THE JURASSIC DEPOSITS WHICH UNDERLIE LONDON. (ag 
metropolis have since demonstrated, the great water-bearing deposit 
of the Lower Greensand does not occur under London itself, the Gault 
there resting on lower members of the Mesozoic series or directly 
upon Paleozoic rocks. 
But although the hope of finding the Lower Greensand as an 
abundant source of water-supply immediately under London had to 
be abandoned, it nevertheless seemed possible that this important 
water-bearing stratum might be tapped by Artesian wells at places 
sufficiently near to the metropolis to supplement to a great extent, 
if not altogether to supersede, the use of the waters of the Thames 
for drinking-purposes. The thickness of the Lower Greensand at 
its outcrop in Surrey and Kent, the very pervious character of its 
beds, and its steady dip under the Chalk, pointed to the probability 
that at places within the ever-growing area of the metropolis, as at 
Sydenham or Croydon, such sources of water-supply might be 
easily reached *. 
The discovery of a considerable thickness of what were supposed 
to be strata of Neocomian age, though of somewhat anomalous 
character, so far northward as the site of Meux’s Brewery led to 
the anticipation that the more normal condition of the Upper 
Neocomian would be met with at no great distance, and that in the 
southern part of the London area Artesian wells might be put down 
into the pervious Lower Greensand. 
The facts which have been described in the present paper, however, 
show that the 64 ft. of oolitic limestone at Meux’s Brewery are of 
Jurassic, and not of Neocomian age, and that as far southwards as 
Richmond there is no trace of the normal type of the “ Lower 
Greensand” strata. 
The deposit which does probably represent the Upper Neocomian 
at Richmond is of a very peculiar character, resembling in fact the 
“ Tourtia,” which in Belgium separates the rocks of Paleozoic age 
from the overlying Chalk. In both cases the rock is made up of 
reconstructed and derived materials. This peculiar deposit at 
Richmond is less than ten feet in thickness ; from its nature it can 
scarcely be expected to form a regular and widespread bed, and it does 
not yield any supply of water. It would be of much interest if a 
deep well were put down at Croydon, to prove whether the normal 
condition of the strata of Lower-Greensand age is maintained so far 
to the northward as that town. The possibility of finding large 
supplies of excellent water ought to be a sufficient inducement for 
the undertaking of this interesting experiment. 
The Oolitic strata at Meux’s Brewery and at Richmond have 
unfortunately proved useless as sources of water-supply. . 
But the discovery at Richmond of beds which are certainly of a 
somewhat pervious character, and are apparently of Poikilitic age, 
suggests the possibility, though I fear I cannot add the probability, 
of finding water there; and this suggestion receives some support 
from the fact that, after the red rocks were reached, small but * 
* See Prof. Prestwich’s Anniversary Address to the Geol. Soc. 1872 (Quart. 
Journ. Geol. Soe. vol. xxviii. p. 1x). 
Q.J.G.8. No. 160. 38 
