280 Recent Progress in Sanitary Science. 



difficult, and which they are altogether incapable of doing. 

 Is not an experience somewhat like the following, familiar to 

 every chemist present? A village has grown into a town, 

 and that town into a city. Its growth has produced manu- 

 facturing communities in the vicinity, which pour their refuse 

 and their sewage into the water-course originally tilled with 

 unpolluted water. The water grows worse to the taste, and 

 stronger to the smell ; and finally popular complaint compels 

 the Board of Water Commissioners to take action. Their 

 first step is to employ a chemist to find out how polluted the 

 water is ; and he finally sends in a report, w r ith a long array of 

 figures in decimals, telling how much silica, lime, magnesia, 

 oxide of iron, phosphoric acid, sulphuric acid, potash, soda, 

 ammonia, nitrous and nitric acids, chlorine and albuminoid 

 ammonia, the water contains. All these data are of interest, 

 requiring much skill in their accurate determination. They 

 tell that a stream may be no worse drinking water than the 

 Thames, the Schuylkill, the Ohio, the Passaic, or some other 

 river, whose water is used at ordinary times by large com- 

 munities without outbreaks of disease directly traceable to 

 it. As in the ease of the Schuylkill, a well-known expert to 

 whom I appealed, said, "Yes, it always analyzed very well, 

 but smelt and tasted very bad." Yet this gentleman drank 

 daily of the Schuylkill water, and so do hundreds of thous- 

 ands, without falling ill of violent maladies. Such analyses 

 do not show how dangerous such drinking-water may be. 

 That danger is known from other facts, independent of the 

 water-analyses. The researches of Klein, Burdon Sander- 

 son, Chevreau, and others, have shown that the germs of 

 infectious diseases may be transported twenty or thirty miles 

 in running water, may pass through thick beds of gravel, 

 sand, etc., without being filtered out, and in fact, can be 

 effectually destroyed only by the operation of an elevated 

 temperature. 



With regard to the chemical methods employed in the de- 

 terminations of the organic constituents of drinking waters, 



