241 



32. — Ox THE Recext Discovery of Siluriax Eocks in Hertford- 



SHIRE, AND THEIR ReLATIOX TO THE WaIER-BEARIKG StRATA 



OF THE London Basin. 



By John Hopkinson, F.L.S., F.G.S., etc., Hon. Sec. 



[Read 12th June, 1879.] 



Plate II. 



Several deep borings have at various times been made in the 

 neighbourhood of London, within the area known to geologists as 

 the "London Basin," principally with the object of obtaining a large 

 supply of water from water-bearing strata in or below the Chalk. 

 From these borings valuable information has been gained as to the 

 conditions in which the series of rocks underlying the London area 

 occur in their extension beneath the surface, where they have been 

 found to differ considerably in their nature, thickness, etc., from 

 their prevailing character where they "crop out" or appear on 

 the surface round the edges of the basin. Important discoveries 

 have also resulted from some of the deeper borings, — discoveries 

 which, though almost anticipated by geological induction, have 

 opened up, as will presently be seen, a new field of investigation 

 and study. Of these, one of the most interesting is the discovery 

 of rocks of Silurian age in our own county, at the jS'ew River 

 Company's boring near Ware, — a discovery which throws new 

 light upon the relations of the older rocks which other recent 

 borings have shown to underlie the London Basin. 



The main features of this London Basin, and the most interesting 

 points connected with it, both physical and paloeontological, are 

 probably well known to the members of this Society, from the 

 valuable lectures we have had from Professor Morris* and Mr. 

 Lobley;t and the principal member of this basin, the Chalk, has 

 been fully treated of, as a water-bearing formation, by the Rev. J. 

 C. ClutterbuckJ and Mr. John Evans. § I will therefore avoid, as 

 far as possible, the ground thus so ably occupied. I may, however, 

 recall to you the explanation of the structure of the London Basin 

 given by Professor Morris, || by pointing out that the section here 

 given ^ represents a series of strata which were originally deposited 

 horizontally, and which have afterwards, by the sinking of the 



* " The Physical Structure of the London Basin, considered in its Relation to 

 the Geology of the Neighbourhood of "Watford." ' Transactions,' Vol. I. p. 89. 



t " The Cretaceous Bocks of England." lb. p. 1. "The Eocenes of England 

 and their Extension in Hertfordshire." lb. p. 161. 



X " The Geology and Water-supply of the Neighbourhood of Watford." 

 lb. p. 125. 



^ " The Hertfordshire Bourne." lb. p. 137. 



II 'Transactions,' Vol. I, p. 91. 



it This section was drawn on the black board. See ' Transactions,' Vol. I, 

 p. 11, for a somewhat similar section, differing chiefly in not showing the PaUco- 

 zoic ridge. 



