80 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 21, 



Such, then, is a brief account of the strata and fauna of the Lower 

 Eocene deposits as seen in the Portsmouth sections. It remains to 

 determine the position which these beds may be supposed to occupy- 

 in relation to the cliff-sections at Alum Bay and WhitecHff. The 

 evidence of the fauna, including as it does many species respectively 

 of a high and low level in the Eocene strata, is too contradictory to 

 be of much value. The stratigraphical evidence which it is my good 

 fortune to be able to lay before the Society, however, is perfectly 

 conclusive. 



I propose to show this in two ways : — Eirst, by comparing the 

 ascertained rise per hundred feet of the beds described with their 

 distance from the known outcrop of higher and lower formations ; and, 

 secondly, by the more direct evidence of borings and well-sections. 



Evidence of Thickness of Beds hy Horizontal Measurement. 



I have shown that the rise of the strata along the line of the 

 section (fig. 1), from south to north, equals a rise of about 1 foot in 

 every 22 feet. Now the distance from the outcrop of the highest 

 beds exposed on the works to the known outcrop of the underlying 

 Red Clay is about 6000 feet, which gives a thickness of about 275 

 feet to the intermediate beds, or within 25 feet of the thickness of 

 the London Clay and Bognor series of "Whitecliff. Then, again, the 

 distance from the line of strike of the higher beds on the works to the 

 nearest known outcrop of the Bracklesham beds is about from 6500 

 to 7000 feet, giving a thickness to the intermediate strata of from 

 295 to 315 feet. And this thickness agrees very nearly with that 

 of the Lower-Bagshot strata at "Whitecliff. Supposing these measure- 

 ments to be correct, the strata above described must represent nearly 

 the upper portion of the London Clay of the Whitecliff and Alum- 

 Bay sections. 



Evidence hy Borings and Well-sections. 



The thickness of the strata exposed on the works in open cuttings 

 I have shown to amount to about 127 feet. A boring has been recently 

 sunk from almost the lowest of these beds to a further depth of about 

 115 feet (fig. 3, h). The details of this boring are as follows :— 



Details of boring in Extension Works, ft, ir,_ 



Sandyclay 10 



„ with more clay 5 



Stiff clay 5 



Very stiff clay ( = " Clay with Osif^-ea" of the Section) 18 • 



Claystone 3 



Very stiff clay 29 



Layer of Pyrites and a small shell ( Turritella) 1 



Stiffclay 12 8 



Claystone 2 



Clay 2 



Claystone 2 



Verystiffclay , 10 10 



Clay full of rounded black pebbles 9 



Hard sand 22 3 



Blue clay 39 



Total 155 1 



