THE FRESH- WATER LOCHS OF SCOTLAND. 279 



by levelling; when visited by the Ordnance Survey officers on Sep- 

 tember 7, 1870, the elevation was 418'9 feet above sea-level. Its waters 

 cover an area of nearly 200 acres, or less than one-third of a square 

 mile, and it drains an area of nearly 4 square miles. The loch is on 

 the whole very shallow, with a deep hole in the north-eastern part of 

 the loch, in which two soundings of 35 feet were taken; except for a 

 neighbouring sounding of 22 feet, the remainder of the lake-floor is 

 covered by less than 20 feet of water, and all the western and southern 

 parts of the loch are less than 10 feet in depth. The volume of water 

 is estimated at 68 million cubic feet, and the mean depth at 8 feet. 

 Only 22 per cent, of the lake-bottom is covered by more than 10 feet 

 of water, and only 2 per cent, by more than 25 feet of water. At 

 5.15 p.m. on the date of the survey the surface temperature was 59'3 

 Fahr., and a reading at 27 feet gave 59-0. 



Loch Glass (see Plate LXIL). Loch Glass is one of the larger and 

 more important lochs within the drainage basin of the Cromarty firth, 

 and it exceeds in depth all the other lochs of the basin. It lies in a 

 mountainous district to the north of Strathpeffer, with Ben Wyvis and 

 other peaks exceeding 3000 feet in height to the south-west, and lesser 

 mountains to west, north, and north-east. It trends in a north-west 

 and south-east direction, but with a slight bend in the outline, causing 

 it to appear somewhat crescent-shaped. It is 4 miles in length, with a 

 maximum width near the centre of two-thirds of a mile, narrowing 

 gradually towards the south-east end, where the river Glass flows out, 

 the mean breadth being nearly half a mile. Its waters cover an area of 

 nearly 2 square miles, and it drains an area exceeding 25 square miles. 

 The maximum depth of 365 feet was observed nearer the north-west 

 than the south-east end, and towards the north-eastern shore. The 

 volume of water is estimated at 8265 millions of cubic feet, and the 

 mean depth at 159 feet. It was surveyed on August 26 and 27, 1902, 

 but the elevation of the lake-surface above the sea was not determined 

 by levelling ; when visited by the Ordnance Survey officers on September 

 1, 1868, the elevation was found to be 712*9 feet above sea-level. 



Loch Glass forms a simple basin, with very few minor undulations 

 of the lake-floor. The deeper water lies towards the north-west end, 

 and the contour-lines all enclose continuous areas. The 100-feet basin 

 is 2 1 miles in length, approaching close to the north-west end, but 

 distant nearly a mile from the south-east end. The 200-feet basin 

 is nearly 2 miles, and the 300-feet basin over a mile, in length, being 

 distant respectively 1| and 2 miles from the south-east end. The 

 soundings indicate here and there slight irregularities on the lake-floor, 

 and sometimes in very deep water. One of these gives rise to a curious 

 sinuosity in the 300-feet contour-line off the south-western shore, and 

 the sounding immediately to the south-west of the maximum depth of 



