STREAMS OF THE OUTER ISLES 309 



when damming operations were carried out there. But in 

 both places the damming has been a distinct success. The 

 operations on the Blackwater were, ultimately so widely ac- 

 knowledged as successful, that similar operations were carried 

 out on neighbouring lochs. The Grimersta had a dyke, as it 

 is called in Scotland, or a dry-stone wall, as it would be called 

 in England, thrown across the outlet of each of its lochs. 

 These form only very imperfect impounding walls, but are 

 found to be sufficient. No sluices are used, even at Loch 

 Langabhat, which is 7 miles long, although here at one time a 

 grating was in existence to prevent fish running up too fast 

 and being lost in the large loch. The formation of the dyke 

 on the lowest loch carries a tale with it, which will be given 

 presently. At other lochs in the Lews the dams have now 

 been allowed to fall into disrepair and uselessness. 



A peculiar trouble sometimes is noticeable amongst the fish 

 which lie long in the shallow salt-water bays waiting till suitable 

 floods come for their ascent. It is locally described as the 

 White Spot, and has no connection with the ordinary salmon 

 disease. 



Through the kindness of Mr. George Pople, formerly tenant 

 of the Grimersta fishings, I received several specimens of fish 

 showing this peculiar ailment. When the streams become 

 sufficiently swollen after rain to admit of their ascent in fresh 

 water, " the white spot " disappears. The only reference to 

 this disease of which I am aware is in Scottish Moors and Indian 

 Jungles, p. 141, by Captain J. T. Newall, who was at one time 

 tenant of Scaliscro shootings, just south of Grimersta. It is as 

 follows : " The summer in the Lews in 1880 was remarkable 

 for the unusual heat. Salmon, in consequence, could not 

 ascend the rivers, which became so attenuated as to afford no 

 waterway for them. Fresh water being equally necessary as 

 sea for the health of the fish at the proper season, they suffered 

 in consequence. Many became quite blind, and developed a 

 white spot on the head, the result being the death of numbers 

 near the mouths of rivers." The natural inference is that 

 the lack of fresh water is responsible for this trouble. This 

 I consider very unlikely indeed. The blindness, the bright 

 sunshine of hot weather, the perfect translucency of the sea 

 water around these western islands, and the shallow nature of 



