MIDDLETHIRD HATCHING-HOUSE. 



115 



WOOD FILTER 



inside the house to receive and divide the water used in hatching 

 (Fig. 61) ; it held three screens, and the water was dammed back 



-2' 9" 

 FIG. 61 scale fo. 



by an overflow-board to secure a full supply to the slate filter, all 

 passing the overflow being divided equally between the two 

 wooden hatching-boxes. This box proved successful ; Fig. 62 

 is a section. The principal ad- 

 vantage is that it never freezes 

 up, as the depth is sufficient to 

 allow the water to pass below 

 any ice likely to form during 

 the night, while, the screens 

 being some distance below the 

 top, when the first one clogs, 

 the water merely runs over its edge on to the second, and so on. 

 The importance of this is apparent when it is remembered that the 

 water off for a single hour may mean the loss of the ova or fry in 

 all the trays below. Should taps be used for regulating the 

 supply, an overflow must be fixed, over which a constant run 

 must be kept, else the flow from the taps will not be regular. 

 One of the most important points to attend to in fish-culture, 

 and one of the most difficult to attain, is perfect control over 

 the supply. Perfect regularity of supply, whether the source 

 from which it is drawn is in flood or low, whether the leaves 



-/' 8" 



Fio. 62 scale . 



