190 



SEASON 1875-76. 



discharged into a waste channel, which returned the surplus to the 

 foot of the apron of the dam. 



A screw sluice closed the plank delivery-box from the water- 

 trap. This sluice had iron ties on its screw-nut, so that it could 



FIG. 141 scale 



be padlocked after being set (Fig. 141). The screw itself was of 

 thorn, a wood very suitable for the purpose, as it is easily cut with 

 the ordinary French screw-cutter, takes a clean edge on the worm, 

 and lasts for ten or fifteen years, even where unprotected. The 

 worm, on a stick 1^ inch thick and 2 feet long, can be cut 

 without a lathe in less than ten minutes. So easy and so useful 

 are these French screw-cutters, I would advise one to be marked 

 in the inventory of implements in every fish-cultural establishment. 

 Figs. 137-141 are diagrams of the intake works to the Howietoun 

 Fishery. 



When the dam and well were completed I filled in the tem- 

 porary channel, and built an overflow at the point where it had 

 left the stream. This overflow was faced with whinstone blocks, 

 and a beech overflow-board was laid parallel to the stream, and of 

 sufficient length to ensure that no flood ever rose more than 

 6 inches on its edge. As a matter of fact, up to the present date, 

 no flood has yet risen more than 3 inches on its edge. As the 

 ground fell, the mouth of the overflow was gradually contracted 

 to a neck, so as to save ground, and the course was led into the 

 old course of the stream some yards below the dam. The whole 



