520 REPORT OF COMMISSIONER OF FISH AND FISHERIES 



it should also strive to utilize all refuse matter in as complete aud satis- 

 factory a manner as possible. 



It is a fact whicli can be observed everywhere that nature utiUzes 

 refuse matter of different kinds in such a manner as not to injure deeper- 

 lying springs, that is, the upper layers of soil or rock absorb the refuse, 

 either changing its character or forcing it to enter other combinations, 

 so that in both cases the lower strata receive but very little of it. This 

 purifying process, which is going on on an extensive scale, is both of a 

 mechanical and chemical nature, and presents the best and simplest 

 starting-point for discussing this whole question. 



PURIFICATION OF WATER BY REPOSE. 



The success of this purifying process is very clearly demonstrated by 

 the glacier water flowing from lake to lake. In a turbid and milky 

 condition the icy water leaves the mountains on its way to the plain, 

 till it enters a lake often of very considerable depth aud extent. Al- 

 though the same quantity of water leaves the lake to continue its jour- 

 ney towards the j)lain, it comes out as clear as crystal, whilst long banks 

 of clay or sand gradually mark the entrance of the turbid glacier water. 

 The same observation may be made in rivers. A strong current carries 

 all the floating particles of clay and sand far down the river, while a 

 sluggish current allows them to gather in the bed of the river or on its 

 banks, thus purifying the turbid waters. An attentive observer may 

 watch the same process in every brook ; wherever an indentation of the 

 bank delays the rapid flow of the water, numerous particles of mud will 

 gather, and many substances injurious to the life of fish are in this way 

 removed from the water. This natural process of j)urifying flowing water 

 by allowing it to enter a condition of repose can easily be imitated in an 

 artificial way, and should be adopted wherever turbid water enters brooks 

 and rivers. 



This is particularly the case in the neighborhood of mines, quarries, 

 factories, for instance, beet-sugar factories, &c. It will suffice in every 

 case to construct so-called "mud-catchers" — ponds through which the 

 turbid water is led. If the water, as is often the case in mines, flows out 

 with the strength of small brooks, 2 to 3 ponds should be constructed, 

 one by the side of the other, regulating their depth according to the 

 quantity of impure matter in the water. It will also be well to cultivate 

 in these ponds aquatic or floating plants or reeds, aud to plant willows on 

 their bauks, as such vegetation aids the purifyiDg process in more ways 

 than one. I have often observed that by simply following these rules a 

 single pond proved sufficient to purify comj)letely the turbid water flow- 

 ing from a mine. In such a pond hardy fish, and even carps, were 

 raised. 



From time to time the pond would yield a great quantity of mud, 

 which, when taken out during the cleaning of the i^ond, proved a valu- 

 able fertilizer. 



