TRANSACTIONS 
OF THE 
bull Scientific 
AND 
Ficld Waturalists’ Club. 
EpITED By THOMAS SHEPPARD AND J. R. BOYLE, F.S.A. 
OUR WATER SUPPLY. 
By Rev. H. P. SLADE, M.B.A.A. 
Y lecture on this subject, which was given to the Club 
on the gth of November, 1898, was principally of 
a popular and general character, and it was only at the end that 
it assumed a topical aspect. The subject was dealt with generally 
under the following four heads :—Evaporation, Condensation, 
Precipitation, and Percolation, and was worked out as fully 
as time permitted. 
Since its delivery a pamphlet has been placed in my hands 
by Mr. Thomas Sheppard, written by Mr. John Robert Mortimer 
in 1879, entitled “The Chalk Water Supply of Yorkshire.”* 
This appears to me to be more worthy of reproduction here 
than my lecture, since the information contained therein is 
entirely of local interest. After recording those portions of my 
lecture which are of local or exceptional value, Mr. Mortimer’s 
paper is being reprinted ; and I have put as footnotes thereto, 
such remarks as I have to make. 
In answer to the question, How long will our present supply 
of water last? I gave what I conceived to be a very moderate 
estimate, mainly based on the chalk outcrop in East York- 
shire, which I concluded embraced an area of about 240 square 
miles. This is less than Mr. Mortimer gives, while his figures 
are slightly in excess of those deduced from a geological map, 
given by Mr. John Phillips, F.G.s., in his work, “ Illustrations 
* Proc. Inst. Civil Engineers, vol. lv., pp. 1-9, with map and sections, 
