July 10, 1885.] 



SCIENCE. 



31 



I. All soils finer than very coarse sand have 

 practically a continuous capacity for arresting 

 the spores of bacteria from infected air filter- 

 ing through them. 



II. No soil, no matter how fine, can arrest 

 and hold back the spores of bacteria contained 

 in loater. The experiment on which this 

 statement rests consisted in filtering unsteril- 

 ized water through one hundred feet of pipe 

 filled with fine sand which had been sterilized 

 by heating to a red heat. This pipe was con- 

 nected by an air-tight joint with a flask of 

 sterilized beef-infusion, and the whole appa- 

 ratus left for several weeks before use. The 

 first drop of water that passed through these 

 hundred feet of sand infected the beef-infu- 

 sion, causing it to putrefy. 



III. Neither bacteria nor their spores can 

 detach themselves from a liquid or from a wet 

 soil, and pass into the air, except through the 

 conversion of the water into spray, or through 

 the formation of dust by evaporation. 



The chief practical inferences from these 

 results are, that distances, even of hundreds 

 of feet, between wells and cesspools, are no 

 protection against infection, and that a dry or 

 an alternatel}' wet and dry cellar may be more 

 dangerous than a permanently wet one. 



These results emphasize the importance of 

 an intelligent survey of the condition of the 

 soil in selecting a home, and of a legislation 

 prohibiting the pollution of the soil. 



In many towns and cities, the privy-vaults 

 and leaching cesspools of ever^^ house drain 

 reall}' into the sheet of ground-water : the soil 

 arrests the coarse material, the grease and 

 slime ; but the swarming bacteria diflfuse with 

 ease, as much as the soluble chlorides and 

 nitrates, and follow the flow wholly unob- 

 structed. Into this same soil are sunk or 

 driven the wells ; and the water that is drawn 

 for use is polluted in proportion to the num- 

 ber and proximit}' of the vaults and cesspools, 

 on the one hand, and the thinness and slug- 

 gishness of the water-sheet, on the other. In 

 the worst wells in daily use, the water is dis- 

 tinctly colored with sewage ; but the most 

 deadly water may carry only the germs of 

 typhoid-fever or of dysentery, and be other- 

 wise sparklingly clear, and so pure as to pass 

 unchallenged through the most searching 

 chemical analysis. 



If the soil is polluted and very coarse 

 gravel, this indraught, loaded with the spores 

 of bacteria, will flow through the cellar to the 

 warmer rooms. If the soil is polluted and fine, 

 and the ground water-surface rises at any sea- 

 son to the level of the floor, or higher, it will 



evaporate as it oozes into the cellar, and leave 

 an infected dust to be taken up into the cir- 

 culation of the house-air. Similar results will 

 follow from the leaching of the cesspool toward 

 the cellar- wall, or from the filtration through 

 the soil of sewage from a broken or leaky 

 drain ; which is very apt to exist in or just 

 outside of the foundation- wall. The pollutions 

 of soil and water already mentioned are of such 

 a general character, that, with ordinary fore- 

 thought, they can be guarded against ; but 

 there are others of a local character which are 

 not revealed to a general survey. In the 

 growth of many of our cities, the natural topog- 

 raphy is disregarded. Lowlands and marshes 

 which are traversed by sewage-fed brooks are 

 covered with a network of high-graded streets, 

 which convert the blocks into sewage-basins, 

 which come, in time, to underlie blocks of dwell- 

 ings of all classes. 



In other cases, low or marshy ground is 

 made the dumping-ground of the city, and re- 

 ceives the sweepings of the street, the contents 

 of the ash and garbage barrels, — every thing, in 

 fact, that cannot pass through the sewers or 

 be sold. The entire material is loaded with 

 organic matter which is kept in a state of very 

 slow decomposition by moisture. 



Some of the costliest dwellings of our cities 

 rise upon such soil. We may take every pre- 

 caution to avoid in our homes the dangers that 

 arise from a polluted soil, and may j'et fall 

 victims to the filthy condition of remote places, 

 over which we have no control. 



Among many others there are two exception- 

 ally frequent sources of danger of this kind. 

 One of these is the farmer's well, which is rarely 

 safe, and, when not used to adulterate milk, is 

 used to rinse milk pans and cans, and leaves 

 upon their surfaces a source of contamination. 

 The other frequent instance is the use, b}" drug- 

 gists, of water from wells or from cisterns, 

 which are often any thing but sewage-proof. 

 Throughout the country, and often in the cities, 

 the use of only distilled water in compounding 

 medicines is far from universal ; and I have 

 had analyses made of lime-water bought at a 

 druggist's, which was highly contaminated with 

 organic matter. The druggist's well, moreover, 

 is the source of most of the soda-water through- 

 out the country, as well as in man}^ cities where 

 the water-rates are high. A person having a 

 harmless disturbance of the bowels, arising 

 from a cold, is just in the condition to suc- 

 cumb to the dysentery or typhoid-fever lurking 

 in the medicine or Vichj^-water from the too- 

 much-trusted druggist. 



Raphael Pumpelly. 



