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Rh quantity on Westbury Wild, where the soil is a stiff clay, but I suspect a strong Calcareous element is present. The scenery of the Great Oolite district is much more diversified than that of the clay ; it is often well wooded, and the ash is a conspicuous tree. One of the members of the oolitic rocks, the Forest Marble, gives in Oxfordshire a home for some of the chief rarities of the county, but this formation is only scantily repre- sented in Buckinghamshire and chiefly near Thornton, Lillingstone Lovell and Tingewick, and so far as I am aware without influencing the vegetation. The Cornbrash is found in a more or less continuous band from Fringford near the Oxfordshire border across the county to Newton Blossomville on the eastern side ; it is nearly obscured by the Ouse gravels east of Newport Pagnell, but near Beachampton it is two miles across. This formation, which is well represented in Oxfordshire, consists of various rubbly limestones sometimes, as near Buckingham, of a hard blue character and associated with beds of blue and black clay, but the limestone weathers rather rapidly, and in some of the quarries, as at Thornborough, one can notice that the base consists of blue limestone alone, but as the surface is reached the top beds are yellow and rubbly, and this colour change is owing to the oxidation of the iron carbonate which is present in the older and lower rock, it being gradually altered by air and moisture into oxides of iron near the surface. There is a curious inlier of Cornbrash at Marsh Gibbon in which we have a blue limestone at the base, then a marly clay capped with loose rubbly stone. This slight eminence is one of a series of similar ones which cross a part of north Oxfordshire as an anticlinal line stretching from west to east, and although not much raised above the plain of Oxford Clay in which they occur, yet these dome shaped masses have been occupied by villages in each case. As a rule the arable land on the Cornbrash is of a deep reddish-brown colour and is well adapted for the growth of wheat, but it produces few characteristic plants and the outline of the surface is also somewhat featureless. On the village walls made of the local stone at Marsh Gibbon, the stone crop (Sedum dasyphylluni) grows in one of its very few homes in the county.

The Oxford Clay so frequently referred to is a light-blue clay weathering to yellow on the surface and of a great thickness, in many places being over 500 feet. It occupies a considerable area of the north of the county, forming a more or less undulating surface, uninteresting from a scenic point of view, and without an attractive flora. From the absence of springs, and from its impervious soil, there are fewer villages on it, and it therefore is a sparsely populated area, so that the plants which follow man and his operations are necessarily fewer ; but the new industry of brick-making will probably introduce some species. The contrast between its common constituents and those of the oolitic rocks has been already alluded to, but as the Ouse has excavated into it for a considerable portion of its course, the aquatic vegetation is the most marked in character. Near Stoney Stratford the sweet flag ( Acorus