow bottoms near land. 



* We still know too little about the configuration of the Sea-bed of the great 

 Southern Ocean, to enable any definite opinion to be at present formed on this 

 point. All that can be said is, that no physical evidence of the former existence 

 of such a connectiDg continent has as yet been obtained. 



