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THE CRETACEOUS ROCKS OF BRITAIN. 
CHAPTER XXXYl. 
THE MIDDLE CHALK IX BERKSHIRE, OXFORD¬ 
SHIRE, AND BUCKINGHAMSHIRE. 
1. Berkshire. 
From Wiltshire the basset surface of the Middle Chalk passes 
into Berkshire, and at first it occupies an area of considerable width 
south of Ashbury, Woolston, and Kingston Lisle. Along this tract 
it forms the summit of the chalk escarpment, and extends south¬ 
ward down the valleys which open into that of the Lambourn river 
to and beyond the town of Lambourn. 
From Sparsholt Down eastward the summit ridge is formed of 
Upper Chalk resting on the Chalk Rock, while the outcrop of the 
Middle Chalk is restricted to the slope of the escarpment and to a 
couple of narrow inkers, one south of Childrev Warren, and the 
other at the head of the Ilslev Valiev. 
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South-east of Chilton the escarpment is traversed by the valley 
of an old river-course, and the area occupied by the Middle Chalk 
here widens out again and forms the triangular plateau marked 
on the older Ordnance map as Blewherry Plain. Thence it passes 
round Blewberry Hill and trends south-eastward into the valley of 
the Thames, but running up into the long combes which open east¬ 
ward toward Moulsford and Streatley. 
The two zones of the Middle Chalk in Berkshire have a combined 
thickness of about 150 feet, of which the lower 50 or 60 feet may 
lie referred to the Rhynchonella Cuvieri zone. 
Stratigraphical Details. 
The chalk of the Terebratulina zone is exposed in the pathway 
west of the "Horse” on Whitehorse Hill, and consists of firm white 
chalk with a few small finger-shaped flints. Lower down there is 
hard chalk with much Inoceramus- shell, but its base is obscured. 
The Melbourn Rock, however, is exposed in the upper pit on Blow¬ 
ing stone Hill, which shows— 
feet. 
Hard nodular chalk 10 
Very hard nodular rock, mottled with greenish-grey, seen for 4 
There is a marked plane of division at the top of this massive rock- 
bed, but, though the Lower Chalk was exposed at the entrance to 
the quarry, the thickness of the rock could not be ascertained. 
