Lecture by W. Arnold Evans, Esq., M.D., medical officer of health for Bradford, on water supply : delivered in the Court House, Wakefield, on Saturday, April 30th, 1892, being the eighth of a series of twelve lectures on sanitary subjects ... [etc.].

  • Evans, W. Arnold.
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Lecture by W. Arnold Evans, Esq., M.D., medical officer of health for Bradford, on water supply : delivered in the Court House, Wakefield, on Saturday, April 30th, 1892, being the eighth of a series of twelve lectures on sanitary subjects ... [etc.]. 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.

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    li date, locality, name of collector, and any other necessary note being inscribed in legible writing. In the actual analysis, which should be made as soon as possible after collection, the first points to be noted are the appearance, colour, reaction, smell (if it has any) and taste of the water. If there be any turbidity or sediment, some of the water may be set aside in a conical glass, and the deposit, after settling, examined microscopically. All products of animal life may be met with in the deposit, viz., epithelial scales, bits of muscular fibre, &c. These unpleasant objects when occurring in drinking water afford strong evidence that such water is seriously polluted with animal products, and unfit for any domestic supply. Vegetable matters, such as pieces of cotton, linen, hemp, or woody fibre, indicate that refuse from human habitations finds its way into the water. The deposit in water taken from stagnant pools or the bed of rivers frequently contains many beautiful forms of diatomacese, and if your lens be strong enough different varieties of bacteria, including micrococci and bacilli, may be seen. Clusters of micro- cocci may be found in comparatively pure water, and I do not know that their presence is particularly significant; but large bacilli and wriggling spirilli have a certain import, for they can only live in water which contains organic matter in solution. The next point in our analysis is to ascertain the total amount of solid matter contained in the water, expressed in terms of grains per gallon. The following table, taken from Mr.Wanklyn's Water Analyses, shows the quantity of solids contained in some of the largest water supplies in the country :— Grains per Gallon. London, Thames Companies 18.5 ,, New River 17.6 ,, Kent Company 26.5 Manchester Water Supply 4.7 Glasgow, Lock Katrine 2.3 Bala Lake 3.2 Srarbiough Reservoir 28 7 Atlantic ocean 2688.0 Distilled Water 0.1 All these, with the exception of the last two, are wholesome waters, although the amount of total solids shows considerable variation. Provided the total solids do not exceed forty or fifty grains per gallon, the quantity of solid matter in itself is no objection to the adoption of the water as a domestic supply. A further point in the analysis of water is the determination of the amount of chlorine, not of course free chlorine, but chlorine in combination with some metal such as sodium, with which it is usually found combined in the form of sodium, chloride, or common salt. Although an excess of chlorine is in itself no serious fault in a water, provided it is not so excessive as to render it unpalatable, yet the presence of a large amount points to contamination with sewage ; the reason of this being that urine and sewage contain large quantities of sodium chloride, and the great majority of natural waters in an unpolluted state contain comparatively small amounts. If, therefore, the water analysed is found to be free, or almost free, from chlorine, it is unpolluted with sewage ; but if chlorides are present in quantity, animal matter has probably found its way into the water, and a more complete analysis is required. The absence or presence of chlorine, however, gives no information as to whether or not there is contamination by vegetable organic matter. The following list taken from Mr. Wanklyn's book shows the quantity of chlorine in some waters analysed by him :—