THE FRESH- WATER LOCHS OF SCOTLAND. 79 



Feet. ' Acres. Per cent. 



Oto 25 57 ... 38-5 



25 50 39 ... 26-3 



50 75 33 ... 22-1 



75 100 ... 12 ... 8-1 



Over 100 8 ... 5-0 



149 100-0 



The loch was surveyed on June tf, 1903, when the elevation was found 

 to be 420-0 feet above the sea; when visited by the Ordnance Survey 

 officers on August 31, 1804, the elevation was 422'9 feet above sea-level. 



Temperature Observations. Serial temperatures were taken in the 

 deepest part of the loch with the following results : 



Surface 60O Fahr. 



10 feet 59-8 



20 55-7 



45 , 47-8 



90 47-0 



These observations show a range of 13 from surface to bottom, there 

 being a fall of about 4 between 10 and 20 feet, and a further fall of about 

 8~ between 20 and 45 feet. 



Loch Dubh-mbr (see Plate XXXI.). Loch Dubh-mor is a small but 

 comparatively very deep loch situated less than a mile to the south-east 

 of Loch Tralaig, and little more than a mile to the north-west of Loch 

 Avich. The outline is sub-circular, though the shore-line is somewhat 

 irregular, the maximum diameter being about one- third of a mile. The 

 superficial area is about 30 acres, of which 54 per cent, is covered by less 

 than 50 feet of water, and 9 per cent, by more than 100 feet of water. 

 Near the north-eastern shore is a small deep area enclosing the maximum 

 depth of 114 feet, the shore-slope being steepest in this locality. The 

 volume of water is estimated at 66 million cubic feet, and the mean depth 

 at 51 feet. The elevation could not be determined by levelling, but is 

 apparently about 900 feet above the sea. 



Temperature Observations. Serial temperatures taken on June 5, 1903, 

 in the deepest part of the loch gave the following results : 



Surface 57-4 Fahr. 



10 feet 57-0 



15 , 54-6 



20 49-2 



25 47-8 



50 , 46-0 



100 .' 44-7 



These readings are all lower than those taken at sim lar depths in 

 the larger Loch Tralaig on the following day, the difference at the depth 

 of 20 feet, for instance, being as much as 6 7 '5- The range shown by 

 these observations is 12 - 7, the most rapid fall being recorded between 



