Mode] showing Salmon in different stages of progress to maturity, p. 183. 



EXPLANATION. 



A Water supply from cistern, constantly running. 

 B Plate-glass tank, containing artificially produced salmon fry. 

 c c Pipes conducting water out of tank to model below. 

 D D Troughs in which ova are being hatched, filled with clean gravel. 

 E E Gratings through which water passes to gravel. 

 G Model of river containing salmon fry. 

 H Weir across river. 



M Fish-pass over weir, to enable the fish to ascend to the upper waters without 

 interfering with the water power above. 

 K River below weir. 



