OF THE BAGSHOT BEDS OF THE LONDON BASIN. 173 



these sands are seen as clean fine quartz-sand, finely current- 

 bedded, and overlain by the irony loam which often occurs at 

 the base of 'No. 10, from the admixture of clay material with 

 the sands next below. No. 10 can be traced in ditch-sections a 

 good way to the west towards Longmoor, an extensive lake-basin 

 dug partly in London Clay, just below the 200-foot contour. 

 Near this a well at a higher level gave the following : — 



Section R. Well at Longmoor, Finchampstead. 



feet. 



a. Gravelly drift 1 



b. Soft loamy particoloured clay (laminated), " like | o /_ -^ iqn 



that dug at California, but not quite so strong "J ^"^ * ^' 



c. Soft loose sand 12 (= No. 11). 



16 



Bed No. 10 is seen in a road-cutting on Nine-mile Ride, above 

 the 200-foot contour, three-quarters of a mile west of California ; 

 and at another three-quarters of a mile west we come to the end 

 of Nine-mile Eide, where London Clay is dug at 185' O.D. 



Western Spur of The Bidges. {The Church Hill.) — As this hill 

 presents some rather puzzling points of structure, I may be 

 excused for going more into details here. 



1. By the levels of the new six-inch Map of the Ordnance 

 Survey*, the highest point of this hill is 330 feet above O.D. 

 The Upper Sands which cap this hill appear to be a continuation 

 of those of The Bidges, not an outlier of them, as mapped by the 

 Geological Survey. 



2. A pebble-bed (2 feet thick) at the base of these sands is 

 exposed, at 300' O.D., at the first turn of the road behind the 

 White Horse Inn and north of the church. It was proved 

 (1^ foot thick) at 280' O.D., 500 yards south-east of this point, 

 by excavations made for me in the roadside, giving a dip S.E. of 

 1 in Tlf, or rather less than 1°. In both cases the pebbles are 

 imbedded in clay, and the underlying bed is clay. In The Bidges 

 the clay of No. 5 seems generally to thicken and cut out the 

 loamy sands of bed No. 4 of the College sections. 



3. The lane turns sharply north of west from the above-men- 

 tioned* point for 120 yards and descends 20 feet (as determined by 

 levelling) to the small alder- swamp, fed by springs evidently 

 from the base of the Upper Sands. This gives a dip of about 

 1 in 17^ {i. e. from 3° to 4°) in this direction. 



4. From this point the lane runs due west on these clays along 

 the hill-flank for nearly 300 yards (showing absence of any 



* The discovery of a discrepancy of some 20 feet in the levels around the 

 crest of this hill as they are given on the older and the newer six-inch maps 

 has necessitated the re-writing of this portion of the paper after communica- 

 tion with the Director of the Ordnance Survey, whose courtesy I have the 

 pleasure of acknowledging here. 



t Correcting this for the true dip, presumably towards the Blackwater, we 

 get about 1 in 50, or rather more than 1°. 



