The far-reaching eflfect of this variety of surface will be more 

 clearly apparent if we note what would be the extent of change 

 supposing the superficial Gravels, the London Clay, the Chalk, and the 

 Lower Greensand to be wanting in Surrey. Granting the table to be 

 correct the number of absent species would be 19+14+55 + 28=116, 

 i.e., 11-8%. 



The relative positions, in asce?iding order, of the various geological 

 strata of our District may be thus tabulated for convenience of 

 reference : — 



Secondary Period. 



Cretaceous 



Tertiary Period. 



Eocene (Lower) 



Pleistocene. 



Recent Period. 



Lower 



Upper 



Wealden. 



Lower Greensand. 



Gault. 



Upper Greensand. 



Chalk. 



Thanet Beds. 



Woolwich and Reading Beds. 



Oldhaven Beds. 



London Clay. 



High-Level Gravels. 

 Low-Level Gravels. 



Alluvium. 



Secondary Rocks. 



Weald Clay. — There is a narrow tongue-like strip at the base of 

 the gorge cut by the Medway through the Greensand, extending from 

 the main body to a point below West Farleigh ; at Maidstone only 

 covered by 7 or 8 feet of river gravel. 



Atherfield Clay. — A still narrower strip included between the 

 Weald Cla)' and the Alluvium-bordered river. It rises from below, 

 and follows the sinuosities of the Greensand escarpment, of which it 

 is the basal member. The rapidity with which this clay yields to sub- 

 aerial denudation, as compared with the resistant nature of the 

 overlying rocks, is the cause of the steep Greensand escarpment. 



Lower Greensand. — This crops out from below the gault at the foot 

 of the great chalk escarpment, and stretches away south for some five 

 or six miles, rising gradually and terminating with the escarpment 

 above mentioned, upon the edge of which are grandly situated a series 

 of villages, as Linton, Chart Sutton, Sutton Valence, Boughton, etc., 

 whence magnificent views can be enjoyed of the fine country beyond. 

 Good sections may be seen at Maidstone, Loose, Boughton, etc. 



Gault. — Mostly consists of a stiff blue clay. It forms a belt of 

 about an average width of three-quarters of a mile, rising from below 

 and running half parallel to the chalk escarpment, which owes its 



