758 PROF. J. W. JUDD ON THE NATURE AND RELATIONS OF 
increasing quantities of water, having the high temperature of deep- 
seated sources of supply, rose to, and indeed far above, the surface. 
Although the outcrop of the Poikilitic strata is situated at a 
distance from London not greater than that which separates the 
outcrop of the water-bearing strata from the Artesian wells in 
Paris, yet, considering the whole of the circumstances of the case, I 
cannot regard it as probable that supplies of water will be obtained 
under London through continuous strata of Poikilitie age out- 
cropping at the surface. The variable nature of the Poikilitic 
strata, the doubt of their continuity over a considerable area (a 
doubt strongly suggested by their absence at the Tottenham Court 
Road, Turnford, and Ware wells), and the frequency of salt deposits 
which would vitiate the supply, all tend to destroy the hope of 
obtaining water from the Poikilitic rocks under London. 
But as it is now proved that there exist pervious beds at great 
depths under London, and it is also certain that large supplies of 
water are carried down through the Lower-Greensand formation, 
it is just possible that the pervious strata may be saturated with 
water from other beds which, by overlap or faulting, lie in contact 
with them, and that such water may be made to rise to the surface 
in Artesian wells. 
C. The Possible Eaistence of Coal at Workable Depths under 
London. 
Some years ago I ventured to suggest that the deep borings under 
London had already thrown so much light on the nature and rela- 
tions of the different rocks forming the great Paleozoic ridge, that 
the time had arrived when it was worth while to commence a series 
of systematic trials to the south of London, with a view to solve 
the problems of the presence and position of coal-bearing strata 
within the metropolitan area. I also endeavoured to determine the 
points at which such trial-borings might be most advantageously 
put down *, 
Shortly after the appearance of these articles, M. Ad. Firket, an 
eminent geologist and engineer, published an abstract of the views 
which I had enunciated—in which he generally concurred—in a 
foreign journal, adding some valuable remarks of his own upon the 
subject 7. 
The deep well at Richmond has supplied one more of the desired 
borings running in a line from north to south across the London 
Basin. But it has at the same time afforded new data calculated to 
modify to some extent the conclusions at which geologists had pre- 
viously arrived. These I shall proceed to discuss. 
From the facts detailed in this paper it is now evident that, in 
the southern part of the metropolitan area, shafts in search of coal 
would probably have to be carried through a considerable thickness 
of Oolitic strata, and that these Oolitic strata probably increase in 
* Nature, vol. xxv. pp. 311 and 361. 
t Revue Universelle des Mines &c. tome xii. 2° série (1882), p. 407. 
