Reviews — Geological Survey of England — Reading. 319 



there seems to be some thickness of Chalk exposed in several pits 

 which is referable to it. Part of the zone is well exposed in the 

 railway cutting west of Pangbourne, where the beds are bent up 

 into a slight anticlinal curve, of which a sketch is given. 



(3) The zone of Micr aster coranguinum, Leske. Along the 

 valley of the Thames the thickness of this zone is about SOO feet. 

 Exposures in quarries are numerous from Whitchurch to Shiplake, 

 and probably all belong to the same zone. 



At Mapledurham and Chazey Farm, at Caversham, and south-east of 

 Wargrave in Berkshire, similar exposures of this zone can be seen. 

 Chalk is exposed in most of the valleys in the north-western part of 

 the area, and the fields are in many places thickly covered with 

 flints. 



Beading Beds. — There is a great break in time between the Chalk 

 and the Beading Beds, which are here found resting upon it ; for not 

 only are the highest beds of the Chalk wanting in this area, but 

 a considerable series of Eocene strata which in other places is 

 found below the Reading Beds is also absent. The Reading Beds 

 accordingly here lie upon a greatly but evenly eroded surface of 

 the Chalk. 



The whole formation in this area varies from about 70 feet or less 

 to 90 feet in thickness, and is composed of variously coloured 

 mottled plastic clays and more or less loose sands ; the clays are 

 the upper part, and vary from 30 to 50 feet in thickness, the sands 

 forming the lower part, being from 20 to 40 feet thick. The 

 ' bottom bed ' consists of stiff dark bluish-grey clay from 7 to 10 feet 

 in thickness. 



The main mass of the Reading Beds extends beneath the surface 

 in the southern half of the district, and at its outcrop forms 

 a narrow band running nearly due east and west. There are also 

 several outliers resting on the Chalk to the north, some to the north 

 and others to the south of the Thames. These are described in 

 detail. 



Mr. W. Whitaker contributes many notes full of valuable 

 information on sections, well - sinkings, and borings. A section 

 given, fig. 9 (p. 29), is taken from Sir J. Prestwich's paper (Quart. 

 Journ. Geol. Soc, 1854, vol. x, p. 88) on the Basingstoke and 

 Newbury Branch Railway ; and one by Whitaker, fig. 10, at 

 Rose Kiln, south of Reading, giving excellent exposures of the 

 Reading Beds. 



The famous bed of fossil Oysters (Ostrea bellovacina, Lmk.) had, 

 it appears, attracted attention before 1699, and in a letter from 

 Dr. Brewer to Dr. Sloane (see Phil. Trans., 1700-1, vol. xxii, 

 p. 485) the writer mentions that this remarkable deposit had been 

 " exposed over an area of between five and six acres of land, resting 

 on a hard rocky Chalk, the stratum of greensand with oyster-shells 

 being nigh two feet deep." 



Dr. Buckland (in 1817), Robert Plot, author of the "Natural 

 History of Oxfordshire" (1705, p. 120), Dr. Wm. Stukeley, 

 "Itinerarum Curiosum " (1724, p. 59), and other writers are 



