150 ON THE WATER IN THE CHALK 



now reach. This series of strata is known as the ^^^oohvich and 

 Reading beds, from the places where they appear close to the 

 surface. From one, if not all of the beds of sand, we should almost 

 certainly find a considerable quantity of water pouring into our 

 shaft, but it is not the water of which we are in search, as, besides 

 being probably deficient in (quantity, at any rate, after a short 

 period of pumping, it is doubtful whether its quality would be 

 satisfactory for domestic purposes. Our engineer would, there- 

 fore, be careful to exclude it entirely from our well by iron 

 cylinders or other suitable lining. He ought, however, in the 

 interest of science, to take a kw good samples of this water to be 

 handed over to a chemist for analysis. (I speak penitentially, 

 having to reproach myself for not having done this when, a few 

 years ago, a new well was sunk at the Harrow AV^aterworks, 

 having lived to regret the neglected opportunity.) 



I said that we might now find that we had reached the chalk, 

 but we might find a certain thickness of other sands to be ])assed 

 through (as we certainly should farther south), known as " Thanet 

 sands," or " grey sands." It is stated that where the Thanet sands 

 exist below the Reading beds, water is usually found in the lower 

 Thanet sand, and not in the sand of the Reading beds. Also, 

 " that the grey (Thanet) sand contains a highly argillaceous mixture 

 in its lowest part, which serves to isolate it as a water system from 

 that of the chalk " (Lucas). I cannot find distinct evidence as to 

 whether, where the Thanet sand is absent, there is, or is not, separ- 

 ation of the water in the sand above from that in the chalk below 

 by entirely, or almost entirely, impervious clayey beds. Probably 

 there is free communication in some localities, and more or less 

 separation in others. 



Our shaft having reached the chalk, we shall probably continue 

 the well by a borehole from its centre, carried into the compact 

 mass of the chalk, until we obtain a copious supply of water, 

 probably from having tapped some fissure filled with water, which, 

 at this depth, will be under considerable pressure. It may 

 probably be found well to carry this borehole to a depth of loo, or 

 even 200 or 250, feet into the chalk. We shall now have obtained 

 a copious supply of excellent water — bright and sparkling, with a 

 small degree of salinity sufficient to make it brisk and pleasant as 



