On the lea valley. 227 



Thus it appears that the average depth from the surface of 

 the London-clay, in the puddle-trenches of the new reservoirs, is 

 about 18 ft., and that its normal variations are from g to 10 ft. on 

 the one hand to about 25 ft. on the other. And this result -.oin- 

 cides with that obtainable either from Dr. Woodward's remarks 

 on the puddle-trenches of the more southern reservoirs, or from 

 the sinkings and borings given in Mr. W'hitaker's Memoir. 

 Thus, while in the boundary of the Banbury reser^-oir the 

 London-clay cannot be considered to be at an abnormal depth 

 anywhere, in the " Lockwood Reservoir " it appears to be 

 abnormally deep at its north-western corner, where it is 57 ft., 

 and on its eastern side, close to the northern end of the " Low 

 Maynard Reservoir," where it is 36 ft. below the surface. And 

 a line drawn across the reservoir through these two spots would 

 doubtless mark the position of the narrow subterranean hollow 

 in the London-clay which may, or may not, attain its greatest 

 depth at the north-western corner. A continuation of this line 

 northward would bring it to a point a little westward of the most 

 westerly point in the northern reservoir where, as we have seen, 

 the London-clay was deeper than at any other spot in its boun- 

 dary bank. 



I am informed that where the thickness of the beds above 

 the London-clay was greatest, in this depression, the material 

 composing them consisted of gravel, sand and silt, much resem- 

 bling that of the river deposits elsewhere. And the direction of 

 the narrow line of depression seems to be nearly due north and 

 south, or very slightly west of south and east of north. But 

 whether the somewhat unusual depth of 26 feet, at which the 

 London-clay was found at the western end of the Banbury 

 reservoir, indicates the nearness of a more noteworthy depression 

 beneath the Rifle Butts, we have no evidence to determine. 



The paper " On a Deep Channel of Drift in the Valley of 

 the Cam, Esse.\," by Mr. W. Whitaker,' appears to me to 

 describe some drift-filled hollows which are all akin to that 

 beneath Lockwood reservoir, while one example has a specially 

 strong resemblance to it. Mr. Whitaker gives details of wells 

 at Quendon and Rickling, Newport and Wendon, which all 

 show a very great and wholly unexpected thickness of the 

 Glacial-gravel and sand, which underlies the Boulder-clay, 



3 y. /. Geol, Soc, vol. Ixvi., p. 333 (1890), EbSEX Naturalist, vol. iii., p. 140 (1889). 



