THi: FRESH-WATER LOCHS OF SCOTLAND. 195 



water is reduced to about half a mile. The outline is extremely irregular, 

 and there are many islands large and small. The northern part of the 

 loch is somewhat triangular, but its centre is filled by three large islands, 

 the largest of which, Eilean Leathann, is fully half a mile long. 



As in Loch Scadavay, there are many distinct depressions, separated 

 by shallows. In each of these there is considerable depth. In the 

 narrow part, west of Eaval, there are three basins with maxima of 

 51, 57, and 50 feet respectively. South of Eilean Leathann is a basin 

 with a depth of 65 feet, and east of the same island one of 58 feet. North 

 of Eilean Leathann is a depth of 48 feet. Between Eilean Mor and the 

 stream flowing out to the north into Loch Eport lies the deepest basin 

 in the loch. It is of very limited extent, measuring only about a quarter 

 of a mile each way, between the islands and the shore, but has the 

 remarkable maximum depth of 151 feet. To the west of this is another 

 very small triangular area, having a depth of 70 feet. The mean depth 

 of 25f feet is less than that of Loch a' Ghlinne-Dorcha, and a little more 

 than that of Loch Crogavat, The greater part of the shore is of rock, 

 forming on the west a range of cliffs, with some small stretches of gravel, 

 stones, and peat. Immediately under the north slope of Eaval is the 

 largest stretch of peat-covered gravel, extending about a mile without 

 any exposed rock. The large islands, and most of the small ones, are 

 of rock. On Eilean Leathann mounds of stony debris lie over the rock. 

 The level was ascertained on June 15, 1904, by measuring from Loch na 

 Ceithir-Eileana to be 8*2 feet above the sea. 



Loch Obisary is tidal. Though the surface level is little affected by 

 the tides, these enter often enough to render the water quite salt, and to 

 permit numerous marine animals to live in it. Mussels (marine) were 

 found adhering to the fresh-water weeds, and marine Crustacea abounded 

 among the weeds. Large beds of a slender grass-like plant, which 

 appeared to be Juncus sujjinus, but was not in flower, reached the surface 

 from depths of from 14 to 18 feet. From the deepest part a black gritty 

 mud was obtained. 



A series of temperatures was taken in the deep hole at noon, June 25, 

 1904. There was a range of 8' '3, and a remarkable inversion was indicated, 

 the thermometer at 50 feet reading 1" lower than at the bottom. The 

 readings at 50 feet and 100 feet were repeated, after testing by again 

 reading the surface temperature, and were consistent with the first 

 readings : 



Surface (repeated) 55-5 Fahr. 



10 feet 55-5 



25 50 ? -4 



50 (repeated) 47^2 



100 (repeated) 48-2 



150 48-2 



Loch a 1 Chladaich (see Plate LXXV.j. A very small narrow loch on 



