INTRODUCTION llx 



it crosses, and a half-mile beyond reaches the Ridge Road, which is 

 then taken as the boundary between the Ock district and the Kennet 

 valley, since it is practically the watershed, running as it does along 

 the top of the Chalk escarpment all the way to the Wiltshire border. 



It has already been stated that the Ock district bears a very notice- 

 able relation to the Thame district of my Flora of Oxfordshire, not only 

 in its geological character, but also on account of its scenery and 

 botanical features. The Oxfordshire high ground of Shotover has its 

 counterpart in Berkshire in the Boar's Hill range, and that range, 

 though slightly lower, is richer in its vegetation. The Oxfordshire 

 Chalk hills, which at Beacon Hill rise to 809 feet above the sea, are 

 overtopped by the White Horse Hill, which attains a height of 

 840 feet ; but the Berkshire Chalk escarpment, though rather higher 

 and perhaps steeper than the Oxfordshire range, is not so well wooded 

 nor so varied in outline. 



The river Ock drains the larger portion of the district, the vale part 

 of which is excavated in the Kimeridge Clay. It is a stream with 

 many head-waters, several of which sj^ring from the junction of the 

 Chalk and the Gault, as at Compton Beauchamp, with its moated 

 house, at the foot of the White Horse Hill near Ufifington, at Kingstone 

 Lisle, Letcombe, and Childrey, where there is one of the largest holly- 

 trees in England. In fact, just as the sites of many villages in Oxford- 

 shire at the base of the Chalk escarpment were chosen on account of 

 the presence of springs of clear pure water, so here under similar 

 circumstances we have the same effect produced. The bare Chalk 

 slopes were rejected, while the sheltered spots with water-springs 

 were selected by the early inhabitants, and villages grew up around 

 them : the streams from these springs, which issue at the junction of 

 the Chalk and Gault at about 460 feet elevation, flow at first bright 

 and sparkling and produce abundance of watercress, but their water 

 becomes muddy later on when they enter on the clay of the central 

 part of the vale. One of the smaller tributaries of the Ock rises on 

 the western side of the county from the greensand of Little Coxwell ', 

 winds round Longcott Hill, and entering the Kimeridge Clay runs by 

 Stanford-in-the-Vale, near a Roman station, at the junction of the 

 Clay with the Coralline Oolite, to Cliarney Basset, where the adjoining 

 meadows are of alluvial formation, and passes thence by the Early 

 English church of Lyford, and by Garford to Marcham, where the 

 meadows are of a very interesting character ; from Marcham to 

 Abingdon the Ock runs close to the Wilts and Berks Canal, in which 

 Potamogeton praelongus is abundant, and P. compressum, Linn, {zosterae- 

 folius;, P. Friesii, P. crispum, P. interruptus, P. pectinatum, P. nutans 



1 At Great Coxwell there is a large barn, 148 feet long, which was built by 

 the Abbot of Beaulieu. 



