436 THE SALMON RIVERS OF SCOTLAND 



is often intensified. If you wish to maintain your river -banks and croys in 

 good order at a small cost, never postpone repairing any damage you may notice, 

 but have it put right as soon as possible. A little care at the time will save 

 much future labour. 



The pressure which a croy has to withstand depends on the surface it presents 

 to the stream and the angle at which the water strikes it, therefore it should 

 not be higher at any point than absolutely necessary, and in a strong current it 

 is better to extend it from the bank in a down-stream direction. This is more 

 especially the case with wooden croys which have not the protecting slope of a 

 stone apron, for when they stand at right angles to the stream they have to 

 sustain the weight of a belt of comparatively still water formed above them by 

 the rebound of the current before it takes a new course ; while if their direction 

 be slightly downwards, they guide the water without holding it up. 



The eddy that is apt to form behind a croy must be taken into consideration. 

 It is caused by the stream that runs round the point of the structure impinging 

 on the edge of the still water sheltered behind it, with the result that along the 

 line of impact swirls with a reverse motion are set up, and their accumulated 

 action induces an up-stream current near the bank, which may be strong if 

 there is any considerable depth of water at the place. To mitigate this effect, 

 short and low croys, even if you have to build more of them, are better than 

 long and high ones. 



We are aware that stones placed in the water to afford resting-places for fish 

 have proved satisfactory in some rivers, but our experience is that, except in 

 rapid streams, they generally collect gravel instead of salmon. Stones of 

 moderate size are better than large rocks, which limit a salmon's range of 

 vision, and interfere with his view of a fly or bait till they have passed. Small 

 stones, however, on a smooth shallow, may help the angler by causing a 

 deceptive ripple. 



