30 Dr. £. C. A^. van Hoepen 



to the parallelism of the mountain ranges south of Buenos Aires 

 and on our south west coast. Just now mountain ranges south 

 of Buenos Aires were mentioned which have a NW.-SE. trend 

 and which have therefore the same trend as mountain ranges on 

 our south-west coast. The South American mountains have 

 therefore a trend which is nearly rectangular to the two thousand 

 meter line of their coast. The mountain ranges near the west 

 coast of the Cape Province are practically parallel to this coast, 

 and therefore if the South American coast is fitted on to the 

 African west coast it will be found that the mountain ranges 

 South of Buenos Aires, the Sierra Tandil and the Sierra de la 

 Ventana, make a large angle with the Olifantsbergen, Bokke- 

 veldbergen and Cederbergen of the Cape. 



Stromer draws attention to the fact that the Cameroon line, a 

 tectonic line running from the Cameroon Mountain perhaps to 

 St. Helena, passes from the sea bottom into the continent, and 

 that this could not be if Africa were floating on the heavy rocks 

 constituting the sea bottom. Where this must be accepted as a 

 proof of the stability of the African continent, it can still be 

 argued, that it is America which is floating away from Africa. 



Another hypothesis is that of the permanence of oceans and 

 continents. A weighty argument in its favour is, that there would 

 not be place for the enormous masses of water, which would be 

 displaced by a South Atlantic or a Gondwana continent. If 

 deep sea ever existed on places which are now land, it would be 

 possible to prove this from deep sea deposits there. However,, 

 real unquestionable deep sea deposits have not been found on any 

 continent yet. 



Another group of evidence is based on biological facts. The 

 occurrence of the same species or genera or allied forms in two 

 continents is very often explained by connecting them through 

 land bridges. From the number of common or allied forms is 

 Judged the distance in time of the existence of the land bridge. 

 When the percentage is high the land connection was recent. In 

 this way we come to land bridges in recent times across the Medi- 

 terranean and the Red Sea. However, it has also been thought 

 necessary to have a land bridge between West Africa and Brazil 

 in Tertiary times in order to explain the occurrence of fresli 



