Report on the purification of the Hoogley water for the supply of Calcutta / by Thomas Spencer.

  • Spencer, Thomas.
Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: Report on the purification of the Hoogley water for the supply of Calcutta / by Thomas Spencer. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    TO THE CHAIRMAN OF THE MUNICIPAL JUSTICES OF CALCUTTA. Edston Sqttaee, London, March 12th, 1866. Sir, In furnishing your Engineers with the drawings for my purifying system of filtration, to be adopted at your Water Works, I have been instructed to accompany them with some explanatory remarks ; and also, to refer to the mode and practice of purification, including the material with which it is effected. MECHANICAL EILTRATION. Until recently, no practical system of filtration at- tempted more than to clear out, or strain such mechanical impurities from water as are visible to the naked eye, and which is effected on a large scale in public works, by passing the water slowly through thick layers of sand and gravel. Though in the same system, the whole of the actual work of filtration is apparently performed at the surface of the upper or intercepting layer of fine sand, yet the graduated masses of coarser material, have always been found indispensable to operate below, as retarding or frictional media, to prevent the water from passing through the surface of the fine sand too quickly. Without the intervention of these retarding layers, to operate thus indirectly, the lighter particles of matter are invariably carried beneath the surface, by which the filtering operation is rendered valueless. With a view to diminish the thickness of this lower mass of retarding media—which, apart from its cost, in-