of the FIs/n.'/'i/ Hoard fur Scutlatnl. 



The fish pass at Mor[)hiL', although at lirst sight [nvst'iiting consider- 

 able similarity, will be foiiiul on ni(jre careful study to be in striking 

 contrast to that at Craigo. The dissimilarity in these passes lies 

 principally in their position and in the heights which they have to over- 

 come. The Morphie fish pass is 44 feet long, 5 feet wide, and rises 4 

 feet. As in the case of tlie fish pass at Craigo the gradient is steepest 

 at the upper end. No sto[)s are shown in the })lan made by Mi-, Sim, 

 nor was I able to see whether there were any, as water was flowing 

 through the pass when I inspected it ; but from tiie photograi)h taken in 

 1882, which is a[)pended to Mr. Sim's plan, it would seem that there 

 are, and that they are very similar in size to those in the fish pass at 

 ( 'raigo. The upper sill of the pass is 1 foot 9 inches below the crest of 

 the dyke. 



The dyke is V shaped, the angle of the \/ being placed up stream, and 

 either arm extending down stream for about three hundred and seventy 

 to three hundred and eighty feet, until they touch the banks of the 

 river on either side. The fish pass is placed on the north arm, about 

 twenty-five feet below where it joins the south arm, and the stream 

 from the mouth of the pass is poured right across the channel formed by 

 the dyke at a point where it is not more than fifteen feet across, so that 

 salmon ascending the river are led by the converging arms of the dyke 

 right up to the entrance of the pass. 



It has been pointed out that the entrance to a fish pass should be so 

 constructed that the greater body of water passing over the crest of the 

 dyke flows from the foot of the pass, as the power of a fish pass to 

 attract salmon is in proportion to the volume of water discharged from 

 its lower end. The Morphie fish pass, from its exceptional position, is 

 an admirable illustration of the application of this principle. The en- 

 trance to the pass practically begins at the point where the arms of the 

 dyke touch the banks of the river, and embraces therefore the whole 

 natural channel. From this point the pass may be said to gradually 

 contract in size, and the volume of water pouring down it at the same 

 time to diminish. But although it diminishes, it forms always the main 

 stream, and ofl'ers, therefore, a natural and attractive passage for 

 salmon. 



The actual construction of the fish pass proper seems to me to offer 

 no point worthy of imitation. On the contrary, the greater ease with 

 which salmon ascend Morphie than Craigo fish pass is, in my opinion, 

 due (1) to its position ; (2) to ^the lower height of the dyke ; and (3) 

 to the shape of the dyke. It is owing to the pass being placed across 

 the general direction of the stream that the water flowing over the dyke 

 strikes the water flowing down the pass at an angle, thus checking its 

 velocity and creating comparatively quiet water on the sheltered side of 

 the pass, in which the fish can ascend without difficulty. It is perhaps 

 superfluous to point out that, other things being equal, the lower the 

 dyke the less obstruction it presents to the passage of fish ; and it is 

 owing to its shape that, while the water level fluctuates comparatively 

 slightly in the pool above, it rises very quickly at the foot of the dyke, 

 so that even in a moderate flood the difference of four feet shown in 

 Mr. Sim's plan between the level of the water above and below the 

 dyke is reduced by about one half 



It would seem to me therefore that Morphie fish pass not only pos- 

 sesses an attractive entrance in a proper position, but affords as easy a 

 passage for salmon as is possible in a pass of that description. Their 

 passage would, howevei-, be still further facilitated if subsidiary dams. 



