of tlie Fishery Board for Scotland. 



19 



in a comparatively small pass, such breaks can be made of large boulders. 

 This I have seen done with excellent effect at Mr. Ian Nelson's pass in 

 Glen Etive, and I have since introduced it elsewhere with equally good 

 results. 



At the Kingairloch pass already referred to the sills of the pools are 

 slightly trough-shaped in addition to the alternating U — the sill at the side 

 opposite the U being higher than at the U. This seems to give a very 

 agreeable outflow, and I am informed by Mr. Strutt, of Kingairloch, that 

 although the whole structure has been in his opinion unnecessarily costly, 

 the pass works to his complete satisfaction. 



The Falls of Tummel Pass.— I may, suitably perhaps, include now a 

 short description of the large pass now almost completed at the Falls of 

 Tummel, and at the same time venture to mention wherein I consider the 

 arrangement might be still further improved. When finished, as I expect 

 it will be by the time this is published, it will rank with the Invermoriston 

 pass as the largest structures of the kind in Scotland. 



The height of the fall, as between the extremities of the pass, is 18 feet, 

 and the pass is constructed entirely through solid rock on the left or 

 Bonskied side. 



The length of the pass is 140 yards ; breadth, 10 feet ; gradient, which 

 is uniform throughout, 1 in 23. 



A tunnel has been formed, 40 yards long and 6 feet high, in the up- 

 stream half of the pass. The tunnel was completed on 23rd March, and I 

 walked through it a few days later. The quartzite rock is of extra- 

 ordinary hardness opposite the fall, and the open cutting of the lower 

 section of the pass attains a maximum depth of 37 feet. The Tay 

 District Fishery Board, who bear the expense of the pass, and who have 

 decided on its features, arranged that the floor of the pass should be formed 

 without pools, and that provision for the checking of descending water 

 should be adjusted by rows of stones as in the Loch More pass. The rows 

 of four stones are placed at intervals of 14 feet throughout the length of the 

 pass, the spaces between the stones being, roughly, 1 foot 4 inches. 



In a pass 140 yards long, as this is, and with a gradient of 1 in 23, 

 water would naturally become unduly rough in the lower half, in spite of 

 the rows of stones. To obviate this, it has been decided to restrict the 

 inlet of water so that a depth of 1 foot 5 inches will constantly descend the 

 pass, this being the depth at which it is considered the pass will best work. 

 The restriction at the inlet is regarded, however, as temporary and 

 experimental, and is being formed of wooden battens. These battens are 

 to be raised to a height of 6 feet 9 inches above the level of the sill, so as 

 to prevent the entrance of flood water. From what I have already said 

 under the heading of " Sluices at Waterfalls," it will be seen that, in my 

 opinion, more favourable conditions for the success of the pass would have 

 been secured if the inlet had been left open, but provided with an outer 

 protecting barrier as in Norwegian passes, and if pools with steep sloping 

 floors had been relied upon to check the flow of the water. I consider that 

 the restricted opening need not now be regarded as in an experimental 

 stage. It is exactly analogous to a partially-closed sluice. 



It is, however, matter for great satisfaction that a pass of a substantial 

 sort has been, at last, constructed at this important waterfall. The distance, 

 measuring above the Tummel Fall to the head waters of Loch Ba, and 

 to Loch na-Gannich, is between 50 and 60 miles, about one-half of which 

 consists of river with good spawning ground. Taking the more northerly 

 direction to the head of Loch Ericht, the distance is practically the same, 

 but only about 26 miles consist of river. With so extensive an area of 

 pure water and good spawning ground, the opening up of the fall in 

 question should, if the pass is successful, be of great value to the Tay 

 district. 



