L 77 J 

 XI. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from vol. xx. p. 212.] 



December 2, 1885.— Prof. T. G. Bonney, D.Sc, LL.D., F.E.S., 



President, in the Chair. 



rPHE following communications were read : — 

 -*- 1 . " On some Borings in Kent. — A Contribution to the Deep- 

 seated Geology of the London Basin." By W. Whitaker, B.A., 

 F.G.S., Assoc. Inst. C.E. 



Seven deep borings in the eastern part of Kent were described, 

 all of them reaching to the Gault. The chief one is at Chatham 

 Dockyard, where, after passing through the whole thickness of the 

 Chalk, the Gault was found to be 193 feet thick ; whilst the Lower 

 Greensand was only 41 feet, and was underlain by Oxford Clay, a 

 formation not before known in Kent. 



These facts involve the thinning of the Lower Greensand from 

 200 feet at the outcrop a few miles to the south, and the .entire loss 

 of the whole of the Wealden Series, which, further south, exists in 

 great force, the Weald Clay being 600 feet thick, or perhaps more, 

 and the Hastings Beds 700 feet or more. 



Still further south, in the central part of the Wealden district, 

 there are outcrops of the Purbeck Beds, whilst the Subwealden 

 boring continues the series downwards. We have thus an addition 

 to the beds wanting at Chatham of some 400 feet of Purbeck and 

 Portlandian, of over 1100 feet of Kimeridgian, and of nearly 500 

 feet of Corallian &c. In a section of 32 miles, therefore (the distance 

 between the Subwealden and the Chatham borings), we have a 

 thinning of beds to the extent of over 3400 feet, or at the average 

 rate of about 100 feet in a mile. 



This northerly thinning agrees with the facts that have been 

 brought before us from other deep borings in and near London ; but 

 the Chatham boring is the first in the London Basin in which a 

 Middle Jurassic formation has been found. The teaching of the 

 deep borings, as a whole, is that north of the Thames older rocks 

 rise up beneath the Cretaceous beds, whilst on the south newer 

 rocks come in between the two. 



The question of the finding of the Coal-measures beneath parts of 

 the London Basin seems to admit of a hopeful answer, whilst the 

 lesson of the deep borings as regards water-supply is that there is 

 small chance of getting water from the Lower Greensand at great 

 depths underground. 



It would be well if underground exploration could be conducted 

 on a systematic plan, with proper regard to both topographical and 

 geological considerations, and not left any longer to the chance work 

 of people in search of water. 



