Excerpt from The Self-Purification of Streams Such observations are, however, open to misinterpretation. The mixing of the befouled water With the purer water of the river becomes more complete the greater the distance from the source of pollution, and When the increase in the volume of the stream from tributaries, and especially from underground sources, is also taken into consideration, a sufficient explanation is afforded for the changes observed. The thorough mingling of the polluting matters With the total volume of water in the stream, combined with a continuous and often rapid increase in the volume of the stream itself, may dilute sewage to such a degree that it seems as if the polluting sub stances had been materially lessened or had altogether disappeared. It is quite evi dent, however, that, While such dilution may improve the general appearance of a river water, it does not by any means follow that noxious elements introduced With the pollu tion are destroyed. Typhoid bacilli, for example, that enter a sewage-polluted river may persist in the river water, so far as the unaided senses can determine, for many miles below the point of entrance, although the water of the stream may to all outward appearances have quickly regained its pristine purity. Dilution in itself can neither remove nor destroy dangerous substances; it may, in fact, mask their presence. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.