GREENSAND AND PALiEOZOIC ROCKS UNDER LONDON. 903 



the hope of obtaining a better supply of water from the Lower 

 Greensand, Messrs. Meux & Co. resolved to carry a boring down 

 through the remainder of the Chalk and the Gault, in the hope of 

 reaching the former formation. 



The level of the surface at the brewery is 85 feet 7 inches above 

 Ordnance datum, that of the Kentish-Town well being 186 feet 

 6 inches. A new bore-hole, of the large diameter of 13 inches, was 

 commenced. At 840 feet the bore-hole was reduced to a diameter 

 of 9 inches, and from 902 feet for the remainder of the depth to 7 

 inches. The clean, regular cores, often many feet in length, of the 

 several formations passed through brought up by the diamond-boring 

 process are very remarkable. 



The Chalk was found to have a total thickness of 652 \ feet, while 

 at Kentish Town it is 645 feet thick ; the Upper Greensand 28 feet, 

 and at Kentish Town 13f feet* ; the Gault 160 feet, and at Kentish 

 Town 130| feet. Here the similarity ends. At the base of the Gault, 

 a seam from 3 to 4 feet thick of phosphatic nodules and quartzite 

 pebbles was met with. Under this, the bore-hole entered a sandy 

 calcareous stratum of a light ash- colour, which passed into a com- 

 pact light-coloured or white limestone, and then into a rock having 

 the appearance of an oolite, being composed of fine calcareous grit in 

 a calcareous paste. Some portions of these strata were more sandy 

 than others, and a small quantity of mica and a few grains of 

 chlorite were occasionally to be detected. This rock was in the 

 place of the Lower Greensand, but it bore no resemblance to our 

 ordinary Lower Greensand. Fortunately, some of the beds con- 

 tained plentiful casts and impressions of shells, which were recog- 

 nized by Mr. Etheridge, of the Geological Survey, as Lower Green- 

 sand fossils. Possibly these beds may represent the middle division 

 or the Eagstone. 



The commoner forms were small species of Cardium and Ceri- 

 thium, together with a Trigonia and an Eocogyra, some corals 

 and many Foraminifera ; the only specific determinations, how- 

 ever, yet made are : — Cardium Hillanum, Trigonia alceformis, and 

 Trochocyathus Harveyanus. These, however, with the general facies 

 of the fossils, satisfied Mr. Etheridge that these beds are the repre- 

 sentatives of the Lower Greensands of Kent. 



The hopes that were hereupon raised, that, the Lower Greensand 

 being reached, the ordinary loose sands which form so large a part 

 of that formation in Kent and Buckinghamshire might be met with, 

 and a supply of water obtained, were not, however, destined to be 

 realized. 



After passing through 64 feet of these calcareous strata, the lower 

 portion of which became grey and argillaceous, the bore -hole sud- 

 denly entered, at a depth of 1064 feet, into mottled red, purple, and 

 greenish shales, occasionally finely micaceous, in parts very calcareous, 



* I have adopted Mr. Whitaker's reading (Mem. Geol. Survey, vol. iv. 

 p. 498) for the thickness of this bed, in preference to the one originally given 

 by myself ; but still there is an uncertainty on this point. 



