420 REPORTS ON THE STATE OF SCIENCE, ETC. 
In May 1926 the trial hole was tested. This hole was 8 in. in diameter 
and 300 ft. deep, and was found to justify the development of the site. 
By January 1927 the first of two permanent boreholes, 32 ft. apart, each 
23 ins. diameter and 300 ft. deep had been sunk and tested. The second 
permanent boring was sunk and tested by the following July. The trial 
boring was 5 ft. distant from No. 1 borehole and 31 ft. from No. 2 borehole. 
The table below summarises these tests. 
The great variation in tests may be traced mainly to the effect of opening 
out the strata by several borings and also the result of clearing by extended 
pumping. It is obvious that in such strata any conclusions as to the true 
yield can only be arrived at after many tests or prolonged pumping. 
SuMMaARY OF TESTS ON BOREHOLES. 
DuRATION ONE TO FIvE Days. 
* Specse 
uantity | Rest . yield. 
Test. Date. Hole. | Gals. per | Level ion RewOr, Gals. per 
hour. Feet. * | hour per 
foot. 
I May 1926 . | trial 4,840 25 43 I10 
3 January 1927 .|No.1 10,500 26 70 150 
6 | February 1927 . |No.1]| 10,000 28 44 227 
8 | July 1927. . |No.2] 15,500 25 113 138 
9 | January 1929 «6. | No.2] 12,500 29 59 212 
1o | January 1929 «6. |No.1| 12,500 | 29 44 284 
2. A summary of the facts concerning wells in the Chalk which have 
been gauged for continuous long periods—varying from a minimum of 
three to a maximum of eighty-four years—will be found in Table I of ‘ The 
Hydro-Geology of the Chalk of England,’ Trans. Inst. Water Engineers, 
vol. xxxiv, 1929. 
APPENDIX E (d). 
NOTES ON RAINFALL, REST-LEVELS AND PUMPING LEVELS 
IN THE CHALK 
as deduced from records supplied by 
A. E. CoRNEWALL-WALKER. 
The East Surrey Water Company. 
The records consist of graphs, for 1924 to 1930 (inclusive), at the Purley 
Well, of (a) Rest Level ; (6) Pumping Level, and (c) Rainfall. 
From a study of the graphs the following points emerge :— 
(1) The low degree of porosity is shown by the way in which the rise off 
the water level lags some four months behind periods of heavy rainfall. 
(2) Irregularities in the rainfall curve tend to become smoothed out in 
the rest-level curve ; thus, at one point, two ‘ peaks ’ in the former produce 
one in the latter. 
(3) After long periods of heavy rainfall the water-level remains high for a 
