276 THOUGHTS IN A GRAVEL-PIT. [xi. 



than the sands below it, deserves the title of a new 

 creation. 



As a proof some of you may recollect, when the 

 South- Western Kail way was in making, seeing shells 

 some of them large and handsome ones Nautili, 

 taken out of the London clay cutting near Winchneld. 

 Nautili similar to them (but not the same) are now 

 only found in the hottest parts of the Indian seas; and 

 what is more, not one of those shells is the same as 

 the shells you find in the chalk. Throughout this 

 great bed of London clay, the shells, the remains of 

 plants and animals, are altogether a new creation. If 

 you look carefully at the London clay shells, you will 

 be struck with their general likeness to fresh East 

 Indian shells ; and rightly so. They do approach our 

 modern live shells in form, far more than any which 

 preceded them ; and indeed, a few of the London clay 

 shells exist still in foreign seas ; in the beds, again, 

 above the clay, you will meet with still more species 

 which are yet alive ; while in the chalk, and below the 

 chalk, you never meet, I believe, with a single recent 

 shell. It is for this reason that the London clay is said 

 to be Eocene, that is, the dawn of the new creation. 



The chalk, I told you, seems to have been deposited 

 at the bottom of a still and deep ocean. But the 

 London clay, we shall find, was deposited in a com- 

 paratively shallow sea, least in depth toward High 

 Clere on the west, and deepening towards London and 

 the mouth of the Thames. 



For not only is the clay deeper as you travel east- 

 ward, but and this is a matter to which geologists 

 attach great importance the character of the shells 

 differs in different parts of the clay. 



