Manual of practical hygiene / ed., F. S. B. François De Chaumont, M. D., F. R. S.

  • Edmund Alexander Parkes
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: Manual of practical hygiene / ed., F. S. B. François De Chaumont, M. D., F. R. S. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    35/806 (page 11)
    A double filter can be made by having a second chamber. Whatever be the size of the reservoir, it should be kept carefully clean, and no possible source of contamination should be permitted. In the large reservoirs for town supply, the water is sometimes rendered impure by floods washing surface refuse into them, or by substances being thrown in. In fact, in some cases, water pure at its source becomes impure in the reservoirs. Some large cities are still supplied principally by rain-water, as Con- stantinople,—where under the houses are enormous cisterns,—Venice, and other places. Gibraltar and Malta are in part supplied in this way. As far as possible, all reservoirs, tanks, &c., should be covered in and ventilated; in form they should be deep rather than extended, so as to lessen evaporation, and secure coolness. Though they should be periodically and carefully cleaned, it would appear that it is not always wise to disturb water plants which may be growing in them; some plants, as the Protococcus, the Chara, and others, give out a very large amount of oxygen, and thus oxidise and render innocuous the organic matter which may be dissolved in the water movealle covering j'tone ^Pavivg Level oj Ground. Fig. 1. or volatilised from the surface.^ Pr. Chevers mentions that the water of some tanks which were ordered to be cleared of water plants by Sir Charles i^apier, deteriorated in quality. Other plants, however, as some species of duckweed (Lemna at home, Pistia in the tropics), are said to contain an acrid matter which they give off to the water. It would be well to remove some ot the plant, place it in pure water in a glass vessel, and try by experiment whether the amount of organic matter in the water is increased, or whether any taste is given to the water. The presence of some of the Nosfoc family gives rise to an offensive pig-pen odour when decaying.2 Dead vecretable matter should never find its way into, or at any rate remain in, the reservoir VVhenever a reservoir is so large that it cannot be covered in a second smaller covered tank, capable of holding a few days' supply, miaht be pro yided, and this might be fitted with a filter, through whichthe water of the large reservoir migbt be led as required. When tanks are large they are made of earth, stones, or masonry; if mortar J Clemens in Archiv.fiir Physiol. Heillc, 1853. ohv!eu]T(ilf;f^S!'' ^'^^ ^'P'' ^'^'^ of Health, &c. of Afassa-