The water supply of Kent : with records of sinkings and borings / by William Whitaker ... with contributions by H. Franklin Parsons ... Hugh Robert Mill ... and J.C. Thresh ... Pub. by order of the lords commissioners of His Majesty's Treasury.
- Whitaker, William, 1836-1925.
- Date:
- 1908
Licence: In copyright
Credit: The water supply of Kent : with records of sinkings and borings / by William Whitaker ... with contributions by H. Franklin Parsons ... Hugh Robert Mill ... and J.C. Thresh ... Pub. by order of the lords commissioners of His Majesty's Treasury. Source: Wellcome Collection.
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![SWALLOW-HOLES. Whilst for the most part water gets into the Chalk by percolation through the soil, there is another method by which local additions of water are more rapidly made, and this is sometimes of importance in regard to the possibility of pollu- tion occurring, as it obviously may, if water that has bowed over the surface of the ground and perhaps acquired undesir- able matter in so doing, gets into the Chalk in a somewhat direct way. This sinking of water into the Chalk has been described in various Geological Survey Memoirs., and the notes on the subject, as far as the Thames Basin is concerned, were collected together as a Memorandum for the Royal Commis- sion on Metropolitan Water Supply (1893, Appendices, pp. 430-433). It will be useful to reproduce this as far as regards Kent, with some slight alteration in form, and then to add notes on other swallow-holes. Swallow-holes, that is, more or less funnel-shaped hollows which swallow up streams that run in to them, are common. They are formed by streams which, rising in the higher ground, flow down the escarpment of the Tertiary beds, until they reach the more pervious and jointed Chalk, into which they sink, or until they come within a short distance of that rock, when they work their way into it through the few feet of the softer overlying beds. In the course of time, through the chemical action of the carbonic acid in the water, and the mechanical action of the water itself, funnel-shaped basins are worn in the Chalk and the beds above, the operation being made more easy by any pre-existing fissures. These hollows are often thickly overgrown with vegetation. The streams may sometimes be seen running down them, though some- times they merely flow into a small pool, the level of the water in which remains the same, notwithstanding the constant inflow. Mu. F. J. Bennett has come to the conclusion that “ all swallow-holes, in their first stages, began from below.” He adds: “ swallow-holes [presumably those in valleys] seem to me to have passed through a series of stages; being initiated by an upward pressure of water, and that where they now absorb water they are in a later stage.”(x) For present pur- poses, however, we have only to do with the downward stage. On the northern side of the London Basin these swallow- holes mostly occur at or near the junction of the Reading Beds and the Chalk. They sometimes occur, however, at a distance from the Tertiary beds, and sometimes well within their boundary (where the lower beds are sandy). 1 “ Ightham : The Story of a Kentish Village,” 1907, pp. 129-131 j see also p. 128.](https://iiif.wellcomecollection.org/image/b28126737_0057.jp2/full/800%2C/0/default.jpg)
