New Well at Addington. 153 



no lining. Several tunnels 6 ft. high by 4^ ft. wide have l)een 

 driven from the well, the longest, at a depth of 142 ft. from the 

 surface, 291 yards in a south-easterly direction. From this a 

 branch heading at a distance of ten yards from the well has been 

 excavated for a length of 156 yards to the northeast, and from 

 this again two other branches extend in a south-easterly direction 

 imrallel with the long main heading. The lowest heading is 

 153 ft. from the surface, and is 62 yards long. 



A guide-pipe for future boring is sunk in the bottom of the 

 well. Bore-holes have been pierced at certain places at the sides 

 of the headings, some of which yielded water. The well is sunk 

 entirely in the Chalk, there being no newer deposits overlying it 

 at this spot. Nearly a mile northwards the Chalk dips under 

 the Tertiary Beds (Thanet Sand, Woolwich Beds, and Oldhaven 

 Beds), and these again dip under the London Clay about three 

 miles further north. Southwards the Chalk rises gradually, 

 almost following the inclination of its dip, and about 5^ miles 

 somewhat east of south the Upper Greensaud crops out at a 

 higher level above the sea than the mouth of the well ; but it is 

 about 340 ft. below sea-level at the site of the well. The Chalk 

 excavated from the well contained few fossils, and varied much 

 in density and character. The upper portion was divided by 

 bands of flint, which in some cases assumed the tabular form so 

 well shown in the cliffs at St. Margaret's, near Dover, and 

 resembling the Chert bands in the Portland Beds of the Oolite. 

 The last bed of flints was met with at 152 ft. from the surface, 

 at which depth the Chalk was without fissures, dense, and dry. 

 In excavating the headings numerous water-bearing fissures were 

 cut ; and at 230 ft. from the main shaft, in an easterly direction, 

 a fault was encountered, of which the faces of the Chalk exhibited 

 in a marked degree the striated and grooved appearance known 

 as slikensides. The fissures in several instances contained 

 brown argillaceous matter, probably introduced in part by per- 

 colation from the surface of the ground, and in part due to the 

 dissolving action of water on the Chalk leaving the insoluble 

 clayey matter behind. Below the Chalk at this spot comes the 

 Upper Greensand, essentially a sandstone in this district, of 

 limited thickness. 



As regards the thickness of the Cretaceous strata, probably not 

 less than 50 ft. of higher beds have been removed by denudation. 

 There is some uncertainty as to the total thickness of the Chalk 

 near Croydon. Under London it is about 650 ft., there being 

 but little variation in the sections of deep-well borings. There- 

 fore it is believed that there exists another 400 or 450 ft. of 

 Chalk below the present bottom of the well. As regards the 

 Upper Greensand, 50 ft. would be a liberal allowance, that 

 formation thinning northwards from its outcrop. The Gault 



