THE THURSO 247 



about 13 miles, being 9 miles west of the river mouth, the important 

 direction as, I believe, and 4 miles east of the river mouth. 



Another important step has been taken in erecting at the outlet 

 from Loch More, a dam dyke and fish pass. The dam dyke raises 

 the level of the loch 12 feet, the purpose being to impound such a 

 quantity of water as will enable artificial floods to be let down the 

 river at will. This action has been taken in view of the success of 

 the dain dyke built on the Helmsdale at Badanloch. In future, there- 

 fore, when the Thurso runs too low, when fish become a little stale 

 from lying long in one pool, or when fish off the mouth of the river 

 are unable to ascend, a flood will be let down of sufficient volume to 

 create good " running-water," fish will be moved from pool to pool 

 and will be drawn into the river from the sea. The system 

 employed may now be regarded with some degree of confidence after 

 the seven years' experience of the Helmsdale, and the much older 

 but similarly successful experience of " sixty-one," the pioneer of this 

 class of operation in the Lewis. l 



The dam and fish-pass were designed and constructed by Mr. P. 

 D. Malloch, Perth. The dam dyke is in the form of an obtuse 

 angle, the apex being at the natural river outlet. The arm of the 

 angle which runs to the right bank has a bye-wash overflow for 

 storm water ; the arm of the left bank is the longer of the two, and 

 has running alongside of it the gradually ascending fish-pass. The 

 angular design of the dam dyke is apparently in order to allow an 

 easy gradient in the pass. The wall at the angle of the dyke is 17 

 feet high, and the length of the main overflow is 310 feet. The fish- 

 pass is 200 feet long, 12 feet wide at the top, and 25 feet wide at the 

 bottom ; it has a gradient of 1 in 20. To act as breaks to the 

 descending water, rows of stones are erected at intervals and these have 

 since been modified, I understand, by the placing of wooden battens 

 against the stones. To allow of fish entering the loch when the level 

 does not permit of the highest part of the pass being filled, two 

 openings, or passages, through the dam dyke at right angles to the 

 direction of the pass are provided at lower levels. Each opening is 

 3 feet square, and is sluiced. During one of my visits to this pass, 

 the level of the loch was such that only the spray from loch waves 

 came through the upper of those square openings, while the lower 

 opening had 2 feet of water. In other words the loch was 

 practically half-way down the dam dyke. The 2 feet head of 

 water in the lower opening produced in the pass, in my opinion, a 



1 Twenty Years' Reminiscences of the Lews, 1871, p. 97. 



