How to obtain it. 157 
Where any fresh concrete work comes in contact with the 
water I prefer running the latter over it for three months. Cement 
is partially soluble, and in some waters more than in others. The 
soluble portions are injurious to trout ova, but after being in use 
for some time the whole becomes thoroughly seasoned, and is 
then quite harmless. I am alluding now to such works as settling 
tanks and aqueducts, for which concrete will often be found very 
useful. It is a very good plan, after the water has been running 
over new works for a few days, to turn it off and give the whole a 
good scour out, and after a few more days repeat the process. 
After this turn on the water for good, and do not on any account 
scour out again. Nature usually provides a coating for concrete 
work in the shape of minute vegetable growths, and these should 
not be thoughtlessly removed. The same applies to concrete 
ponds, with the exception that sometimes confervoid and other 
growths begin to threaten trouble. They may then be gently 
raked off or otherwise partially removed, but without any scraping. 
The well-known proverb, ‘‘Do nothing rashly,” certainly 
applies in fish culture, and it is well to observe it. It often 
happens that mistakes are seen when too late, which by a little 
forethought might have been avoided. 
A day or so before spawning a sufficient number of grilles 
should be placed in position for receiving the ova. They are 
usually stacked away in some convenient place, and are all ready 
for use. Dust them if they require it, and wash them well before 
placing them in the hatching boxes. It is well to keep them 
submerged in some tank for a few days, and finally to wash them 
under a tap. They are then ready for work and may be placed 
in position. On putting them into the hatching boxes let one 
side go right to the bottom, and shake them gently. This causes 
the glass tubes to fill with water. Then, without taking them out, 
lay them on their rests. They have a tendency to float at first ; 
but this is easily counter-balanced by placing a piece of lead on 
each end of the grille. These weights may be fixed or loose, and 
I prefer them loose, and use neat little cubes of lead specially cast 
for the purpose. Small blocks of stone will do perfectly well, or 
even stones out of a brook. 
When a box is commenced with it should always be filled 
