132 Flow to obtain tt. 
Each hatching box must be provided with a screen, which 
consists of a charred wooden frame covered with perforated zinc 
(No. 7 zinc is a good size). This screen slides in a groove, made 
by cutting a strip out of the sides of the hatching box as shown by 
the dotted lines B c in Fig. 7. This groove is made, of course, on 
the insides of the box, and should be carefully charred. A piece 
of flannel should be placed between the screen and the box, and 
great care must be taken that it fits perfectly tight, and that no 
newly-hatched fish can get through anywhere. If it be by any 
means possible, most assuredly they will. Rests require to be put 
in along the insides of the box for the grilles. JI have tried many 
plans, but find nothing better than small galvanized staples, which 
take up little room, do not make corners into which the fish can 
Fig 4. 
get, and are not much in the way at any time, when not occupied 
by the grilles. They should be varnished. I have used inch 
wire nails driven in half of their length, but I like the staples 
better. 
All wooden hatching apparatus should be carbonized wherever 
the water comes in contact with it. Elsewhere it may be painted. 
The carbonizing, or charring as it is commonly called, is done by 
working hot irons over the surface of the wood. The bigger the 
iron the longer it keeps hot, but the greater amount of heating 
it requires to make it hot enough. It often happens that at a 
hatchery a very large fire is inconvenient, and therefore, it is better 
to have comparatively small irons. To begin with, procure from 
an ironmonger two of the largest ordinary “flat irons” that are in 
general use. They will be found to do the work well and are 
