42 
POPULAR SCIENCE REVIEW. 
Wealden Boring has as yet thrown no certain light on this 
question. A decided negative result there will not prove the 
absence of coal measures under London, and other trials will 
one day he made in this direction. Wild as this surmise may 
seem, it is one worth considering as regards this question. 
The following table exhibits the amount of spring water 
available within the Thames basin, including the supply avail- 
able from wells of the existing companies : — 
Gallons per day. 
Springs and wells of the New Biver Company . . . 12,000,000 
Wells of the Kent Waterworks Company .... 15,000,000 
Chalk springs at Grays 10,000,000 
„ „ between Lewisham and Gravesend * . . 43,000,000 
„ „ above London 30,000,000 
Total from the chalk .... 110,000,000 
Lower Greensand district of Leith Hill, Hinahead, &c.f . 20,000,000 
Oolitic springs on the N. side of the Thames J 70,000,000 
Total . . 200,000,000 
These estimates are independent of the Bagshot district, and 
the lower greensand range from Bedhill to Maidstone. The 
supply might be largely increased by additional wells sunk in 
the chalk, lower greensand, and oolites. A large quantity of 
water might be obtained by sinking near the Cotteswolds Hills, 
through the inferior oolite to the Midford sands; this, how- 
ever, would probably rob the Severn of its spring water, which 
now flows out on the western side of the Cotteswolds. 
It is thus evident that sufficient pure water can be obtained 
within a moderate distance of London ; sufficient even for the 
entire future consumption. To bring water from so many 
sources will certainly be expensive — perhaps as much so as the 
most costly scheme for far-distant sources. But the expense can 
be incurred gradually ; the nearer sources may be taken first, 
those further off at later times, as the demand increases. 
If the supply for domestic use can be separated from that for 
general purposes, an enormous saving of good water would 
probably be valuable as regards our knowledge of the range of the older 
rocks. I may here remark that the description which I gave of the Sub- 
Wealden Boring in a previous number of this Review (vol. xiii. p. 399) 
requires some modification. A second boring, carried to a depth of 1,820 
feet, has proved that the Kimeridge clay extends to 1,750 feet at least. 
* Mr. Barlow estimated sixty millions from this source. 
t Estimates of the yield of this district vary greatly. I take less than 
the lowest. 
% River Pollution Commission, Sixth Report, p. 297. This is the 
estimated summer yield of only twelve springs. 
