Army manual of hygiene and sanitation, 1934 / [War Office].

Date:
1941
Catalogue details

Licence: Public Domain Mark

Credit: Army manual of hygiene and sanitation, 1934 / [War Office]. Source: Wellcome Collection.

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    t outcrops may be found where strata come to the surface of the earth, as on the sides of hills. 7 ; Water that has soaked through the soil percolates down- wards until it reaches the first impermeable stratum and runs along. its upper surface in an underground stream until it reaches an outcrop where it flows out on the surface as a surface or land spring. It may be held up in a depression to form an underground lake or it may get through a fissure or crack and percolate downwards until it reaches another impermeable stratum. C Springs. D Deep wells. E Shallow wells. Fic. 6.—Underground Water. Showing springs, deep wells and shallow wells in relation to the permeable and impermeable strata of the earth. Underground water lying above the first impermeable stratum is called “‘ subsoil ’’ water. . Underground water may be tapped by means of wells sunk into the earth. Shallow wells tap the subsoil water, while deep wells are those which are sunk below an im- permeable stratum and tap the water lying on a deeper impermeable stratum. The classification of a well as shallow or deep depends on whether it taps the subsoil water or water below an impermeable stratum; a deep well may be com- paratively short in length where the impermeable stratum is near the surface of the earth.