288 SALMON FISHING 



either fish suitable for sport or newly-arrived gravid 

 fish seeking to go far inland. 



Of what design, then, is the ideal pass ? The diffi- 

 culties to be overcome not being uniform, there is no 

 single design that will meet all cases ; but the essential 

 principles have been discovered, and are capable of 

 being set forth by an example. When the passes at 

 Loch Vennachar are reformed they will constitute 

 a model system. The work is going on under the 

 charge of Mr. J. R. Sutherland, Engineer to the 

 Corporation of Glasgow, which draws part of its 

 water-supply from the lake. Mr. Sutherland has 

 kindly sent to me a copy of the design, which I 

 present on a reduced scale. A general explanation 

 of the principles embodied in a proper pass I give 

 in the words of Mr. Malloch, by whom, after much 

 expert thought, the Vennachar design was drafted. 



"Having taken a great interest in fish passes 

 during thirty years, and having inspected passes 

 all over the country, I came to the conclusion 

 that there was great room for improvement. After 

 several experiments, I found that I had overcome 

 all the defects of the existing passes. These experi- 

 ments I have put into practice, and I have found 

 them successful beyond my expectation. 



"The first important difference is that in my 

 passes the gradient is 1 in 20, instead of being from 

 5 to 10, as in most of the old passes. The Deanston 

 Pass, on the Teith, which is 1 in 27, is exceptional. 

 This came about somewhat by accident. The weir 

 was formed before the pass, and the weir was 1 in 27. 



