Vol. 62.~\ PHOSPHATIC CHALKS OF WIXTEEEOF/EXE AXD BOXFOED. 501 



strata in a Phosphatic-Chalk group not less interesting than that of 

 Taplow. 



The principal observations made in the course of this investi- 

 gation are recorded in the following pages. 



The piece of country with which we are chiefly concerned forms 

 part of an irregular, southward-pointing spur, or inter-vale, lying 

 in the angle between the convergent valleys of the Lambourn and 

 the Winterbourne, and further defined, on the west, by the dry 

 combe of Hangman-stone Lane, which joins the Lambourn Valley 

 at Boxford. The crest of this spur stands between 150 and 180 feet 

 above the floors of the rather sharply-incised valleys just mentioned, 

 and, although somewhat ' accidented ' near its southern end, rises 

 persistently northwards, and eventually merges into the general 

 dip-slope of the Berkshire Downs. 



The common boundary of the parishes of Winterbourne and Box- 

 ford traverses the spur longitudinally, keeping somewhat to the 

 east of the line of highest ground. Xear Winterbourne village 

 this ' 'tween-stream ' block consists of Upper Chalk surmounted by 

 outlying masses of sandy and clayey Eocene (Beading) strata, the 

 largest and thickest of which outliers forms the rounded eminence 

 of Borough Hill, and the gravel-capped plateau of Basford Hill to 

 the south of it. The prevailing dip of the Chalk and Eocene deposits 

 hereabouts is a gentle one to the south-east, but there are local and 

 discordant dips in the Chalk — some of considerable strength — 

 which are not shared, by the newer strata. 



The several exposures of Phosphatic and other Chalks about to be 

 described or noticed are indicated in the accompanying sketch-map 

 (fig. 1, p. 500) by the letters (a) to (w). These will be dealt with in 

 alphabetical order, but in two groups : those from (a) to (e) inclu- 

 sive falling under the heading of AVinterbourne exposures ; and 

 the remainder under that of Boxford exposures. 



IT. Exposures ix the Paeish of Wixterbotjrne. 



(a) Pit a quarter of a mile north- west of 

 Winterbourne Church. 



Originally this pit had a maximum depth of 15 feet, but the 

 talus has now mounted halfway up the face. The disposition of 

 the principal lithological divisions seen on its southern side, and in 

 a trial-hole opened by us in its floor, is shown in fig. 2 (p. 502). 

 The dip is about 3°, to the south-west, or nearly so. 



Commencing at the bottom : — The chalk in the trial-hole is white, 

 wdth scattered brown granules, and is, for the most part, friable, 

 coarse-grained, and harsh to the touch, but contains firm to hard 

 lumps without definite shape or limits. Obscure branching bodies 

 of slightly-greyish tint and of coarser texture occur in places, and 

 small hard nodules (measuring up to a third of an inch in diameter), 



