of the Fishery Board for Scotland. 



255 



Messrs. Davidson, Mugiemoss, the Messrs. Crombie, Grandholm, Mr. 

 Paton of Grandliome, and the District Fishery Board, was embodied in and 

 received Parliamentary sanction in the form of the " River Don (Salmon 

 Fisheries) Order Confirmation Act, 1910 " ; and under the provisions of 

 that Statute the undernoted works have now been executed : 



1. At the Stoneywood Dyke the old fish pass has been built up, and a 

 new fish pass 15 feet wide and 20 inches deep, measured downwards from 

 the average level of the crest of the dyke, has beoii constructed, com- 

 mencing at a point measuring from the westmost margin of the fish pass 

 30 feet from the corner of the heck at the intake of the Stoneywood Upper 

 Lade. The pass descends first at right angles to the line of the crest of 

 the dyke at the point of commencement, and then curves round more 

 towards the centre of the river to the toe of the dyke. It consists of 

 three pools, each three feet deep, measured from the crest of the partition 

 wall immediately below it, these walls being constructed of reinforced 

 concrete. The total length of the pass is about 60 feet, and the fall from 

 the sill at the upper end of the pass to the sill at the lower end is repre- 

 sented by the difference between 92*01 and 87 '67 o.d. 



Under the provisions of the Act of Parliament, the millowners are 

 bound to keep the fish pass running at its full capacity at all times when 

 there is sufiicient water in the river for that purpose. 



The millowners' rights of abstraction were also settled by the Agree- 

 ment and subsequent Act of Parliament, and the other works carried out 

 at Stoneywood were designed for the purpose of automatically regulating 

 such abstraction in accordance with the terms of the arrangement come 

 to amongst the various parties. 



That purpose has been efiected^by^the construction in the upper lade 

 at Stoneywood, commencing near its intake at the Stoneywood Dyke, of a 

 weir wall 400 feet long, separating the lade proper from a spill water 

 channel formed to receive such water as overflows the weir wall when 

 the conditions in the river are such as to afford a sufficient supply for 

 that purpose. 



The Agreement between the parties, as indicated above, was that no 

 water was to be abstracted from the river until the fish pass was running 

 at its full capacity, unless in certain specified exceptional circumstances, 

 that thereafter the Messrs. Pirie were to be allowed to abstract a certain 

 specified quantity of water, but no more, except such as was due to the 

 increased head of water in the lade, until water to a depth of 6J inches, 

 measured fromi the average height of the crest of the dyke, was passing 

 over the Stoneywood Dyke, and that thereafter they would be entitled 

 to abstract one half of any excess of water flowing down the river over the 

 quantities already specified. 



The automatic regulation desired has been effected by leaving in the 

 weir wall an orifice of dimensions calculated to pass, when the water is 

 lipping the crest of the dyke and the fish pass would consequently be full, 

 the defined quantity of water that the millowners are, by the arrange- 

 ments, entitled to abstract under these conditions. The weir wall itself 

 has been constructed, after experiment, at such a level as to prevent any 

 water passing over it until the stipulated depth of 6| inches is passing over 

 the crest of the dyke. The water spilling over the weir wall falls into the 

 spill water channel, which is really a widened portion of the lade, and so 

 finds its way to the turbines. 



In order to provide for exceptional circumstances arising from natural 

 conditions, a snow sluice is provided in the lade immediately before the 

 weir wall commences, and in the weir wall itself there is an emergency 

 sluice capable of passing a modified quantity of water for use under 

 certain specified exceptional circumstances. 



