GEOLOGY place they form a band on the south of the Kennet past Inkpen and extending almost to the county boundary. There are a number of outlying patches of Reading Beds, some with cappings of London Clay. They mostly lie on rather high ground. Then there are some small patches near Cookham and a large one near Wargrave. Yattendon stands on one, and there is another near Fril- sham. There are several north of Newbury, one of which runs out from Newbury to Wickham. There are also a number of small outliers dotted about on the Chalk near Basildon, Aldworth, Great Fawley, etc. The Reading Beds are a great deal hidden by alluvium and gravel. They consist in the main of clay though important beds of sand occur. The clay is often mottled, red, blue, orange, etc. Beds of pebbles occur in places. The thickness, according to Mr. Blake, varies from about 70 to 90 feet, but it is a little less in places. Good supplies of water are to be obtained from the sands and it is often soft in character. The Reading Beds, as has been said, rest upon a greatly eroded surface of Chalk, but it is a fairly even surface and is usually covered by holes or perforations filled with sand. These perforations are prob- ably often the work of boring shell fish, or, as Mr. W. H. Hudleston has suggested, they may in some cases be due to the roots of seaweed. Upon this Chalk floor lies the bottom bed of the Reading series consisting of green loamy sand with pebbles of flint. These pebbles are derived from the Chalk and show to what a large extent the Chalk had been eroded before the deposition of the Reading Beds. The bottom bed also contains flints which are of irregular shapes and have not been at all waterworn or rolled. They have become externally green and are usually spoken of as ' green-coated flints.' At Reading, Newbury, Kintbury and other places this bottom bed contains great numbers of oyster shells, usually Ostrea bellovacina, but at least one other species occurs. The two valves of the oysters are fre- quently united and they are not rolled or waterworn, showing that they lived where we find them. In some places at Reading there are two distinct oyster beds a foot or so apart. A few marine shells and many sharks' teeth occur in the bed. This bed of oysters has long attracted attention. It is referred to by Robert Plot in his Natural History of Oxfordshire (folio, Oxford, 1705), p. 1 20. He remarks that ' at Cats Grove near Reading they met with a bed of oyster shells both flat and gibbous about 12 or 14 foot under- ground, not at all petrified, all of them opened except some very few that I suppose have casually fallen together, which how they should come there without a deluge seems a difficulty to most men not easily avoided.' Dr. William Stukeley in Itinerarium Curiosum (folio, London, 1724), p. 59, also refers to this locality. He says that 'near the trench the Danes made between the river Kennet and the Thames is Catsgrove 15
