self-evident as the actual pollution of the rivers. It is this : 

 " Is a river contaminated by sewage dangerous to fish 

 life ? " 



The answer to this question should run thus : The ex- 

 tent and volume of the pollution must be taken into 

 account. Take a parallel case. It is pretty generally 

 known that lime water is inimical to fish life ; a fish put 

 into lime water dies immediately ; but take a small quan- 

 tity — say, two ounces of quicklime — and place it in a 

 river well stocked with fish, and you will find no result 

 from so small an amount ; then gradually increase the dose, 

 and you will arrive at the weight of quick lime that will 

 kill all the fish in the nearest pool to where the quicklime 

 has been put in. And so on, if you put a very large quan- 

 tity into the river you would for miles kill all the fish it 

 contained. I remember, some years ago, out of spite, a 

 very large quantity was put into an Irish river, and for 

 miles every fish was killed. Now apply this simile to 

 sewage pollution : put a delicate fish into raw strong 

 sewage, and he will very soon die ; yet a small quantity 

 of sewage allowed to run into a river has no effect, but 

 the moment you pass the amount the fish can withstand 

 they will become sickly and eventually die. From the 

 meeting at Hereford you will have noticed that at dis- 

 tances remote from the actual source of contamination, 

 no damage occurred to the fish in that part of the river, 

 although below the sewage inlet. How is this .'' The 

 solution of this difficulty may be thus explained : Rivers 

 are supposed to have the power of cleansing themselves 

 after their polluted waters have travelled a certain distance, 

 although this inherent power is valuable only so far as the 

 fish are concerned who inhabit the part of the river jDcrhaps 

 thirty miles below the source of pollution. Of course, this 



