58 



wood, bones of reptiles, pebbles of quartz, jasper and slate, with 

 mica and grains of "chlorite," wliich from the prevailing colour 

 of the latter has given to this seiies of beds the name of Urcensand, 

 but as it varies considerably in its lithological character and is 

 apt to be confused by the similarity of its name, with the upper 

 Greensaud, continental geologists have called it the 

 Kecomian, from the ancient name of Ncufuhatel (Neco- 

 mum) in Switzerland, where it is very fully developed. The 

 harder nature of its rocks has caused it to resist denudation, to a 

 greater extent than the clays to the North and South of it, so that 

 it now forms the second line of escarpment running round the 

 Weald, and cTcn over-topping the North Downs at Lcith Hill near 

 Dorking, where it attains the height of nearly 900 feet. Locally it 

 is subdivided in ascending order, into the Atherfield clay, Hythe- 

 beds, Sandgate-beds, and Folkestone-beds. Subsidence in the old 

 delta seems to have taken place until the fresh-water mollusks died 

 out, and gave place to those which were exclusively marine. The 

 fossils of the Atherfield clay belonging to the latter type. The 

 Hythe-beds contain the famous Kentish ]?ag so largely used in the 

 neighbourhood of Maidstone for a building ancl road making 

 material. Margret Plues, in her excellent little book on geology, 

 states, the lime it makes is of such superior quality, that when the 

 centre arch of Aylesford bridge was removed, it had to be destroyed 

 by gunpowder. Rochester Castle and many of the Loudon churches 

 are built of this stone. These harder strata are succeeded by the 

 softer clayey Sandgate-beds, and these are replaced again by green- 

 sands, hard silicious limestone, and chert bands, so conspicuous in 

 the East Cliff of Folkestone. The fossil proper to the lower green- 

 sand are marine, but as before mentioned the river which formed the 

 old Wealden delta still continued to carry into the sea the drift 

 wood, and bones of reptiles, that we now find fossilised in the 

 lower greensaud, which must therefore have been deposited not very 

 remotely from the land which that river drained. Thus the most 

 perfect remains of the great Wealden reptile, the Iguanodon, were 

 found in a quarry of Kentish Hag, near Maidstone, by Mr. 

 Bensted. The fossil wood occurring in such large quantities at Copt 

 Point, near Folkestone, is sometimes found to have been perforated 

 by boring molluscs. The woody fibre in some examples I have ex- 

 amined has been almost entirely replaced by mineral matter, only 

 six per cent, of carbon remaining (instead of fifty, the quantity 

 contained in most woods), with eight per cent, of moisture and forty 

 of phosphate of lime. Wood coutains a minute quantity of phos- 

 phate of lime, but here we find an amount equal to that which we 

 mi"ht expect in animal remains, bones of animals and fish contain- 

 ing over fifty per cent of phosphates. The source of the phosphates 

 inl;he lower greensand, is probably the highly fossiliferous over- 

 Iviu"- Gault Clay, which contains numerous spherical bodies 



