STRATA OF TILGATE FOREST. 41 



bonized foliage of unknown plants, carbonized wood, and casts of uni- 

 valves and bivalves. Carbonate of lime in lenticular crystals sometimes 

 occurs between the separations of the strata, and rounded quartz pebbles 

 in the blocks of sandstone. 



The aggregate (No. 2.) is evidently diluvial ; it lies in horizontal layers, 

 immediately beneath the vegetable mould, and varies from one to six 

 feet in thickness. It is of considerable extent, and there is scarcely any 

 inequahty of the surface, in the immediate vicinity of Hicksted, Crawley, 

 &c., where it is not exposed to view. In the upper part of the bed, the 

 chalk, limestone, sandstone, and quartz pebbles, are reduced to the size 

 of small grains ; and the bones, teeth, and other organic remains, have 

 suffered an equal degree of comminution ; in the inferior layers they are 

 considerably larger, and the chalk and qviartz pebbles less frequent. 



The chalk appears to have undergone but little change, except that it 

 has acquired considerable hardness, probably from an infiltration of crystal- 

 Uzed carbonate of lime. 



The quartz pebbles exhibit their usual characters ; they are shghtly 

 translucent, and being rubbed against each other, emit a strong electric 

 smell, with a stream of light at the line of collision. This accumulation 

 of water-worn materials is loosely united by a fine grit, apparently formed 

 by the farther disintegration of the same substances. The organic remains 

 contained in it are, with but few exceptions, reduced to very small frag- 

 ments, which offer but sHght indications of their original form. The teeth 

 and scales are the most perfect, their superior hardness having enabled 

 them in some measure to resist the action of the water. Of these, the 

 molar teeth of the anarhicas lupus, are the most abundant. The teeth 

 and scales of the monitor or crocodile, and the bones and plates of a 

 species of tortoise, are occasionally found in it ; and also the triangular 

 striated tooth, (No. 14.) and the teeth of a species of squalus, (No. 13.) 



We shall now proceed to a more minute examination of the organic 

 remains of these remarkable strata ; and by comparing them with the 

 recent genera, and species, to which they appear most nearly related, 



G 



