166 FISH CULTURE. 



transferred from the large lake of Boilsfut to that of 

 La Hulpe, forty-five jack, averaging one with another 

 two pounds each ; none of them weighing more than 

 three pounds. In eighteen months from the time 

 when they had been thus transferred, many of these 

 same fish were caught by trolling, having attained 

 the weight of from fifteen to twenty pounds, being at 

 the extraordinary rate above mentioned. 



" This increase in the size of the jack was so sud- 

 den and unexpected, that nearly all the smaller fish 

 were destroyed by them, before any steps could be 

 taken for their removal. It was, however, then effected 

 by letting out the water, when the jack were placed 

 in one of the smaller ponds above mentioned. In 

 this however, although it contained a good supply of 

 white fish, they rather lost than gained weight, pro- 

 bably, as Mr. Maltby imagines, in consequence of 

 there being a smaller body of water running through 

 it, and that colder, from being nearer the source. 



" At the commencement of the year 1 857, he had 

 purchased and turned into the lake at Boilsfut nine 

 hundred carp of a particularly good breed, weighing, 

 one with another, a pound each ; but of these, when 

 the water was let out in the month of October, not a 

 single one was to be found, the jack not having 

 suffered a solitary individual to escape them. Since 



