THE SUPPOSED PERMANENCE [CHAP. XV. 



poraneous origin, and more than 150 or 200 miles wide, 

 seldom form part of continental land. 



4. That the Chalk, though it is an extensive formation, 

 was formed in comparatively shallow water, the depth of 

 which would have been measured by hundreds and not 

 thousands of fathoms. 



5. That no modern oceanic islands, except New Zealand 

 and the Seychelles, contain any Palaeozoic or Mesozoic 

 rocks, such as might be expected to occur in remnants of 

 old continental land. 



To these arguments it is replied that : 



1. The first statement is to a large extent true ; nothing 

 exactly like either the calcareous ooze or the red clays of 

 the modern ocean-beds has yet been found in the earth's 

 crust. It may be observed, however, that as a matter of 

 fact the limestones formed at one period of the earth's 

 history are seldom of exactly similar composition and 

 aspect to any formed at another period. Further, that the 

 resemblances between European Chalk and modern oceanic 

 ooze are so great that, allowing for a slight original diffe- 

 rence in the relative proportion of calcareous matter, and 

 for a certain amount of subsequent change, it must be ad- 

 mitted that the original condition of the Chalk was almost 

 identical with that of the ooze ; and, consequently, that it 

 was an oceanic deposit. This will be further discussed 

 under the fourth head. With regard to the red clay, even 

 if it is true that no such deposit does occur among strati- 

 fied rocks, this does not really prove more than that the 

 ancient oceans did not possess such abyssal depths as those 

 of the present day ; for the existence of this red clay seems 

 to depend entirely on depth and not on distance from land. 

 The existence of abyssal depths is surely not essential to 

 the idea of an ocean ; a wide expanse of comparatively 

 shallow water (i.e. under 1,000 fathoms) would be as 

 correctly called an ocean as a wide expanse of land which 



