[ 557 ] 



LXIII. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from p. 325.] 



February 6, 1884.— J. W. Hulke, Esq., F.E.S., President, 

 in the Chair. 



HPHE following communications were read : — 



■*■ 1. " A Delta in Miniature. — Twenty-seven years' work." By 



T. Mellard Beade, Esq., E.G.S. 



The author described a delta deposit, which, during a period of 

 twenty-seven years, had formed in the Eake reservoir (Bivington 

 Waterworks) from materials brought down by a stream of that 

 name. The reservoir at this part was divided by a road, water 

 communication being maintained by a culvert, once 8 feet high, 

 now almost silted up. The author described the stratification of 

 these deltas ; that near the influx of the Eake consisted of peaty 

 matter, gritty sand, gravel, shingle, and boulders of Millstone-grit 

 up to about one foot diameter ; the other chiefly of fine sand with 

 some peaty matter. The former covered an area of 2508 yards, 

 with an average thickness of 2 yards ; the latter, an area of 430 

 yards, with an average thickness of 3 yards. These materials had 

 come from the drainage-area of the Eake. This is estimated at 

 1-176 square mile, and the delta being estimated at 6306 cubic 

 yards, and the time being 27 years, gives, as the annual rate of 

 denudation over the whole area, ^i_ inch per annum, or 1 foot in 

 5184 years. The mean rainfall of the Eake Brook watershed for 

 the last 10 years was 49*57 inches per annum. In this calculation 

 no account is taken of the finer materials which have doubtless been 

 distributed over the rest of the bed of the reservoir. The author 

 pointed out that this rate of denudation was rather more rapid than 

 that of the Mississippi (1 foot in 6000 years), and that the arrange- 

 ment of the materials under the varying condition of the stream 

 illustrated the phenomena of larger deltas. 



2. " On the Nature and Eelations of the Jurassic Deposits which 

 underlie London." By Prof. John W. Judd, F.E.S., Sec.G.S. With 

 an Introductory Note on a Deep Boring at Eichmond, Surrey, by 

 Collett Homersham, Esq., A.M. Inst. C.E., F.G.S. 



The wants of the growing town of Eichmond, in Surrey, have 

 necessitated the deepening of a well some years ago put down 

 into the Chalk, the water derived from which proves inadequate to 

 the present demand. The well has now been carried from a depth 

 of 434 feet to one of 1310 feet. The work of boring has been 

 performed by Mather and Piatt's flat-rope machine, under the 

 superintendence of Mr. S. C. Homersham, C.E. Only insignificant 

 quantities of water have as yet been obtained ; but that this water 

 is derived from a deep-seated source is proved by the following 



Phil. Mag. S. 5. No. 109. Suppl. Vol. 17. 2 P 



