146 
THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
favourable to some such scheme, and some of the observations 
elicited are recorded below :— 
Mr. Conder, C.E., stated that the idea was good and 
feasible, and that the natural storage places for flood waters 
were the pervious water-bearing beds. 
Mr. Baldwin Latham, C.E. , pointed out that in India 
water was long ago stored in this manner. 
General Hyde, of the Indian Railways Department* stated 
that in Pesliawur, the natives have cut channels, in the rainy 
season, from time immemorial, so as to fill up a gravelly 
stratum, into which they make their wells through an over- 
lying impervious deposit. 
Sir Frederick Abel, C.B., F.R.S., the Chairman of the 
Conference, commented on the subject, and spoke of its great 
importance. 
Mr. C. E. De Ranee, A.I.C.E., F.G.S., has expressed the 
opinion* that the particular scheme set forth in these pages 
would succeed. 
Until quite recently (January, 1888), I was not aware 
that anyone had proposed utilizing the river gravels for the 
storage of water, but I notice— 
Professor Prestwick, F.R.S., has suggested! the use of the 
Thames gravel as a storage reservoir for flood water, whereby 
the winter water might- be conserved, and used to increase 
the summer flow of the river, by damming back at a narrow 
part, and conducting it to a lower level down the river in 
time of drought. 
Swallow Holes. 
To show that the estimations previously given as to the 
capacity of artificial swallow holes are not exaggerated, I 
propose to give now a few instances of the results obtained by 
some natural and artificial ones. 
In Hertfordshire, a number of natural swallow holes bring 
the rainfall of an isolated clay basin of twenty-three square 
miles, lying outside the basin of the Lea, to feed the Amwell 
springs within the Lea basin, long since used by Sir Hugh 
Middleton to fill the New River. 
Clay resting on chalk is sometimes drained by sinking 
dumb-wells and filling them with flints. 
* Northampton Papers, October, 1884. 
f “ Kainfall and Evaporation,” by Symons, Greaves, and Evans. 
Excerpt Minutes of Proceedings of the Institution of Civil Engineers, 
1876. 
