BENEATH THE LONDON CLAY. 151 



a drinking water, absolutely free (unless our well has been badly 

 constructed, so as not to exclude all other waters) from organic 

 impurity, and, unless we are unfortunate in our locality, as I 

 believe here we should not be, having so small an amount of 

 hardness as to be properly classed as a soft water. We may, 

 however, be unfortunate, and find that the water, while it 

 possesses every other merit, is excessively and stubbornly hard, 

 and then woe to the unfortunate water company which has sunk 

 the well and its directors, if the clients whom they supply find 

 their domestic boilers and hot-water services continually furred 

 up, and there is a neighbouring company ready to invade their 

 district with a water which, if not so good in some respects, has 

 not this conspicuous demerit. I speak feelingly as a former 

 director of the Harrow Water Company which is now extinct, 

 having been thus unfortunate and therefore extinguished after the 

 fashion at which I have hinted. It was from our efforts to deal 

 with this stubborn water that I was led to turn my attention to 

 the questions I am now attempting to discuss. 



When the well is finished, the water (when pumping is not 

 going on) would probably, at this date, be found to stand in the 

 well just about up to the Ordnance Datum Level, or level of the 

 sea; that is, since the top of the chalk is here about i8o feet 

 below the O.D., it would stand about i8o feet above the top of 

 the chalk, and nearly at the same depth below the surface of the 

 ground. This shows that the spring of water which we have 

 tapped is under a pressure of considerably more than that of a 

 column of water i8o feet high. The quantity of water which 

 would be obtainable for distribution from the well would be rather 

 limited by the power of the pumps than by the capacity of the 

 well — at any rate, up to a million gallons per day, and probably 

 considerably beyond. 



If we now enquire whence all this water comes originally, we 

 shall find that, like all other sources of water supply, it is to be 

 traced to the rain which has descended from the clouds, though it 

 has had a long underground journey since it left the light of day. 

 The geological structure of the Thames Basin, of which Middlesex 

 forms a part, is (so far, at least, as we are concerned with it here) 

 very simple. Every one who travels, with his eyes only half 



