INTRODUCTION.: XVii 
Middle Oolites. The Oxford Clay, a thick blue clay 
weathering on the surface to yellow, commences in the form of 
a low ridge of wet ground rising above the flat surface of 
Cornbrash, and covers a broad tract of the county from 
Lechlade, by Bampton, Ducklington, South Leigh, Yarnton, 
Hampton Poyle, the dreary flat of Otmoor, to the Bucks border, 
forming remarkably dull and unpicturesque country. Outliers 
occur at Wilcote, Ramsden Heath, Coombe, Tackley Heath, 
and Kirtlington; everywhere it forms a cold stiff land difficult 
to cultivate and often under pasture. The London and North 
Western line from Bletchley passes almost entirely over this 
formation, and passengers by it obtain little idea of the varied 
and beautiful character of much of the Oxfordshire scenery. 
Near Oxford the clay is about 600 feet thick. Gryphea dilatata is 
a typical fossil. The surface of the clay is rendered less heavy- 
and dull by a thick deposit of Drift, the Wychwood outliers 
being capped with a high level quartzose gravel reaching an 
elevation of 500 feet. To this gravel deposit we owe the oc- 
currence of several ericetal plants and its juncture with the clay 
is shown by some springs which still yield Sphagnum and a 
few uliginal plants. Tackley Heath is also covered with gravel 
drift, on which Rosa spinosissima occurs, and North Leigh is 
similarly formed, but in this case Ulex Gallii, Calluna, Sagina 
nodosa are the plants we owe to it, the clay underneath 
holding up the water and thus giving a home for Eleogiton 
fluitans and Peplis portula. The common plants of the Oxford 
Clay are Senecio tenuiflorus, Picris echioides, Juncus glaucus ; 
Mentha piperita, Stellaria palustris, Rumew maritimus being 
confined to it or to the alluvium with which it is covered. 
Lower Caleareous Grit forms a layer about 70 feet thick, 
and consists of yellow sands occasionally bound together by 
a calcareous cement and very changeable in character. In. 
Berkshire it is found on Wytham Hill and in Oxfordshire ‘it 
forms a tabulated area on which are built Headington, Elsfield, 
Beckley, and Stanton St. John;’ and although this attains no 
great height, very extensive views over the Clay and Cornbrash, 
districts of Oxfordshire may be obtained from the summit of 
the northern escarpment. Turritis glabra, Vicia lathyroides are. 
found on it, and the small valleys which flow from the northern, 
b 
