CH. III.] DESTRUCTION CAUSED BY LARGE JACK. 43 
contained a good supply of white fish, they rather 
lost than gained weight, probably, 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 1857, 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 that time Mr Maltby has 
allowed no Jack to be put into his water, as stock, 
above a pound in weight, which (as younger fish 
do not gain weight so fast,) will not increase in 
a year to more than about three or four pounds. 
It is only after attaining that weight that their 
growth becomes so astonishingly rapid. 
In the Lake at Boilsfut, Jack, Perch, and 
white fish breed fast, but the fish born in that 
Lake do not increase so fast by two-thirds as 
those born in La Hulpe; so that, although their 
transport from the one to the other is expensive, 
yet it is made up for by the increase of weight in 
the fish transported. 
