470 G. Bowher—On the Chalk of Kent. 



part of this formation.^ He has arrived at this conclusion partly 

 from the nature of the Chalk beneath the Tertiaries and its organic 

 remains, and also from its total thickness. I would suggest, how- 

 ever, that the variations in the thickness of this deposit may not be 

 altogether due to denudation of the upper beds, but to its having 

 been deposited over an uneven sea-bed ; for if the unequal thickness 

 of the Chalk were due to its denudation, we should still find the 

 Lower Chalk of comparatively the same thickness, which is not the 

 case. Moreover, the Upper and Lower Greensand vary much in thick- 

 ness. In 1855, Mr. Godwin-Austen gave reasons for supposing a 

 possible elevation of the Coal Measures beneath the London basin ; ^ 

 and Mr. Prestwich's account of a well bored at Harwich confirmed 

 this view.'* If we compare the Chalk of Kent with that of Norwich 

 and Diss in Norfolk, Lyme Eegis in Dorset with the Chalk of Paris 

 and the Isle of Wight, etc., we find that it is not always the upper 

 but the lower divisions which have thinned out, as the following 

 table will show. 



A boring in the Chalk, lately undertaken to prove the thickness 

 of the Lower Chalk between Dover and Calais, taken a quarter of a 

 mile west of High Light, South Foreland, and four miles south-west 

 of Calais, both below high- water mark, gave the following result : — 



At South Foreland 175 Upper Chalk. 



„ „ 295 Lower „ 



470 



At Calais 270 Upper Chalk. 



„ 480 Lower „ 



750 



In the Isle of Wight Upper Chalk estimated... 1200 



White Chalk, without flints 200 



Chalk Marl , 60 to 80 



1480 



NoKwicH. Diss. 



Chalk, with flint, 6 or 7 ft. Chalk, few flints, marly ... 100 



apart 483 Chalk flints, in layers 330 



Chalk, soft and yellow 10 Grey Chalk, with flints ... 60 



Hard flints, 2 or 3 ft. apart 190 Blue Chalk 20 



Chalk, without flint 350 



Grey Chalk 102 510 



1135 



1 "Water-bearing strata of London (1851), p. 139. 



2 Journal of Geological Society, 1857, p. 249. 



