How to obtain it. 



139 



security to the works, and is one of the first and most important 

 considerations in connection with a hatchery. 



For work on a small scale one of the most useful arrange- 

 ments is shown by Fig. 12. There are many modifications, but 

 the principle is the same. It may be worked against a wall as 

 shown, or out in the open, the boxes being supported by a wooden 

 frame. It may be inside a building or otherwise. One of the 

 most important points to be observed in its construction is that 

 the outlets are efficient. Be sure that they are capable of 

 conveying all the water that will ever be required, and take care 

 also that the screens are large enough. I have so often seen 

 screens made by simply nailing a piece of perforated zinc on to 

 the inlet end of a spout, that I feel it necessary to give this caution. 

 A very simple way of making a screen is to nail three strips of 

 wood, each of about six inches long, so as to form three sides of 

 a square enclosing the outlet, and nail the perforated zinc on to 

 them. I use these small hatching boxes occasionally for experi- 

 menting, and in my own I prefer to have the screen the full width 

 of the box, fitted as described for the larger boxes. The results 

 are much more satisfactory, as full-sized screens do not so easily 

 get clogged, and when the egg shells are about this is important. 

 There are other reasons also, which will be referred to in another 

 chapter. 



ii 



Fig. 12. 



