Wood's Medical and Surgical Monographs . nfluence ofmeteoric showers upon the richness of spring water in bac-teria. In this diagram the shaded spaces bordered by an inter-rupted line represent the average richness in microbes of theVanne during the year 1889; the continuous broad curve, thetemperature of this water drawn from the reserv^oir of Mont-rouge; finalh% the rectangular shaded spaces above indicatethe heights of rainfall during the same weeks in the Parisianregion. 490 Bacteriological Analysis of Waaler. It will readily be seen in this diagram that the increase o£bacteria in Vanne wa
Wood's Medical and Surgical Monographs . nfluence ofmeteoric showers upon the richness of spring water in bac-teria. In this diagram the shaded spaces bordered by an inter-rupted line represent the average richness in microbes of theVanne during the year 1889; the continuous broad curve, thetemperature of this water drawn from the reserv^oir of Mont-rouge; finalh% the rectangular shaded spaces above indicatethe heights of rainfall during the same weeks in the Parisianregion. 490 Bacteriological Analysis of Waaler. It will readily be seen in this diagram that the increase o£bacteria in Vanne water received at Paris corresponds to allconsiderable rainfalls. In summer, this phenomenon is lessapparent, because the showers evaporate rapidly or are easilyabsorbed by the dry earth; but in spring and autumn the soilremains moist and is soaked to excess. These examples of the variability of the micrographic com-position of water show that a single analysis of a given watercannot definitely establish its average richness in microbes:. Fig. 19.*—The Relation of the Purity, in Bacteria, of Spring Waters to the Fall of Rain. indeed, an analysis made in summer will generally give a min-imum number of germs; during the winter and the humidperiods of spring and autumn, on the contrary, one will ob-tain a maximum number. I say humid, and not icy, periods,for it will be observed that during long-continued snows andcold, when the temperature is below 0° C, spring water ac-quires a very great purity. * By mistake, the diagram (Fig. 19) indicates an increase beyond8,000 bacteria durinp: the third week of July, 1889. The number ofgerms observed during this week was found to be exactly 1,025 germsto the cubic centimetre; that is, than the number mentioned forthe two weeks preceding. Bacteriological Analysis of Water. 491 Many other interesting- facts are brought to light by thequantitative analysis of water; we rely upon it in determining-the filtering power of soils; and in thi
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