916 C. MOOltK OK THE PALJ30NX0L0GY 



beds have been met with elsewhere in any of the Cretaceous outcrops ; 

 but possibly, like the Great Oolite, they may not have been continu- 

 ous over a large area. Their presence shows an interruption or 

 change of deposition from some physical cause, and probably inter- 

 vals of time between succeeding beds. 



There are only two sources from which to obtain any evidence 

 regarding the jmysical conditions which prevailed under London, as 

 revealed by the Meux well-boring : — first, from the petrology of the 

 materials passed through ; and, secondly, from a study of their or- 

 ganic contents. Beyond their palceontologj^, I have nothing to 

 remark in the beds from the Gault upwards. 



As regards the first head, the deposits from about 1000 feet down- 

 wards to the Devonian shales have been very properly decided to re- 

 present one of the periods of the Lower Greensand ; but it belies its 

 name, for it is throughout entirely calcareous. I have been unable 

 to trace any distinct line of stratification or bedding therein. It 

 puts on the look of a roughly granular or slightly conglomeratic 

 marl, such as might have been deposited in hollows or basins, and 

 subject to the influence of currents of water passing over it, whereby 

 it would be again disturbed and redeposited. It is grey in colour, 

 with a slight blue tint, caused by an admixture of the debris of a 

 darker bed, which I at first thought was phosphate of lime or chlo- 

 ritic grains, but which, like the rest of the deposit, proved to be cal- 

 careous. A familiar comparison for the deposit between the Gault 

 and the Devonian would be that of coarse dried builder's mortar. 

 Its lithological aspect led me to anticipate that there would surely be 

 mixed up with it some records from the long interval between the 

 Cretaceous and the Palaeozoic periods ; but with the following excep- 

 tions, one of which is of some interest, my examination for derived 

 material was unsuccessful. Even the surface of the Devonian beds 

 seems to have been so thoroughly cleansed of loose matter of its own 

 age before the deposition of the Neocomian deposits above, that not 

 a grain could be detected mixed therewith. The specimens which, 

 from their character, I have little doubt are derived, are some small 

 irony-looking grains of quartz, several grains of what appear to be 

 sulphate of barytes, a minuto flake of carbonate of copper, and 

 several small grains of coal. Regarding the latter, it was not to be 

 expected that the borer would be fortunate enough to pass through 

 an erratic boulder of coal like that found in the Chalk near Dover 

 some time since, nor would there be any need ; for however small the 

 fragments, they equally imply the possibility of coal somewhere in 

 the district. It is much to be regretted that other confirmatory evi- 

 dence could not be obtained on this point. Whence these fragments 

 come, whether from true Carboniferous beds present along the 

 Paleozoic anticlinal, or from Secondary deposits like those mentioned 

 by Professor Judd, in Quart. Journ. Geo! Soc. 1871-3, as occurring 

 in Spain in beds which in time may be represented by those in the 

 Meux well, must be a matter for conjecture. 



