or WATEK FOK ORGANIC MATTER. 87 



The chloride of sodium in a sewage stream of a very 

 sluggish nature was estimated. The following numbers 

 were obtained in the course of 14 miles : — 



8-97 7-93 



7"53 7*78 



6'25 662 



778 40-89 



The numbers are pretty uniform_, although they rise and 

 fall with evaporation and the additions made to the stream ; 

 but whenever certain manufactures come in^ a sudden rise 

 is observed. Before this occurs_, I believe the chloride of 

 sodium is a perfectly exact comparative measure of the 

 amount of sewage. It may in many cases also be made 

 into a positive measure. This will^ however, depend on 

 the mode of managing the sewers. 



The conclusion simply is, that chloride of sodium is the 

 most abiding constituent of sewer-water, and, with due 

 precaution, the best index of comparative amounts in the 

 original sewage. When decomposition has not taken 

 place, it may also be used for indicating the comparative 

 strength or value of sewage-water. 



Perhaps it will be thought that in here speaking of the 

 impurities of water, when the River Commissioners are 

 making their inquiry in Lancashire, it would be better if I 

 spoke less of the laboratory side of the question, and more of 

 the great evils which have destroyed the beauty and use of 

 our rivers. On one important point I am of the same 

 opinion which years ago I expressed in this Society, that 

 we waste an enormous amount of water. We throw into 

 a stream without compunction impurities which will destroy 

 the value of many hundred times, or perhaps thousand 

 times, their bulk ; and this evil may, to a certain extent, 

 be cured with our present knowledge. We try in vain to 

 take out that which we have thrown in. A large part of 

 the evil can be cured by little trouble, although I confess 



