20 THE AGE OF THE EARTH 



million years as the time during which the stratified rocks 

 were formed. 



Before leaving this part of the subject, I cannot refrain 

 from suggesting a line of inquiry which may very possibly 

 furnish important data for checking the estimates at 

 present formed by geologists, and which, if the mechanical 

 difficulties can be overcome, is certain to lead to results 

 of the greatest interest and importance. Ever since the 

 epoch-making voyage of the Challenger, it has been known 

 that the floor of the deep oceans outside the shallow shelf 

 which fringes the continental areas is covered by a peculiar 

 deposit formed entirely of meteoric and volcanic dust, 

 the waste of floating pumice, and the hard parts of 

 animals living in the ocean. Of these latter only the 

 most resistant can escape the powerful solvent agencies. 

 Many observations prove that the accumulation of this 

 deposit is extremely slow. One indication of this is 

 especially convincing : the teeth of sharks and the most 

 resistant part of the skeleton — the ear-bones — of whales 

 are so thickly spread over the surface that they are con- 

 tinually brought up in the dredge, while sometimes a 

 single haul will yield a large number of them. Imagine 

 the countless generations of sharks and whales which 

 must have succeeded each other in order that these in- 

 significant portions of them should be so thickly spread 

 over that vast area which forms the ocean floor. We 

 have no reason to suppose that sharks and whales die 

 more frequently in the deep ocean than in the shallow 

 fringing seas ; in fact, many observations point in the 

 opposite direction, for wounded and dying whales often 

 enter shallow creeks and inlets, and not uncommonly 

 become stranded. And yet these remains of sharks and 

 whales, although well known in the stratified rocks which 

 were laid down in comparatively shallow water and near 

 coasts, are only found in certain beds, and then in far less 

 abundance than in the oceanic deposit. We can only 

 explain this difference by supposing that the latter ac- 

 cumulate with such almost infinite slowness as compared 

 with the continental deposits that these remains form an 



