x.] ON A riECB OF CHALK. 189 



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 bottom 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-cast 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 remains are often 

 in the most exquisite state of preservation. The valves 

 of the shell-fishes are commonly adherent ; the long 

 spines of some of the sea-urchins, which would be de- 

 tached 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 process 

 of covering up, or, in other words, the deposit of Globi- 

 gerina skeletons, did not go on very fast. It is demon- 



