Page:Popular Science Monthly Volume 58.djvu/185

Rh in the basement contains all the necessary apparatus for testing cement, analyzing sand, etc. The laboratory force consists of one biologist and director, one chemist, one assistant chemist and three assistants.

The routine work of the laboratory consists of the regular examination of samples of water from all parts of the watershed and distribution system, i. e., from the driven wells, streams, ponds, aqueducts, reservoirs and service taps. The complicated and varied character of the water supply requires the examination of an unusually large number of samples, and it is safe to say that no water supply in this country is examined more thoroughly and minutely than that of Brooklyn. During the three years that the laboratory has been in operation over eight thousand samples have been analyzed.

The problems of the Brooklyn supply are very different from those met with in Boston. The supply is drawn, not from a few storage reservoirs of large size, but from a large number of small supply ponds, supplemented by an almost equal amount of water from deep and shallow driven wells. There are no extensive swamp areas, but the watershed is sandy and serves as a natural filtering medium. The entire supply, therefore, partakes largely of the character of ground water. The storage of ground water in an open reservoir has been almost always attended with troubles due to growths of microscopic organisms, and the Brooklyn supply has proved no exception to the rule. The mingling of surface water, seeded with plant life, and ground water, laden with plant food, has resulted in the enormous development of microscopic organisms in the distribution reservoirs. During the summer and autumn of 1896 the condition of the water in the city caused general complaint because of its bad odor. An examination, made by Dr. Albert R. Leeds, showed that the diatom asterionella was responsible for the trouble, and that the fishy odor was caused by an oil-like substance secreted by this microscopic plant. Since 1896 growths of asterionella and other odor-producing organisms have recurred regularly in the distribution reservoirs, but by the use of the new by-pass, through which water may be pumped around the reservoirs direct from the aqueduct to the distribution pipes, the water in the city has been kept comparatively free from them. The organisms appear and disappear according to laws that are now beginning to be understood, and while their growth in the Brooklyn reservoirs cannot be wholly prevented under present conditions, the laboratory is doing an important service by constantly noting their condition of growth and by forecasting their effect on the city supply for the guidance of the engineer in his manipulation of the reservoirs. The chief service of the laboratory, however, is in connection with the sanitary condition of the watershed, and upon this most of the bacteriological and chemical work is concentrated. The laboratory was-installed and equipped under the direction of Mr. I. M.