276 OKIGIN OF LIFE IN AMERICA 



as we find them upon the existing continents, and concludes 

 that there cannot be yet other continents with their own 

 burdens of sediment hidden beneath the ocean. That former 

 continents .of any antiquity or magnitude are not hidden 

 beneath the waves, says Professor Joly, seems certain, 

 unless the estimates of sediments are quite erroneous. 

 Whether the estimates are correct is a question which must 

 be left to authorities in physical chemistry ; but it has been 

 argued by Professor Carthaus * that the waters of the 

 ocean, as well as those of continents, were originally rich in 

 sodium chloride, and that fresh-water organisms only came 

 into existence comparatively recently, that is to say in late 

 Mesozoic times. When we consider the enormous area of 

 North America that was under water in Cretaceous times for 

 instance, less than an equivalent strip of land in the shape of a 

 trans -Atlantic land bridge would be all that is required for our 

 purpose. We need not call it a continent. 



As for the arguments in favour of the permanence of con- 

 tinents and ocean basins raised by Sir Archibald Geikie and 

 Dr. Wallace, they are based on the following facts and 

 assumptions, viz., great ocean depths, absence of abysmal 

 rocks on present land surfaces, and absence of older Mesozoic 

 or Palaeozoic rocks (with one or two exceptions) on oceanic 

 islands. It has been shown, however, by Professor Suess that 

 great depressions on the surface of the earth's crust are not 

 necessarily old or permanent. Quite near the south-west 

 coast of Asia Minor, and close to the mighty Ak Dagh (10,000 

 feet high) , a depth of over 10,000 feet has been recorded. This 

 depth is all the more remarkable when we consider that fresh- 

 water Pliocene beds of the mainland are continued across to 

 the neighbouring island of Ehodes, thus showing that the 

 latter was, until such a recent geological period as the Plio- 

 cene, still joined to the continent. Altogether Professor 

 Suessf inclines to the view that geological evidence does not 

 prove, nor even point to a permanence of the great depths, 

 at least in the oceans of the Atlantic type. The next point 

 which has been raised in favour of the view of the permanence 



* Carthaus, E., " Klimatische Verhaltnisse der Geologischen Vorzeit." 

 t Suess, E., " Are Great Ocean Depths Permanent?" pp. 182186. 



