THE FRESH- WATER LOCHS OF SCOTLAND. 159 



east to west exceeding a mile, the maximum breadth being two-thirds of 

 a mile. The superficial area exceeds 300 acres, or nearly half a square 

 . mile, and the drainage area is large exceeding 17 square miles. The 

 maximum depth of 49 feet was recorded comparatively close to the east 

 shore, whence the water shoals gradually towards the west, the western 

 portion of the loch being very shallow ; nearly GO per cent, of the entire 

 lake-floor is covered by less than 10 feet of water. The volume is estimated 

 at 192 million cubic feet, and the mean depth at nearly 15 feet. The loch 

 was surveyed on October 10, 1903, when the elevation was 1045*0 feet above 

 sea-level, as compared with 1045'8 feet determined by the officers of the 

 Ordnance Survey on August 16, 1866. The temperature of the surface 

 water was 49-l Fahr. 



Loch Phitittlais (see Plate LX.), a small but relatively deep loch, lies 

 less than 2 miles north-east of Aviemore, and about 3 miles north-west 

 from Loch Morlich. The loch is over half a mile in length from north 

 to south, and a quarter of a mile in maximum breadth, covering an area 

 of about 67 acres, and draining an area of about 2J square miles. The 

 maximum depth of 74 feet was observed approximately near the centre 

 of the loch, but towards the northern end, the basin being simple in con- 

 formation. About 69 per cent, of the lake-floor is covered by less than 

 25 feet of water. The volume is computed at 67 million cubic feet, and 

 the mean depth at over 23 feet. The loch was surveyed on October 12, 

 1903, when the elevation was found to be 674*3 feet above the sea; the 

 Ordnance Survey map gives the elevation as 673*9 feet, but the date when 

 levelled is not indicated. Temperatures taken in the deepest part of the 

 loch showed a range from surface to bottom of only J Fahr. : 



Surface 50-0 Fahr. 



10 feet 49-8 



20 49-8 



30 49-6 



40 49-6 



50 49-4 



70 ... 49-4 



Loch Builg (see Plate LXI.) lies nearly 20 miles east of Aviemore, 

 and about 6 miles north-west from Balmoral castle, in a valley running 

 north and south between Glen Avon and the head of Glen Gairn. A 

 small proportion of the overflow finds its way into the river Gairn, and 

 thence into the river Dee, as already stated ; but the normal outflow is to 

 the north, by the Builg burn and the river Avon, into the river Spey. 

 The reader is referred to the paper by Drs. Johnston and Collet, already 

 cited, for some remarks on the formation of Loch Builg. The loch is less 

 than a mile in length, by a quarter of a mile in maximum breadth, the 

 superficial area being about 77 acres. The maximum depth of 86 feet was 

 observed approximately in the middle of the loch. The volume of water 



