32 THE OCEAN RIVER 



Atlantean continent during the time of man, the earher his- 

 tory and origin of the ocean floor is by no means settled in the 

 minds of modem scientists, and there is today a new upsurge 

 of interest in the whole problem. As recently as September 

 1950 tlie British Association for the Advancement of Science 

 held a special symposium of the leading European scientists 

 at Birmingham, England, to discuss the question. As it turned 

 out, the followers of Wegener's theory of continental drift, 

 and his opponents led by the Dutch scientist J. H. F. Umb- 

 grove, were in almost equal numbers, and there were nearly as 

 many arguments pro as con. 



The amazing similarity in shape of the continental outlines 

 on opposite shores of the North and South Atlantic has already 

 been mentioned. That they should fit so neatly into each other 

 seems hardly a coincidence. We have also mentioned that some 

 biologists require a fairly recent transatlantic land connection 

 in order to account for the similarity of plants and animals in 

 Africa and South America. Wegener's theory of the westward 

 drift of the American continents away from Europe and Africa 

 at a relatively late date offers a solution satisfactory to the 

 biologists, but it is far from satisfying to many geologists. No 

 one has been able so far to give a universally acceptable expla- 

 nation of how the lighter continental masses have managed to 

 move through the less easily melted and heavier basalt beneath 

 them, though many different mechanical interpretations have 

 been put forward, the pros and cons of which are too technical 

 for discussion here. If the continents are plowing westward 

 through underlying semiplastic rocks we should expect to find 

 a submarine accumulation of rock or at least of sediment along 

 the westerly edges of the continents, much as a blunt-nosed 

 ship raises the water ahead of its bow. There are no signs of it. 

 Again, we might expect that the sediments would be thinned 

 out to the east of continents as they drifted away, but this is 

 not noticeably true. 



