94 



MB. W. E. BALDWIN-WISEMAX OX 



[Feb. 1907. 



all traces of the salt long after the experiments had terminated: 

 and the whole test was an excellent object-lesson of what may be 

 expected when a water-bearing rock is overpumped in the vicinity of 

 the sea — an experience which has been realized in more than one 

 seaside resort deriving its water-supply from sub-surface sources. 

 Also, for the reason that the temperature of a solution and the 

 nature of the salt affect so radically the rate of flow, it seems to me. 

 although this point has not previously received the attention that 

 it deserves, to be most essential that the temperature and density 

 of any underground stream should be recorded wherever and when- 

 ever possible, as, without these data, experimental records are not 

 directly comparable. 



III. ExPEBZtfEXTAL DATA OX YaELATIOX OF PbESSUBE IN THE 

 IXTEBSTICES OF A ROCK. 



Various investigators have endeavoured to measure the basal area 

 of the cone of depletion produced by any specific pumping in a 

 locality, but not infrequently, owing to an insufficiency of data, the 

 area of depletion has been very arbitrarily delimited. 



Prof. Boyd Dawkins, in his most interesting lecture, ' On the 

 Relation of Geology to Engineering ' (1), to which I have pre- 

 viously referred, gives a fairly lengthy list of measured cones of 

 depletion in the Chalk; one of which, that produced when pumping 

 6-| million gallons a day at the Mill-dam Pumping Station of the 

 Hull Corporation, is particularly interesting owing to the fullness 

 of its detail. 



Eoadley (25) in the Maiden experiments very carefully investi- 

 gated the rate of growth of a shallow cone of depletion, when 

 steadily pumping 2300 gallons an hour for 10 hours from a 3-inch 

 well through a l|-inch pipe. The difference of level in bores 5 feet 

 10 inches apart is shown in the following Table (Till) :- — 



Table VIII. 



No. of hours 



from the 



commencement. 



I>rop of level when pumping 2300 gallons an hour. 



At well. 5ft.lQirt3./roiHZCcll. 



1 1 ft. 8 ins. from well. 



1 



2 



2-23 

 2-38 

 2-48 

 2-53 

 2-58 

 2-61 

 262 

 264 

 2-66 

 267 



0-52 

 067 

 0-75 

 0-81 

 0-84 

 0-86 

 0-89 

 092 

 0-94 

 097 



0-49 

 065 

 073 

 079 

 0-81 

 0-84 

 0-86 



3 



4 



5 



6 



7 



8 



0-89 



9 



o-yi 



10 



0-04 



