ON THE CIRCULATION OF UNDERGROUND WATERS. 



399 



The water was then allowed to filter through and drop into the second 

 cube until it passed without any change from the condition of sea water. 

 The second cube, it will be observed, was partially saturated with the 

 filtrate from the first cube, and sea water was added continuously, till it 

 began to drop from the bottom of the second cube, when it was received 

 into bottles and carefully analysed with the results given in the following 

 table, namely : — 



These filtrates are obtained from two cubic feet of sandstone. 



The last drops of the fourteenth filtrate were of the same composition 

 as the sea water, and therefore the filtering power of the stones was ex- 

 hausted. 



In the analyses here given, I dealt only with the chlorides, these being 

 by far the larger and most characteristic constituents of sea water, as 

 will be seen by the following analysis of the sea water used in the ex- 

 periments, namely : — Total solids in one gallon=1505 grains, of which 

 1334-9 grains are chlorides of sodium, magnesium, and calcium. 



Mr. A. Norman Tate, F.C.S., analysed the first, fifth, and thirteenth 

 filtrates, and his analyses agreed to within less than one per cent, with my 

 own as given in the table above, thus proving their substantial accuracy. 

 It follows then that 93-^ fluid ounces of sea water passed through two cubic 

 feet of sandstone before they became inoperative as filters, and nearly the 

 whole of the salts were removed from the water that first passed through. 



Applying this knowledge to account for the water withdrawn from the 

 wells in Liverpool, we should proceed as follows : — The rain water which 

 was stored in the cavities of the rock would be tapped by the wells and 

 bore holes, and pumping would cause a current under great frictional 

 resistance to flow towards the well as a centre from all directions in the 

 surrounding rock. The flowing water, owing to the frictional resistance 

 and capillary attraction of the rock, would assume the form of an irregular 

 inverted cone, the apex of which would be the bottom of the suction pipe 

 of the pump, and the base would be the stationary water level towards 

 the surface of the rock. If the area which forms the base of the water 

 cone is pervious all over to rain water, and remains uncovered, the rain- 

 fall would be partly absorbed by the rock, and so keep an equilibrium 



