NATURE 



329 



THURSDAY, FEBRUARY 7, \i 



JURASSIC ROCKS UNDER LONDON 



ON two previous occasions ' the attention of the readers 

 of Nature has been directed to the facts which 

 have been revealed by deep borings in search of water 

 under London. In the first of these communications it 

 was shown how completely the predictions of geologists, 

 as to the nature, succession, and thicknesses of the dif- 

 ferent strata under London had been verified ; and in the 

 second the question of the possibility of finding workable 

 coal-seams beneath the metropolitan area was discussed 

 at some length. 



Quite recently, however, a new boring has been put 

 down within the London Basin, which has made known 

 so many new facts of surpassing interest to the geologist, 

 and has at the same time furnished them with new data, 

 tending to modify their former conclusions on some im- 

 portant problems, that it may be well to recur to the 

 subject in the pages of this journal, and to give a short 

 account of these remarkable discoveries. 



The growing wants of the town of Richmond in Surrey 

 have caused the local authorities of that place to seek an 

 augmentation of their water-supply by carrying to a much 

 greater depth a well which had some years ago been put 

 down into the Chalk. This has been done by boring by 

 Mather and Piatt's flat-rope system, the work being done 

 under the direction of Mr. C. Homersham, C.E., and at the 

 present time a depth of 130S feet has been attained. Not 

 only is this well actually a few feet deeper than the famous 

 well at Kentish Town, which was carried 1 302 feet beneath 

 the surface, but, commencing as it does near the level of 

 the Thames, it reaches, reckoning from the Ordnance 

 datum line, a level more than 150 feet lower than that 

 of any well hitherto sunk within the London Basin. 



Up to the present time only insignificant supplies of 

 water have been obtained, but it is to be hoped that as 

 the work is carried on this spirited enterprise may meet 

 with the success it so well deserves. To the student of 

 London geology it has already afforded a number of facts 

 of wonderful novelty and interest. 



The succession of strata found in this well was as 

 follows : — 



feet 

 Made ground and gravel 10 



London Clay 1 60 



Woolwich and Reading .Series ... 60 

 Thanet Sand 23J 



- Chalk with flints | 



Grey Chalk \ 671 



Chalk Marl \ 



Upper Greensand 16 



I Gault 201J 



Neocomian (?) lo 



Great Oolite 874 



New Red Sandstone and " Marl " 60 + 

 The lines indicate unconformable breaks in the series 

 of strata, and the lapse of enormous periods of time 

 between the deposition of the beds which they separate. 

 Down to the base of the Gault the order and thick- 



■ See Nature, vol. xvi. p. 2, and vol. xxv. pp. 311, 361. 



Vol. XXIX. — No. 74 



Tertiary, 

 243 i feet 



Cretaceous, 

 8884 feet 



nesses of the several formations was exactly what would 

 be predicted by any geologist conversant with the details 

 of London geology. Some very interesting facts concern- 

 ing the divisions of the Chalk strata under London have, 

 however, been made out for the first time by the study of 

 the admirable series of "cores" brought to the surface 

 during these boring operations. 



But it is with respect to the strata found lying beneath 

 the Gault that the greatest amount of interest has been 

 excited among geologists. 



The Gault clay has at its base the usual band of phos- 

 phatic nodules, the so-called " coprolites," and beneath 

 this was found a series of beds, ten feet in thickness, the 

 nature of which is peculiar, while their age is somewhat 

 probleinatical. 



These beds appear in fact to consist of materials derived 

 from the wearing away of the rocks on which they repose, 

 but include fragments of other rocks evidently brought 

 from a distance. They contain many " derived fossils," 

 greatly fractured and waterworn, but very few of its 

 organic remains are of the age of the deposit itself, 

 and serve to fix its geological age. From a considera- 

 tion of the whole of the evidence in this case, how- 

 ever, this series of rocks, ten feet in thickness, may be 

 referred with considerable probability to some part of the 

 Neocomian period. Unfortunately the typical Lower 

 Greensand was wholly wanting, and the expected supplies 

 of water from this source were therefore missed. 



But immediately beneath this peculiar and somewhat 

 puzzHng stratum, deposits of great interest to the geologist 

 were encountered. They consisted of thick beds of oolitic 

 limestone, with some subordinate beds of clay, fuller's 

 earth, and sandstone, the whole having a thickness of 

 87i feet. A few fossils, for the most part very imperfect, 

 were found in the limestone, but one of the clay bands, 

 when carefully washed, proved to be veritable "El Dorado" 

 to the paleontologist. It was seen to be crowded with 

 specimens of Brachiopods, Bryozoa, Echinoderms, and 

 other organisms, all of them in the most exquisite state 

 of preservation. It is evident that these organisms which 

 flourished upon the floor of the sea were killed and over- 

 whelmed by a sudden influx of muddy sediment. The 

 species found in this interesting bed of clay, which is only 

 six inches in thickness, are similar to those which occur 

 in the Bradford Clay of Wiltshire, and the Calcaire de 

 Ranville of Normandy. It is evident, therefore, that the 

 deposit which contains them is of the age of the Great 

 Oolite. These great oolite strata are found to rest directly 

 on the Trias,— the Inferior Oolite, Lias, and Rhaetic being 

 absent. 



Now no strata of the age of the Lower Oohtes were 

 before known to exist under the London Basin, though it 

 is but fair to remember that Mr. Godwin-Austen, in his 

 celebrated essay on the probable existence of coal under 

 London, distinctly pointed out the possibility of the exist- 

 ence of such deposits. 



In the boring which in the year 1878 was put down at 

 Messrs. Meux's Brewery in the Tottenham Court Road 

 some anomalous strata about 64 feet in thickness -were 

 found lying between the Gault Clay and the Devonian 

 rocks in which that boring terminated. From some 

 obscure casts of fossih detected in these beds, they were, 

 at the time of their discovery, referred to the Neocomian. 



Q 



