JST. 67.] HYDRO-GEOLOGICAL MAP. 297 



He was to see what could be done by some of the City people. 

 I hope to be at the next meeting of the Society, and will hear 

 what Karnsay and others say. 



I, however, do not think with you that the line between 

 Meux's and Kentish Town is the best place for a trial. These 

 Devonian strata roll so much that I should give them a wide 

 berth. Kentish Town may be the central axis, and the coal 

 strata lie a few miles north of it. This new well of the New 

 Eiver Co. will throw some light on the subject. Mrs Prestwich 

 joins me in kind regards and best wishes for the New Year to 

 you and yours ; and I am, ever sincerely yours, 



JOSEPH PRESTWICH. 



A final effort was made for the publication of his 

 Water Maps, as shown in the annexed letter, but his 

 application was unsuccessful. 



J. Prestwich to the Duke of Richmond and Gordon. 



OXFORD, 6th May 1879. 



MY LORD DUKE, May I be allowed to recall to your re- 

 collection the circumstance of my having drawn up, at the wish 

 of the other members of the Water Commission, on which I had 

 the honour to serve under you, a hydro-geological map of the 

 Thames Basin for the purpose of showing the extent of the per- 

 meable and impermeable strata and the position of all the prin- 

 cipal springs. To these were added contour lines laid down by 

 the late Sir H. James to mark the height of the springs and of 

 the rivers in the different parts of their course. This map was 

 accompanied by a plate of sections showing the dimensions of 

 the underground reservoirs furnishing the springs, which, with 

 the direct flow of the rainfall from off the impermeable strata, 

 gives the total quantities of water available for the supply of 

 London and other towns in the Thames Basin. 



The map and sections were engraved, and, as I understood, the 

 necessary number of copies was actually struck off, but owing to 

 some cause, of which I believe the cost of colouring was one, 

 they were never completed and put into circulation, with the 



