XIV.] LIVING MATTER AND ITS EFFECTS. 229 



But it is otherwise with plants and animals which hve 

 under conditions more favourable for preservation ; and, in 

 which, the earthy and less perishable constituents enter in 

 large proportion into the composition of the body. There 

 is much more likelihood that the remains of animals and 

 plants which live in the sea, or in rivers, or which haunt 

 marshes and lakes, should be fossilized, than that those of 

 the dwellers on dry land should be so preserved. And the 

 greater the quantity of salts of lime, or of silica, or of other 

 slowly soluble ingredients, in the body of an animal or of a 

 plant, the longer will its fabric be in disappearing, and the 

 greater the chances of its preservation. 



Along the shores of the Isle of Sheppey, in the estuary of 

 the Thames, it is by no means uncommon to find fossils 

 which have fallen out of the clay cliffs in the course of their 

 destruction by the sea. Many of these fossils are the hard 

 fruits of trees, which lived at the time when the clay was in 

 course of formation. The fruits appear to have fallen from 

 the trees which bore them, and which probably grew on the 

 banks of a river ; and then to have been carried down by the 

 river to its estuary, where they were embedded in the fine 

 mud which has since been hardened into the clay of the 

 Sheppey cliffs. This is the same kind of clay as that on 

 which the metropolis stands — the common London clay. 

 The vegetation of this part of the world, at the time repre- 

 sented by this clay, must have been very different in character 

 from that of the present day. Many of the fruits, for instance, 

 are the produce of palm-like trees (JV/pa) akin to the screw- 

 pines, and similar to those now growing in Bengal, in the 

 Philippine Islands, and elsewhere in the East Indian Archi- 

 pelago ; while others are the cones of plants i^Protcacea) 

 similar to those which at the present day flourish in Australia. 

 Fig. 63 shows one of these fruits from the London clay of 



