278 Part III. — Ninth Annual Report 



Loch Ness. 



The first of these lochs to be examined was Loch Ness, which occupies 

 the eastern part of the valley. It is, with the exception of Loch Morar, 

 the deepest fresh- water loch in Britain. The deepest part of the loch is 

 in the vicinity of Foyers, and is, according to the chart of the Caledonian 

 Canal, 129 fathoms, or 774 feet deep. The surface of the loch is 50 feet 

 above the sea and the bottom is therefore fully 120 fathoms below sea 

 level, or deeper than the deepest part of the North Sea anywhere within 

 the British area except in the extreme north. It is 26 miles in length by 

 about 1 mile in breadth. 



From some apparently unknown cause angling for salmon in Loch Ness 

 is usually not very successful, not because salmon do not visit the loch, 

 for great numbers of them are kuown to pass through it on their way to 

 the river Oich, and thence to the Garray, that falls into Loch Oich, both 

 of which are excellent salmon rivers. The uniformly great depth of the 

 loch may be partly accountable for this want of success, for, with the 

 exception of about four miles at the east end and about two miles at the west 

 end, and a very limited portion along each side, no part of the loch is less 

 than 100 fathoms in depth. 



The dredge was first let dowu a little east of Castle Urquhart, where 

 the depth is given on the chart as 128 fathoms. A lining of fine gauze 

 was fixed to the inside of the net for the purpose of preventing the 

 smaller objects collected at the bottom from being washed out while the 

 dredge was being hauled up. The dredge reached the bottom easily, no 

 obstacle of any kind, such as under-currents, being encountered, and was 

 hauled up choke-full of fine mud ; mixed up with the mud were numerous 

 fragments of firm peaty matter containing pieces of partially decayed 

 wood. The contents of the dredge were emptied into a tub, and a careful 

 examination made of it. First, a quantity of the fine mud was put into 

 a bottle with water and allowed to stand till the mud subsided ; a distinct 

 stratum of flocculent matter was then observed on the surface of the mud, 

 this was shown by the microscope to consist wholly of the exuviae of 

 Entomostraca, chiefly of Cladocera. Second, a large quantity of the mud 

 was carefully washed through a fine muslin sieve, but though fragments 

 of Entomostraca were obtained in considerable abundance no trace of any 

 living organism could be detected. Third, some of the mud was dried 

 and then redissolved in water, and the floating matter carefully collected 

 and examined, but still no trace of any living thing — that is, no organism 

 that had been alive when the mud was brought up — could be observed. 

 The deep part (129 fathoms) in the vicinity of Foyers was also dredged 

 with the same results. 



It would seem as if the fragments of firm peaty matter referred to 

 were part of an older and more compressed portion, and the fine mud the 

 newer and continually increasing layer, of a deposit of peat that is 

 being formed at the bottom of the loch. If this supposition be correct, it 

 explains to some extent why living organisms, especially Entomostraca, 

 were so conspicuous by their absence in the dredged material from the 

 vicinity of Castle Urquhart and from the other parts of the loch exa- 

 mined. It has been proved that peaty mud is not a favourable habitat 

 for non-pelagic Entomostraca, more especially Ostracoda. 



Some Diatomacea were observed among the peaty ooze, but they 

 appeared to consist only of dead tests. 



Besides using the dredge, a tow-net was worked near the surface and 

 another at a depth of about 60 to 70 fathoms, and both nets captured a 

 considerable number of Entomostraca, including Bosmina, Cyclops, Daphnia, 



