1855.] PRESTWICH — BORING AT KENTISH TOWN. 7 



I was led to anticipate a water-supply proportionately larger, and 

 capable of rising through Artesian wells to a height of 1 00 feet or 

 more above the level of the Thames at London*. 



The practicability of such a work was proved a few years since in 

 France by the Artesian well of Grenelle at Paris, which, after traversing 

 148 feet of Tertiary strata, and 1394 feet of Chalk, reached the 

 Lower Greensand, and from this source a large and well-maintained 

 supply of excellent water has since been continually flowing, and 

 rises 130 feet above the sufface. There are several such wells 

 through the Chalk at Tours, Elijoeuf, and elsewhere, some for private^ 

 and others for town supplies, and the greater number are perfectly 

 successful. In London the conditions for a work of this descrip- 

 tion appeared even more favourable than in Paris, for the Lower 

 Greensand in England is much thicker than in France, and the out- 

 crop is nearer to London than to Paris and relatively higher. 



The only apparently serious objection urged against such a work 

 here was the thickness of the chalk, which was variously estimated 

 from 1000 to 1/00 feet thick ; but I showed, that, although it had 

 proved to be more than 1000 feet thick at Saffron Walden, it was 

 probably much less at London, for there was reason to believe 

 that the upper beds of the chalk had been extensively denuded, as 

 they trended towards the area of the Weald, before the Tertiary period, 

 and that the chalk with flints around London, which it had been 

 customary to call the Upper Chalk, belonged in reality to the Middle 

 Chalk. Taking the mean of several sections drawn through Lon- 

 don, I concluded that the chalk would not be found to be more 

 than 600 to 650 feet thick. Adding to this 200 feet as the thick- 

 ness of the superimposed Tertiary strata, which at London vary 

 from 100 to 300 feet, and assigning 40 to 50 feet to the underlying 

 Upper Greensand, and 100 to 150 feet to the Gault, I estimated that 

 the Lower Greensand beneath London might be reached at a depth not 

 exceeding 1000 to 1 100 feet. I suggested that the experiment should 

 be made in low ground, and instanced St. James's Park as a favour- 

 able locality for obtaining by this means natural fountains rising to a 

 considerable height above the surface. 



We are indebted, however, to the Hampstead Water- Works Com- 

 pany for the first attempt to solve this problem practically ; but, as 

 the surface of the ground at their Works at Kentish Town is 1 74 feet 

 above Thames high-water-mark, the situation is not so favourable as 

 might have been wished. A few years since this Company sunk 

 a well through the Tertiary strata (at that spot 324 feet thick), to a 

 depth of 215 feet in the chalk, making a total depth of shaft of 



* I calculated the eflfective area of the Lower Tertiary sands to be 24 square 

 miles, and that of the Lower Greensand 230 square miles ; whilst I estimated the 

 mean thickness of the permeable beds of the former to be 19 feet, and of the 

 latter 200 feet. As it appears that the present water-supply obtained from Arte- 

 sian wells in the Lower Tertiary sands amounts to about 3 to 4 million gallons in 

 the twenty-four hours, I considered it not improbable that from 20,000,000 to 

 30,000,000 gallons might be drawn from the Lower Greensand by means of 

 Artesian wells, without affecting the permanence of the water-level. 



