THE FISHERIES. 41 



of the apron of the weir; in this angular description 

 of weir, a pass so constructed will be highly efficient ; 

 the water doubling itself at the apex, which is the 

 most difficult part, will give additional facihty of pas- 

 sage, and the concave surface collecting it below will 

 form a sufficient " lead." The salmon will seek it 

 and pass over without difficulty — in time of fresh, or 

 flood, or in the weekly close-time when the mill stops 

 work, this weir, with the above alteration, will pre- 

 sent little or no obstruction. 



The devices above indicated assume that waste- 

 water is escaping over the weir in some quantity, at 

 all seasons when the mill is at full work — but this 

 condition cannot always be fulfilled; in some streams, 

 and at some weirs, the mill takes the whole of the 

 water, and the weir is dry, or nearly so, during the 

 greater part of the summer. It is a mistake to ap- 

 ply any description of pass to every description of 

 weir : give a salmon water enough, and he can do 

 almost anything ; but to build a migratory pass, 

 where the chief element is absent, will be only as 

 futile as the plan or specification which proposes it. 



We therefore, now assume the worst case : let 

 the problem be to make an efficient migratory pass 

 where no water at all escapes over the weir, in an 

 average state of the river, when the mill is working. 

 This object, we allege, cannot be attained by any of 

 the plans officially propounded, until salmon can be 

 found to advance up an inchned plane in any other 

 element than water — and building the pass will not 



