[5] EEPOPULATING BELGIAN WATERS. 819 



weiis or dams which lay dry for a time a portion of the bed; (7) regu- 

 latiug- the sizfe of meshes so as to allow all fish measuring less than 15 

 centimeters to escape from the nets; (8) establishing- salmon-ways 

 wherever obstructions exist of such a nature as to prevent the migra- 

 tion of fish ; (9) prohibition of fishing with the hand, &c. ; (10) meas- 

 ures to prevent as much as possible the pollution of the waters by 

 manutactures established on their banks; (11) serious efforts at organ- 

 ized fish-culture; (12) committees of surveillance, furnished with the 

 necessary authority to prohibit fishing locally and temporarily, in the 

 interest of the repopulating of the rivers. 



In the following year (1880) M. Gens was commissioned by the Gov- 

 ernment to visit the Berlin Fishery Exposition, and attend the Piscicult- 

 ural Congress which oi)ened its sessions in that city in April. His re- 

 port was published in the Moniteur beige for September 19, 1880. 



Our honored colleague M. Raveret-Wattel has in the Bulletin Mensuel 

 (Ic la Societe d.Acclimatation de France produced such an excellent and 

 (;on)i)lete work that I deem it unnecessary to give an epitome of M. Gens's 

 work on the same subject. I will confine myself to pointing out some 

 of its details. The author mentions the fact that several essays had 

 been written on the problem of rendering the water from manufactures 

 harmless to the fish in those parts of the river where such waters are 

 emptied. It is well knowu that the King of Saxony had set a prize for 

 the answer to this question, which is of great interest to us in Belgium. 

 M. Gens also mentions a simple means, which had been spoken of at 

 the congress, of rendering small water courses, such as those which 

 drive mills, pure. If the dam is constructed ou an inclined plane, it is 

 sufficient to place a beam obliquely across this place, which is certainly 

 inexpensive, and should be done in all cases. In chapter 4 he takes u]) 

 the i)rinciples laid down in his pamphlet of 1879, mentioned above, and 

 supi)lements his former statement by giving a list of nearly all fresh- 

 water fish found in Belgium, which he, according to their nature, 

 classes in three groups: those which are common to our two regions, 

 those which are found in the mountainous region, and those which are 

 found in the plains. 



In a special chapter M. Gens treats of piscicultural establishments. 



Belgium did not possess a large sheet of water combining purity, cold- 

 ness, and depth, where it might be hoped that the salmonoids of the 

 Swiss lakes could be acclimatized. Today this is diflerent. In order to 

 check the temporary inundations of the Vesdre, and at the same time to 

 supply water to the city of Verviers, which at certain seasons suflered from 

 the want of it, there has been constructed from one mountain to the 

 otlier, near the mouth of the Gileppe, at the height of 241 meters above 

 the level of the sea, a gigantic dam, 47 meters in height, which when 

 filled tolds 12,000,000 cubic meters of the waters of that sub- Alpine 

 river, which receives all wh.ch flows into tliis dam from a forest of 

 about 4,000 hectares called the "Hertogenwald," and from the marshy 



