OF CREATION. 53 



and one which, when understood, will perhaps clear 

 up many difficulties which have sometimes puzzled 

 Geologists; but, before offering this explanation, it 

 should be understood distinctly what is meant by 

 calling an event of this kind a break in the continuity 

 of strata or groups of strata. 



If the animated beings who inhabit the different 

 parts of the earth and sea had been at all times the 

 same ; if it were an indifferent thing to the marine 

 animals whether they dwelt in shallow water, near 

 shore, in the deeper water of bays and other shel- 

 tered places, in the open sea, near the surface, and 

 where exposed to the constant action of the tides and 

 currents, or in the great depths of the ocean, far re- 

 moved from land; and if species, thus cosmopolitan in 

 their habits, had been introduced at the first creation 

 of animals on the earth, and had succeeded one another 

 in the regular order of nature, generation after gene- 

 ration repeating the same species; then, indeed, it 

 would have been difficult, and often impossible, to 

 determine whether the various strata lying over one 

 another in any given spot were formed by continuous 

 deposits, or with intervals between them of sufficient 

 magnitude to allow of the interpolation of other beds 

 in other places. But these conditions do not obtain 

 in nature. It is well known to the naturalist, that, 

 although some animals are much more capable of 

 adapting themselves to changing circumstances than 

 others, all species are more or less limited in their 

 range, and that, in a vast proportion of cases, they are 

 very strictly limited; a change of a few yards in the 

 depth of the water, an alteration in the nature of the 

 sea bottom or in the degree of exposure to tidal action, 



