Vol. 62.] THE CLAY-WITH-FLINTS. 147 



brickearths, loams, sands, and gravels. Small patches can 

 doubtless be found which consist entirely of Clay-with-Flints ; but 

 larger tracts almost always include masses of mottled clay, sand, 

 and gravel, and sometimes accumulations of sarsen-stones, or of 

 unworn flints. 



One good instance of such associated materials has already 

 been cited (p. 138), and another may be quoted from a recent 

 memoir, as occurring in the Aldworth and Yattendon area above 

 mentioned. 1 At Buttonshaw Kiln, south-west of Aldworth, 

 Mr. Bennett saw a section showing 



' 6 feet of large unworn flints and sarsens resting irregularly on rusty-brown 

 and black-stained clay. A hole dug for clay near the kiln showed a mixture of 

 plastic clay and coarse red sand, capped with Clay- with -Flints. The plastic clay 

 seemed in process of conversion into the rusty-brown clay.' 



Let us take an actual example of the relative positions which the 

 Eocene and the Clay-with-Flints frequently occupy. For this 

 purpose I choose the large outlier of these combined deposits round 

 Yattendon and Ashampstead, west of Heading. This tract is 

 completely isolated by the valleys of the Pang and the Thames ; 

 it includes no fewer than seven outliers of Eeading Beds, connected 

 and more or less surrounded by Clay-with-Flints. At the extreme 

 north-western end (north of Aldworth) the ground rises to a 

 height of 600 feet, and there is a very small patch of Eeading 

 Beds accompanied by Clay-with-Flints at the same level. 



South-west of Aldworth is a larger outlier of Beadiug Beds, the 

 base of which descends to about 520 feet, while that of the Clay- 

 with-Flints near the same point is some 20 feet lower. On the 

 south there is a continuous tract of Clay-with-Flints, the base 

 of which falls rather rapidly to a level of about 320 feet near 

 Yattendon ; but this evidently accords with the original slope of the 

 Eocene basal plane, for a large outlier of Eeading Beds sets in at 

 Yattendon, its base sloping south-westward from about 350 feet to 

 a little below the contour of 300 feet. At the same time, the 

 Clay-with-Flints thins out rapidly against the Eocene boundary. 



The other Eocene outliers lie on a similar sloping surface of 

 Chalk, and the base of the connecting tracts of Clay-with-Flints 

 slopes in the same direction, that is, south-westward : but its border 

 passes below the level at which any Eocene is exposed, until it reaches 

 the contour of 300 feet. 



Again, there are cases where a kind of Clay-with-Flints seems 

 to overlap onto the border of an Eocene tract. On this point, 

 Mr. Osborne White informs me that he believes such overlap to be 

 of frequent occurrence, although it is not easy to prove the fact, 

 because it is very seldom that a continuous section from the surface 

 of Chalk to the surface of Eocene is actually exposed. At 

 Cadmore-End Common (Oxfordshire) he has seen a section 10 feet 

 deep, showing Eeading Beds (mottled loam) overlain by brown loam 

 full of white angular flints, both being covered by a loamy soil full 



1 'Geology of the Country around Eeading' Mem. G-eol. Surv. 1903, p. 60. 



