INLAND WATER SURVEY © 415 
some distance down-dip—yet still well inland, as at Lincoln (Boultham). 
In other cases sea-water may gain access to concealed water-bearing rocks 
near the coasts or in estuaries—as in parts of Essex, Kent and Sussex. 
It is required to discover the approximate line at which the water becomes 
unpotable, and the underlying causes of the change. Help from geo- 
physicists may be obtained in future, for already it is thought by some to 
be possible to detect the change from fresh to saline waters in buried rocks 
by means of instruments. Again, changes in the mineral content of water, 
where permanent pumping machinery has been in action for many years, 
are apt to recur pari passu with lessening yield. Quite apart from changes 
that may occur as the distance increases down-dip, or as the overlying 
geological cover may alter in character (e.g. in some Chalk areas), research 
is needed on the relative qualities of waters derived from definite individual 
strata. These ought to be studied much as a palzontologist concentrates 
on fossil zones. The form of mineral analyses of waters seems to require 
standardisation so that rapid comparisons may be made. It frequently 
happens that a bore taps two or three water-bearing horizons, and the 
analysis made is that of a mixed water. One of the sources, from a 
particular bed, may be known from previous research to be highly saline. 
If located and tubed off the quality of the remainder would be improved. 
Other problems for study—Amongst other problems to be studied are 
(a) the prevention of pollution of underground waters by sewage and 
soakaway, (4) the possible repletion of underground reservoirs by means of 
dumb-wells, (c) the effects of mining on the distribution of underground 
waters. 
Conclusion—Records as complete as possible should be secured of all 
new wells or borings, and studied from every point of view. Such work 
can be undertaken only by persons with special qualifications as hydro- 
geologists. 
2. OUTLINE OF THE RECORDING AND ASSEMBLY OF DATA. 
CoNTINUOUS MEASUREMENTS OF WATER LEVELS. 
» Records of water levels during static periods or whilst pumping is in 
progress are kept at the larger water undertakings in the country and 
occasionally also at private wells (see Appendices (a), (b), (c), (d)), some 
covering as much as eighty years; but few of these (apart from those 
within the orbit of any economic unit) have been brought into regular and 
continuous relationship with others outside, although several undertakings 
may draw water from the same geological formation in the same drainage 
area. Hence the regular construction of maps or diagrams showing the 
(say, monthly) variations in the water-table has been impracticable hitherto. 
Useful maps and diagrams and empirical rules as to fluctuations to be 
expected have indeed been issued from time to time in printed papers or 
water supply memoirs (see Appendices (d) and (e) and Bibliography) ; but 
usually the maps refer to only one or perhaps two isolated periods in any 
one year, or to a mean annual level alone. 
An excellent summary of the kind of observations that might be and 
frequently are taken at pumping stations and private wells will be found 
in the Report on Stream Flow and Underground Water Records, Section II, 
C and E, issued by the Committee of the Institution of Water Engineers 
(October 1929), under the chairmanship of Dr. H. Lapworth. 
Flow from springs could be measured by weirs. ; 
» Collection of general water-supply data.—With regard to the collection 
of widespread geological and water-supply data derived from the sinking 
