This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1880 Excerpt: ...perfectly well recognised by the ancient Romans. Frontinus tells us that it pleased the Emperor (as be puts it) to order that the water supplied by certain aqueducts should be furnished to the people for domestic purposes, while that supplied by some others, from its being occasionally turbid and of inferior quality, ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1880 Excerpt: ...perfectly well recognised by the ancient Romans. Frontinus tells us that it pleased the Emperor (as be puts it) to order that the water supplied by certain aqueducts should be furnished to the people for domestic purposes, while that supplied by some others, from its being occasionally turbid and of inferior quality, was to be used for " viler purposes." As, however, we do not, as a matter of fact in the majority of instances, imitate the ancient Romans, either in this particular or in bringing pure water from a distance to supply the towns, but use the nearest water that we can get, whether good, indifferent, or bad, it is of course necessary for us to do all that we can to purify it before use. This is done on a large scale by filtration through layers of sand and gravel, after the coarser suspended matters have been allowed to deposit themselves in a settling tank. I shall not describe this method of filtration in detail here, as it is a little beside the scope of these lectures, but, as the principle on which it acts is the same as that upon which the success of most forms of domestic filter depend, I may say a few words about it once for all. The experiments made by Dr. Frankland for the Rivers Pollution Commissioners showed that when foul water was passed through layers of porous soil, or sand and gravel, the amount of organic matter in it was reduced, if two conditions were fulfilled; these are, that the filtration be downwards and intermittent. It was found that if the filtration were upwards or continuous, no such purification occurred after a time. The explanation of these facts is simple. The filtering material acts in two ways. It separates, mechanically, suspended matters in the water that are too large to pass through the pores of th...
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