40 THE FISHERIES. 



If, when the mill is at work, waste-water is escap- 

 ing in quantity over the weir, in the usual flow of 

 the river, the construction of a '' salmon-pass " will 

 be in such case comparatively easy. Nothing more 

 will be required than to build against the weir, on 

 the down-stream side, an inchned plane at a proper 

 angle of inclination — say, with a gradient of about 

 one in twenty, commencing below the apron of the 

 weir at bottom, and finishing at " nothing " at the 

 crest; if this superadded structure be sixteen or 

 eighteen feet in width, built of hammered stone, 

 slightly concave on the surface, without stops to col- 

 lect the water (which only impede the fish) and so 

 placed, in the river, as to face the channel of a cur- 

 rent on the down-stream side, it will afford an easy 

 and suitable passage for salmon : the fish will spee- 

 dily become acquainted with it : with about three 

 inches of water going over the weir they will ascend 

 it readily, but in flood time, and in little freshes after 

 rain, they will dash over it with as little concern as 

 if no weir at all existed at the place. 



There is another class of weir, which we may call 

 the V weir, being in the shape of that letter inverted,, 

 the angle pointing up-stream ; here, under the same 

 conditions, that is, waste-water passing over the weir 

 when the mill is at full work, a pass can with much 

 faciUty be constructed, by forming the inclined plane, 

 with concave surface, before referred to, at the same 

 angle of inclination, commencing with its centre at 

 the apex of the V, and terminating at the outer edge 



