[5] FISH CULTURE IN CENTRAL EUROPE. 543 



which has been brought thereby winds and showers ; it is therefore a 

 common practice to keep these objects out of the water by means of 

 gratings and chains, or similar contrivances, even in cases where the 

 water is not to be used for such delicate objects as the hatching of fish. 

 But water invariably contains other particles, principally belonging to 

 the mineral kingdom, which remain floating, as their weight is very 

 light, and which are sometimes so diminutive that they can not be dis- 

 cerned with the naked eye, the water being to all ap})earances per- 

 fectly clear ; and it is these particles which, if allowed to remain in the 

 water for any length of time, cover any objects submerged iu it with a 

 sediment. 



The best authors on the subject of fish -culture state that this sedi- 

 ment is injurious to the eggs of fish. Max von dem Borne does not 

 hesitate to say that, next to mold, this sediment is the most dan- 

 gerous enemy of fish ; and Benecke, not satisfied to call attention to the 

 dangers of this sediment, accurately describes the means by which it 

 can be removed, and states that even the clearest water will always 

 contain some of it.* Hence filters are used, which I do not deem it 

 necessary to describe here, as they are well known, and have been de- 

 scribed in many treatises on the subject, the object of which filters 

 being to remove by mechanical means many of the small impurities, 

 sediment, and diminutive animals. Prof. P. Pavesi also attributes the 

 mortality which several times made sad ravages in the hatching-houses 

 of the fish-cultural establishment of Torbole to the lack of filtratiou.t 



The theoretical knowledge which I possessed, and the practical knowl- 

 edge derived from experiments made at Torbole and Garda, caused me 

 to start on my trip to foreign countries with the firm expectation that 

 I would find filters universally adopted. But my surprise was great to 

 find their use not near so general as I had supposed, and that they 

 were entirely wanting even in establishments where the quantity of 

 sediment had for a long time formed the cause of serious complaints, 

 as, for instance, at Hiiningen. In consulting the historical notice of 

 this establishment I found that the turbid character of the water of the 

 Rhine was deplored, and the wish expressed (in 1862) that filtering ap- 

 paratus might be introduced, which was entirely wanting; and that 

 then, as now, the water from some neighboring ponds was used for the 

 hatcheries, because the Rhine water contained so much sediment. 



In only five of the fourteen fish-cultural establishments which I vis- 

 ited did I see filtration properly practiced, namely, at Seewiese,*Ber- 

 neuchen, Wilthen, Michaelstein, and Velp, and a rudimentary filtra- 

 tion at Dachsen and Selzenhof. At Zurich the water of the lake is led 

 into reservoirs for public use, and is sufficiently filtered for that pur- 



* B. Beuecke : Fische, Flscherei und Fischeucht in Out- und West-Preuasen, Kunigs- 

 Jberg, 1881, p. 459. 



tP. Pavesi: Esgqeifigne Intemqzipnale dipesca aBerl'mo, Rome, 1883, p. 105. 



