404 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 24, 



we connect this well with others in the valley of the Lea, and add to 

 it the extra height of the hill at High Beech (deducting the gravel 

 and the Bagshot sands, and judging the heds to be almost level), it 

 will still give about 440 feet as the thickness of the London Clay. 



Figs. 1, 2. — Outline Sections of the London Clay. 



[The vertical dotted lines in figs. 1, 2, 3, & 4 mark the position of well-sections.] 



Scale.— Horiz. 1 inch to 6 miles. Vert. 1 inch to 2000 ft. 



Fig.l. — From Cheam to Hampstead. 



Sea-level. -^- 



Fig. 2. — From Northaw to Loughton. 



Sea-level. 



I. London Clay. 

 c. Chalk. 



A section from Havering-atte-Bower to Brentwood, at both of 

 which places we have traces of the Bagshot sands, passes two points 

 where the lower sands have been reached, and gives an average 

 thickness of 450 feet to the London Clay. Warley Parsonage and 

 Brook-street are both situated about 20 to 40 feet below the level of 

 the Bagshot sands, which cap the summit of the hill at Brentwood, 

 and at the former place the London Clay was found to be 390 feet 

 thick, and at the latter about 400 feet. 



Proceeding eastward, we approach the Sheppey and Southend 

 district, and here the London Clay seems to expand. As the strata 

 are apparently not much disturbed, and there are a considerable 

 number of well-sections, we can form a tolerably approximate 

 estimate, although we have no section which traverses this deposit 

 at the points where the series is complete. I will first take 

 an east and west section through Sheppey (fig. 3). At Cowling, 

 near Gravesend, the chalk is at the surface. At Sheerness, 9| miles 

 eastward from this place, three Artesian wells give respectively a 

 thickness of 347, 35G, and 347 feet to the Loudon Clay. At Queens- 

 borough (two miles south of Sheerness, and on the same level, — and at 

 the same distance from Cowling), the London Clay is 280 feet deep; 



