. Preventive medicine and hygiene. us rock,for limestone is not porous. The water travels through fissures or pas-sages. T^Hien these are large they are called caverns or cavea, as, forexample, the Mammoth Cave in Kentucky. These caverns or caves arenatural seams or cracks enlarged by the gradual solution and removalof the limestone by the passing water. Limestone is the only commonrock that is soluble in this way, and, for water supply purposes, lime-stone formations must be distinguished from all others. The crevices may be, and often are, continuous for many are remarkably tortuo
. Preventive medicine and hygiene. us rock,for limestone is not porous. The water travels through fissures or pas-sages. T^Hien these are large they are called caverns or cavea, as, forexample, the Mammoth Cave in Kentucky. These caverns or caves arenatural seams or cracks enlarged by the gradual solution and removalof the limestone by the passing water. Limestone is the only commonrock that is soluble in this way, and, for water supply purposes, lime-stone formations must be distinguished from all others. The crevices may be, and often are, continuous for many are remarkably tortuous and anastomose freely, and the directionand flow of the water bear no relation whatever to the surface topog-raphy. Pollution at one point may, therefore, endanger those usingthe water at a far distant place. Limestone formation has little ability to hold the abundant winterflows to maintain a supply through droughts. The difference betweenlimestone and sand in this respect is striking, and, from a sanitary SOURCES OF WATER 811. standpoint, the fact tliat water flowing through sand is filtered andpurified, whereas no sneh action takes phice through limestone fissures,is significant. AVhile much water is frequently availahle at one pointin limestone formations, the amount is suhject to greater fluctuations,and the supply may fall short when most needed. That contamination at one point may soon reappear at a far distantpoint may be demonstrated by the use of fluorescent dyes, or by the useof massive cultures ofsome harmless micro-organism, such asyeast or Bacillus fro-digiosus. In our countrySan Antonio, Texas,is supplied with w^aterfrom limestone springsflowing in greater vol-ume. Indianapoliswas at one time andWinnipeg in Canadais still supplied large-ly from this in France ispartially supplied withlimestone Avater. A^i-enna obtains its sup-ply from the wonder-ful Kaiserbrunnenand other limestonesources, which are allin the high mountains,where there is scarcely
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Keywords: ., bookauthorwh, bookcentury1900, bookdecade1910, booksubjecthygiene
