72 METROPOLITAN DRAINAGE. [l849. 



D'Archiac, in his ' Histoire des Progres de la Geologic/ reviews 

 the subject, but does not go very fully into it, nor am I aware 

 that any of the French geologists have more than alluded to it 

 briefly, excepting, however, M. D'Archiac, who has well and 

 frequently discussed it in several of his works. I remain, my 

 dear sir, yours very truly, J. PRESTWICH. 



With reference to the range and thickness of the 

 local Tertiaries, the following is the draft of a letter 

 on the Metropolitan- Main Drainage, addressed to Sir 

 Henry De la Beche : 



20 MARK LANE, Augt. 1849. 



MY DEAR SIR HENRY, In the report of the meeting of the 

 Commissioners of July last several points were raised connected 

 with the geology of part of the neighbourhood of London, 

 especially with that portion of it extending eastward from 

 St Paul's to the marshes opposite Woolwich. The subject was 

 discussed in connection with the question of Mr Phillips's tunnel 

 scheme, on which it has no doubt an important bearing. As 

 considerable doubt seemed to exist as to the extent of the range 

 of the London Clay and its depth through Eastern London, 

 and also as to the nature of the beds between the London 

 Clay and the Chalk, I venture to take the liberty of communi- 

 cating the few facts I am in possession of connected with the 

 geology of the district. As I believe a series of borings is 

 in the course of execution, the observations may probably be 

 of no use, and it will be unnecessary to bring them forward. 

 If, however, they should tend to throw light upon any one 

 doubtful point, it will give me much pleasure, and I beg you 

 will make any use of them you think fit. 



The consideration of t^his question geologically has led me 

 to examine with some attention the various plans proposed 

 for the more efficient drainage of London, and at the risk of 

 being probably thought by you very presumptuous in venturing 

 to give an opinion upon such a subject, I have in paper "B" 

 expressed some difficulties I cannot but foresee in Mr Phillips's 

 plan, and have given a sketch of a plan which might possibly 

 obviate some of them. I may be all wrong if so, burn the 



