226 ADDITIONAL GEOLOGICAL NOTES 



Company at Walthamstow in i868-6g, south of those now being 

 made. The sections in the river deposits of Walthamstow 

 Marshes, closely resembled, as might be expected, those within 

 the newer and more northerly reservoirs. And Dr. Woodward 

 adds, that while the depth of the general floor within the 

 reservoirs nowhere exceeded lo feet, " the trenches made for the 

 ' puddled walls ' in the centre of the artificial embankments went 

 down to a depth of 20 to 24 ft." 



The details preserved by Messrs. Sharrock and Spencer 

 show a very much greater amount of variation as to the depth of 

 the London-clay beneath the river deposits in the new reservoirs, 

 than has been met with elsewhere in the district. At the 

 neighbouring spots already mentioned the depth varied from 

 10 to 24 ft. In the more northerly of the new reservoirs, the 

 " Banbury Reservoir," the London-clay was generally reached 

 in the puddle-trench on its eastern border (near the edge of the 

 marsh) at depths of from eight to nine feet. At other parts of 

 the reservoir boundary the depth was greater, the variations 

 being, however, very gradual, and the greatest depth reached 

 being 26 ft. at the most westerly point of the reservoir, a few 

 yards due east of the rifle butts. In the boundary bank of the 

 southern, or Lockwood, reservoir the variations were much 

 greater and more sudden. Starting from its southern end, I was 

 informed that a few yards west of the old channel of the 

 Lea,'' London-clay was found at a depth of 13 ft., and at 25 ft. 

 at a similar distance east of it. Proceeding in a northerly 

 direction, along the western side, as far as Stonebridge Lock, 

 the greatest depth was 23 ft. and was met with close to the Lock. 

 Along the eastern side London-clay was deepest at a point about 

 due west of the northern end of "Low Maynard Reservoir," 

 being there 36 ft. below the surface. The average on the 

 eastern side was from 20 to 25 ft., or very nearly the same as 

 that of the western side from Stonebridge Lock southward. 

 But on the western side, from Stonebridge Lock to the north- 

 western end of the reservoir, the London-clay gradually becomes 

 deeper, and was found to be, at the north-western corner, 57 ft. 

 below the surface of the marsh. Then, 60 or 70 yards east of 

 that point, in the northern boundary, the clay was only 15 ft. 

 below. 



3 See Map, Essex Naturalist, vol, .di.. p. 2 (igoi). 



