xii LIFE OF TERTIARY PERIOD 251 



step, the formation of any such enormous connecting lands between 

 existing continents in accordance with what we know of the rate 

 of elevation and depression of land, and the corresponding organic 

 changes that must ensue. They seem to forget that such a vast and 

 complete change of position of sea and land is not really known 

 ever to have occurred. 



Let us consider for a moment what the supposed land-connection 

 between South America and Australia really implies. The distance 

 is more than half as much again as the whole length of the South 

 American continent, and 1000 miles farther than from Southampton 

 to the Cape. This alone should surely give us pause. But unless 

 we go as far south as the Antarctic circle, the depth of the 

 intervening ocean is about two miles ; and until we get near New 

 Zealand there is not a single intervening island. There are here 

 none of the indications we expect to find of any geologically recent 

 depression of land on a vast scale. Of course we may suppose the 

 connection to have been along a great circle within ten degrees 

 of the South Pole, but that will not greatly shorten the distance, 

 while we have not a particle of evidence for such a vast change of 

 climate in Mid-Tertiary times as would be required to render such 

 a route possible. .But the mere physical difficulties are equally 

 great. All land elevation or depression of which we have geo- 

 logical evidence has been exceedingly gradual, very limited in 

 extent, and always balanced by adjacent opposite movements. 

 Such movements appear to be slow creeping undulations passing 

 over continental plateaux and their immediately adjacent sub- 

 marine extensions. Sometimes the depressions seem to have taken 

 the form of basins ; but we cannot conceive of any elevation 

 of continental dimensions, or depression of oceanic character as 

 to depth and area, without the complementary movement to 

 complete the undulation. A continental extension between South 

 America and Australia would almost necessarily imply a subsidence 

 of one or both of those countries over an equal area and to an equal 

 depth ; and, so far as I am aware, no geological evidence has been 

 adduced of any such vast changes having occurred at so recent 

 a period in either continent. I believe it can now be truly said 

 that no stratigraphical geologist accepts the theory of frequent 

 interchanges of continental and oceanic areas, which are so hastily 

 claimed by palaeontologists and biologists to be necessary in order 

 to overcome each apparent difficulty in the distribution of living or 

 extinct organisms, and this notwithstanding the number of such 

 difficulties which later discoveries have shown to be non-existent. 



