28 BATHYMETRICAL SURVEY OF 



places a steep off-shore slope is indicated by the soundings, as, for instance, 

 off the western shore of the longer arm towards the southern end, where 

 a sounding in 55 feet was taken about 40 feet from shore, and a little 

 farther north off the same shore, where a sounding in 24 feet was taken 

 about 30 feet from shore ; again, off the western shore of the shorter arm, 

 towards the northern end, a sounding in 57 feet was taken about 60 feet 

 from shore. The approximate areas between the consecutive contour lines, 

 and the percentages to the total area of the loch, are as follows : 



Feet. Acres. Per cent. 



Oto 25 265 ... 42 



25 50 183 ... 29 



50 75 ... 146 ... 23 



75 ,, 100 . ( 33 ... 5 



Over 100 .' 5 ... 1 



632 100 



These figures show that the deep water is not of great extent, more 

 than 70 per cent, of the lake-floor being covered by less than 50 feet of 

 water, and more than 40 per cent, by less than 25 feet of water. 



Temperature Observations. The following serial temperatures were 

 taken in the deepest part of the loch, at 4 p.m., on September 6, 1902 : 



Surface 56-l Fahr. 



25 feet 55-6 



50 55-3 



100 54-7 



These observations show a range of only l-4 throughout the 100 feet 

 of water. 



Seiche. A seiche was observed at the west end of the loch, having an 

 amplitude of three-sixteenths of an inch, but the period could not be 

 determined. 



Loch na Claise Fearna (see Plate X.). Loch na Claise Fearna is 

 a little irregular loch lying about half a mile from the southern shore 

 of Loch Laxford, into which its outflow is carried by the Allt na Claise 

 Fearna. It is about midway between Laxford Bridge and Scourie, the 

 road skirting its eastern shore. In outline it is subtriangular, with the 

 apex pointing in a north-east direction, and covers an area of about 

 34 acres, while the area draining into it is nearly 1\ square miles. The 

 maximum depth of 38 feet was observed near the middle of the loch, 

 between the large central island and the northern shore. The volume 

 of water is estimated at 20 million cubic feet, and the mean depth at 

 13J feet. The loch was surveyed on September 10, 1902, when the 

 elevation of the lake-surface was found to be 135-0 feet above the sea. The 

 western and southern parts of the loch are shallow, the deeper portion 

 (exceeding 20 feet in depth) lying to the north and east of the large 

 central island, and covering an area of about 6 acres, or 1 7 per cent, of the 

 total area of the loch. 



