Public health : complete volume.

Date:
[between 1900 and 1920]
Catalogue details

Licence: In copyright

Credit: Public health : complete volume. Source: Wellcome Collection.

    16/246 page 12
    What are the Contents of Bain Water near Towns ? Soot, vegetable debris, carbon dioxide, lead, ammonia, and sulphuric acid. Is Rain Water used for iJrinJdng Purposes ? Very seldom. Gibraltar depends upon rain water. It is only when all other resources are either scarce or dangerous that rain water is relied upon. What is Ground Water ? Rain soaks into the soil and descends until it meets an impervious straGini. The sheet of water which collects at this region is known as “ ground water,” and is constantly moving because it follows the inclination of the land. What is the Nature of this Ground Water ? It is charged with carbon dioxide, oxygen and nitrogen. Also calcareous salts may yield COg as the water comes in contact with them. Ground air also gives up CO2 to the water. Ground water near graveyards, cesspools, etc., may feed shallow wells with a rich sparkling water which is in reality highly dangerous. What is a Spring ? It is an outc.rop of water which may have emerged from the edge of an impervious stratum. The water is held down by an impervious layer, it may be of clay, but as soon as there is a break in the continuity of this layer the retained water forces its way to the surface there to appear as a spring. What is a Well ? It is really an artificial spring formed by making au excava¬ tion in the ground. Wells are of two varieties, shallow and deep.
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