MIDDLETHIRD SAFETY SCREEN. 



95 



enough to retain the fry. The pond was set in the course of the 

 little burn at Middlethird. All flood- water was diverted, and the 

 supply obtained through a leaf-screen, and quite regular. I 



K 1-'. g?*'----*--- 3 



thought everything safe, and was astonished to find the fry in 

 numbers dead against the outlet. They had hatched irregularly, 

 and were what I should now call a bad lot. They could not keep 

 ofF the outlet, so it was necessary to reduce the strength of the 

 current. I did not like to lessen the supply, and I placed a bank 

 of fine gravel right across the pond. This made matters worse ; 

 the fry burrowed through the gravel, and died against the outlet 

 as before. I then invented the 



SAFETY-SCREEN. 



It answered perfectly, and since then has, in one form or another, 

 been in constant use. The screen is only a rectangular frame of 

 light wood, on which is stretched No. 9 perforated zinc. This 

 size seems large, but is safe, much more so than a smaller size. If 

 any part of the yolk-sac slips through, the fish can draw it back 

 without damage. With small-holed zinc death is always the result 



of the yolk-sac coming in ^ i-'-e 



contact with the zinc, as 



once the smallest bit is sucked 



through, the rest follows from 



the pressure of the current. 



Fig. 40 is a drawing of the FIQ. 40 scale &. 



safety-screen now in use in the hatching-house at Milnholme. 



The safety-screen is fixed 13 inches above the outlet by a strip 

 of flannel doubled and passed round so as to jam the screen 

 tightly to the pond. Nothing else will do so well as flannel ; the 

 fry seem to hate it, they will not go near it, and never try to escape 

 under the safety-screen. If sand is placed in front of the safety- 



