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.
58/414 page 48
![KENT WATER SUPPLY. They occur also where the Thanet Beds are present (between the Beading Beds and the Chalk), especially where these are comparatively impervious, as in East Kent. In what is probably the earliest systematic description of swallow-holes (and in Kent) Sir j. Prestwicii has well summarised the essentials for their formation, on hill-slopes: those in the bottoms of stream-valleys are another matter. His words are as follows: “ It would appear that two condi- tions are essential for the formation of swallow-holes: the one, that there should be streams formed at such a level that they have to pass over a surface of country higher than that of the main valleys of drainage; and the other, that the line [plane] of water level in the mass of calcareous strata in which the swallow-holes are formed should be below the level at which the streams drilling the swallow-holes are absorbed.” Mr. Gr. Dowker has noted that at Woodnesborough “ there are large ‘ swallow-holes ’ which absorb the water from the surface and convey it some distance underground.” f1) It is from the above-quoted paper by Sir J. Prestwich(2) that the following details of swallow-holes are taken: they were not given in the B.eport above mentioned. It deals with the neighbourhood of Ensinge, a few miles westward of Canterbury, and the tract referred to is at the southern end of the Tertiary hills in part marked as Fishpond Wood on the old Ordnance Map (Sheet 3) and “ extending over the London clay and Lower Tertiary sands down to the edge of the chalk. The drainage from this clay surface is carried off by several small brooks (not marked on that map) having an easternly or a southerly direction . . Skirting the wood from Nick-hill (Nackholt) Farm westward to Lower Elmsden (Ensinge) there are to be found within a distance of about a mile as many as six or seven of these water-courses, all of which . . disappear just within the edge of the wood, in swallow holes, some of which are not more than 6 or 8 feet broad and deep, whilst others attain a diameter of 30 to 40 feet and a depth of 20 to 30. There is generally not much water in the brooks running into these funnel-shaped excavations, at the bottom of which they form a small pool, that, not- withstanding this incessant addition, remains unchanged and without rise, the water being gradually and quietly absorbed as fast as it is supplied. Only occasionally after heavy rains the water stands for a few hours some feet higher. The sides of the excavations are usually sloped with debris, grass, and bramble, and the bottom covered by a bed of sand and gravel so that the chalk surface cannot often be seen. Some of the swallow holes are situated within the boundary of the Lower Tertiary sands, whilst others are just on the edge of the chalk. Between this spot and the river Stour at Shalmford Street there is a descent probably of 200 to 300 feet [less than 200], throughout which the surface of the chalk is as bare of wood 1 Oeol. Mag., dec. iii., vol. iv., 1887, p. 204. 2 Quart. Journ. Qool. 8oc.t 1854, vol. x., pp. 222-224.](https://iiif.wellcomecollection.org/image/b28126737_0058.jp2/full/800%2C/0/default.jpg)
