XL] HOW CHALK WAS MADE. 267 



had seen it with their bodily eyes. You must take all 

 this, of course, as truth from me to-night; but you 

 may go and examine for yourselves ; and see how far 

 your own common sense and observations agree with 

 those of learned geologists. 



The history of this great Wealden island to the 

 south-east of us is obscure enough; but a few 

 general facts, which bear upon our gravel-pit, I can 

 give you. 



I must begin, however, ages before the Wealden 

 island existed ; when the chalk of which its mass was 

 composed was at the bottom of a deep ocean. 



We know now what chalk is, and how it was made. 

 We know that it was deposited as white lime mud, at 

 a vast sea- depth, seemingly undisturbed by winds or 

 currents. We know that not only the flint, but the 

 chalk itself, is made up of shells ; the shell of little 

 microscopic animalcules smaller than a needle's point, 

 in millions of millions, some whole, some broken, some 

 in powder, which lived, and died, and decayed for ages 

 in the great chalk sea. 



We know this, I say. We had suspected it long 

 ago, and become more and more certain of it as the 

 years went on. But now we seem to have a proof of it 

 which is past gainsaying. 



In the late survey of the bottom of the Atlantic 

 Ocean, with a view to laying down the electric tele- 

 graph between England and America, by Lieutenant 

 Maury of the American navy, a great discovery was 

 made. It was found that the floor of the Atlantic 

 Ocean, after you have left the land a few hundred 

 miles, is one vast plain of mud, of some thirteen 

 hundred miles in breadth. But here is the wonder; 



