A manual of hygiene and sanitation . ate of percolation has much to do with the com-pleteness and perfection of this action, for ample timemust be had for the organic decompositions to , anything that retards the downward flow ofwater favors its purification, and anything that increasesits movement decidedly affects for the worse its ultimatequality and character. The importance of this biologic soil action can scarcely 156 WATER. be overestimated, and the student should endeavor toappreciate not only the bearing which it has in the greatscheme of natures adaptation of means to
A manual of hygiene and sanitation . ate of percolation has much to do with the com-pleteness and perfection of this action, for ample timemust be had for the organic decompositions to , anything that retards the downward flow ofwater favors its purification, and anything that increasesits movement decidedly affects for the worse its ultimatequality and character. The importance of this biologic soil action can scarcely 156 WATER. be overestimated, and the student should endeavor toappreciate not only the bearing which it has in the greatscheme of natures adaptation of means to ends, but alsothe importance of our utilization of it in the artificial puri-fication of our environment and in the disposal of wastematters. We must understand, however, that for everysoil only a definite amount of work can be accomplishedby the agencies mentioned and under the conditions exist-ing at any given time. In other words, there is here alsoa limit of permissible impurityy and if this limit is exceeded, Fig. 26. pervi ous. Outcropping of water-table. (Harrington.) the conditions become unnatural, the bacterial and chemicaction is inadequate, and the descending water is notthoroughly purified as it percolates through the over-charged soil. The subsoil-water slowly sinks through the ground untilat some level or other it reaches an impermeable stratum,where it is retained in natural basins or escapes at someoutcropping of the stratum below the water-level, thusforming a spring. (Fig. 26.) The level of the waterin these underground reservoirs is constantly changing WELL-WATER. 157 according to the season, rainfall, discharge from springs,etc., though ordinarily the variation for any given placediffers little from year to year. It is from wells sunk tothese water-bearing strata and from springs that wateris obtained for the majority of people Avho do not live intowns or cities supplied by water-works. These under-ground bodies of water are in constant motion toward oneor
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecthygiene, bookyear1903
