DISCUSSION ON WATER-SUPPLY FROM WELLS
Minutes of the Proceedings of the Institution of Civil Engineers
said he thought the diagrams (Figs. 5, G and 7, pp. 12, 16 and 19) had not been sufficient,ly explained. I n each case the lines generally represented pumpiug a t a uniform rate. That, of course, was necessary to obtain a line which represented the actual power or force of the spring. In the case of Rickmansworth (Fig. 7) , at the lower half, the line coming down showed an increase in the rate of pumping. The pumping was generally carried on at the rate of 15,000 gallons, and then it increased
... then it increased to over 21,000 gallons an hour. The diagram showed the value of increasing the depth and the size of the bore-hole. At Wokingham, the spring continued to fall for a number of hours : in ten hours it had fallen 42 feet, then, on ceasing t o pump, it rose for many hours, but not to its original level. That showed that the water had great difficulty in reaching the borehole, due to the fact that it had to travel a great distance underground. The water was coming on as fast as it could, but it could not get through in consequence of the enormous pressure of the Tertiary beds overhead. The thing t o be sought for in chalkwells was the presence of flints. Wherever there were flints in abundance there was water in abundance, and where there were no flints there was little water. He had often had the idea that the water itself tended to create the flint in chalk, but how far that theory was to be supported by chemists and geologists he did not know. What happened was this :-In flint beds in the Chalk there was a quantity of sand ; and on pumping, that sand gradually worked out, the water dissolving the Chalk and leaving spaces between the flints, through which it could readily travel. In the case of the Leatherhead well, a t t h e bottom there was a continuous bed of flints, hence a vast underground reservoir of water. It was Minutes of the Proceedings of the Institution of Civil Engineers 1887.90:40-90.