Page:Popular Science Monthly Volume 11.djvu/487

Rh producing a magnificent fountain, which is visible from all elevated points throughout the city. By this means the whole body of water is thoroughly aërated before it enters the distributing mains."

The investigation, which consisted of chemical analysis and microscopical examination, began December 14th. Samples of water were taken from Hemlock Lake, from the chief storage-reservoir, and from the city mains. The analysis, which was conducted with great care, indicated remarkable purity of the water. It should, however, be noted that earlier experiments might have shown a different result. The microscopical investigation was also conducted with scrupulous care, and with such precautions as to preclude the possibility of the escape of any important organism. The total quantity of foreign matter obtained was in each case surprisingly small—"a thousand gallons of water yielding not more than one or two grains of residue, a large proportion of which consisted of minute particles of clay and sand." The facts obtained regarding the fish-like odor were of curious interest. The samples of water taken from the lake and from the reservoirs were found to be entirely free from unpleasant odor, while the fish-like peculiarity was plainly perceptible in the water drawn from the main just before it entered the Mount Hope Reservoir. The odor increased in intensity the farther the water flowed through these mains; so that, in the northern portions of the city, it was very offensive. It is noteworthy that all the water which reached the city had passed through not less than four wire screens with meshes a quarter of an inch in diameter, and in no case had a service-pipe been known to be obstructed by any portion of the body of a fish. "In filtering many thousands of gallons of water, at different times, and under such conditions as to arrest multitudes of the minutest organisms, not the smallest fragment of a bone, or fin, or scale, of a fish—parts which would longest resist decomposition, and float away in the water—has ever been detected."

In answer to the question, "What cause, then, can be assigned for this most peculiar odor?" Prof. Lattimore asserts that it must be due to the decomposition of some form of fresh-water algæ. He draws his conclusions partly from the investigations of others, and partly from his own observation and experiment. After the disappearance of the odor from the water, he observed that microscopic algae, which had collected on the filters through which water had been flowing for twenty-four hours, exhaled an odor strikingly like that given off by a blade of early spring grass, when crushed by the fingers. A minute quantity of these algæ put into distilled water, and kept covered for a few hours, revealed an odor which was distinctly recognized as that which had recently affected the water from the lake.

This experiment, with others pointing in the same direction, leads to the conclusion that the fish-like odor must be due to some obscure condition of the algæ—most likely to their decay and decomposition.