ON A PIECE OF CHALK 59 



state my case when I asserted that we have as strong 

 grounds for believing that all the vast area of dry land, 

 at present occupied by the chalk, was once at the bot- 

 tom of the sea, as we have for any matter of history 

 whatever; while there is no justification for any other 

 belief. 



No less certain it is that the time during which the 

 countries we now call south-east England, France, 

 Germany, Poland, Russia, Egypt, Arabia, Syria, were 

 more or less completely covered by a deep sea, was of 

 considerable duration. 



We have already seen that the chalk is, in places, 

 more than a thousand feet thick. I think you will agree 

 with me, that it must have taken some time for the 

 skeletons of animalcules of a hundredth of an inch 

 in diameter to heap up such a mass as that. I have 

 said that throughout the thickness of the chalk the 

 remains of other animals are scattered. These re- 

 mains are often in the most exquisite state of preser- 

 vation. The valves of the shell-fishes are commonly 

 adherent; the long spines of some of the sea-urchins, 

 which would be detached by the smallest jar, often 

 remain in their places. In a word, it is certain that 

 these animals have lived and died when the place 

 which they now occupy was the surface of as much of 

 the chalk as had then been deposited; and that each 

 has been covered up by the layer of Globigerina mud, 

 upon which the creatures imbedded a little higher up 

 have, in like manner, lived and died. But some of these 

 remains prove the existence of reptiles of vast size in 

 the chalk sea. These lived their time, and had their 

 ancestors and descendants, which assuredly implies 

 time, reptiles being of slow growth. 



There is more curious evidence, again, that the pro- 



