Hygiene and public health / by B. Arthur Whitelegge.

  • Arthur Whitelegge
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Hygiene and public health / by B. Arthur Whitelegge. Source: Wellcome Collection.

    74/610 (page 62)
    vary according to season, the well must be deep enough to reach its level in times of drought. Such a well drains a wide area, and is liable to be polluted by any impurity of the soil within a considerable radius of its mouth, and as the supply is at best subsoil water, due regard must be had to the possibility of pollution at comparatively distant points. It should be lined with brick and puddled, and the brick lining should be brought a foot or two above the ground so as to exclude surface washings. If the soil is polluted, or if the Fig. 5.—Diagrammatic Section across a Valley. a a. Level of water iu deeper periueahle strata. water found is impure or insufficient in quantity, the boring is carried through the first impervious stratum to other water-bearing strata deeper down. Some- times the water in the deeper strata is under sufficient pressure to make it rise to the surface and overflow, forming an artesian well or artificial spring. The flow in dense strata being slow, each well exhausts a considerable area, and the yield of water cannot be greatly increased by multiple borings. Borings in sandstone or limestone give large and constant supplies, owing to the enormous accumulations of water they contain, but wells in superficial sand or gravel beds, or chalk, often fail in dry seasons (Fig. 5). Tube wells are convenient for small or temporary supplies. A jointed iron tube is driven into the