402 MESSRS. H. W. MONCKTON AND E. S. HEREIES 



34. The Bagshot Beds of the London Basin. By H. W. Monckton, 

 Esq., P.G.S., and E. S. Heeeies, Esq., B.A., P.G.S. (Read 

 June 9, 1886.) 



Intboduction. 



The following communication is intended as a supplement to a 

 paper read before the Society by one of the authors in 1883 (Quart. 

 Journ. Geol. Soc. vol. xxxix. p. 348), and the two together form an 

 amplification of an article on the same subject by Mr. W. H. 

 Herries (Geol. Mag. dec. ii. vol. viii. p. 171). 



In our last paper we devoted our attention almost entirely to the 

 Upper and Middle Divisions of the Bagshot series. We now propose 

 to treat more fully of the Lower Division, and to show that the 

 occurrence of pebble-beds is by no means confined to one horizon 

 in the Bagshot series, as would seem to be supposed by some 

 observers. 



In the interval much has been written about the geology of the 

 Bagshot district, no less than five papers by the Bev. A. Irving, and 

 one by Mr. Hudleston, having appeared*. 



The views lately advanced by Mr. Irving are very much at 

 variance with the hitherto accepted interpretation of the geology of 

 this district, and to a great extent we find ourselves compelled to 

 difi'er from him. He considers (Quart. Journ. Geol. Soc. vol. xli. 

 pp. "506, 507) that the Upper and Middle Bagshot beds, in some 

 places, overlap the Lower Bagshot Beds, and rest directly on the 

 London Clay, which had been thrown into a slight syncline 

 previous to the deposition of the Lower Bagshot strata. He 

 founds his argument partly on the relative thicknesses of the 

 Lower Bagshot beds and the London Clay, as shown by weU-sections 

 at various points ; partly on the existence of pebble -beds, which he 

 appears always to refer to a particular horizon ; and partly on the 

 presence of beds and seams of clay, which he likewise considers an 

 indication that the beds in which they occur belong to a defined 



* The following are the papers referred to : — 



By the Rev. A. Irving, F.G.S. 



1883. " On the Bagshot Strata of the London Basin." Proc. Geol. 



Assoc, vol. viii. p. 143. 

 1883. " On the Bagshot Sands as a Source of Water Supply." Geol. 



Mag. dec. ii. vol. x. p. 404. 

 188.5. " Water-Supply from the Bagshot and other Strata (2)." Geol. 



Mag. dec. iii. vol. ii. p. 17. 

 1885. "General Section of the Bagshot Strata from Aldershot to 



Wokingham." Quart. Journ. Geol. Soc. vol. xli. p. 492. 



1885. " Excursions to Aldershot and Wokingham." Proc. Geol. Assoc, 

 vol. ix. p. 219. 



By W. H. Hudleston, Esq., F.E.S., RG.S. 



1886. " On a Recent Section through Walton Common exposing the 

 London Clay, Bagshot Beds, and Plateau Gravel." Quart. Journ. 

 Geol. Soc. vol. xlii. p. 147. 



