I ON A PIECE OF CHALK. 33 



Battle of Hastings. The ancestors of Terebratulina 

 caput serpentis may have been present at a battle 

 of IcJithyosauria in that part of the sea which, 

 when the chalk was forming, flowed over the site 

 of Hastings. While all around has changed, this 

 Terebratulina has peacefully propagated its species 

 from generation to generation, and stands to this 

 day, as a living testimony to the continuity of the 

 present with the past history of the globe. 



Up to this moment I have stated, so far as I 

 know, nothing but well-authenticated facts, and 

 the immediate conclusions which they force upon 

 the mind. But the mind is so constituted that it 

 does not willingly rest in facts and immediate 

 causes, but seeks always after a knowledge of the 

 remoter links in the chain of causation. 



Taking the many changes of any given spot of 

 the earth's surface, from sea to land and from land 

 to sea, as an established fact, we cannot refrain 

 from asking ourselves how these changes have 

 occurred. And when we have explained them 

 as they must be explained by the alternate slow 

 movements of elevation and depression which 

 have affected the crust of the earth, we go still 

 further back, and ask, Why these movements ? 



I am not certain that any one can give you a 

 satisfactory answer to that question. Assuredly I 

 cannot. All that can be said, for certain, is, that 

 such movements are part of the ordinary course 



VOL. VIII D 



