THE FRESH- WATER LOCHS OF SCOTLAND. 241 



Burga Water (see Plate CI.) lies about 3 miles south-east of Sandness. 

 It is shaped roughly like the letter T, the stein of the letter running 

 nearly north -westto south-east, the cross-stroke at right angles to it 

 at the south end. There are low hills to the north-east, and higher 

 hills south-westward. Burga Water is one of an extensive chain of 

 lochs, forming one of the largest lake-systems in Shetland, of which, 

 however, only two lochs could be surveyed. Its length is fully half a 

 mile, and the greatest width, across the cross-piece of the T, is very little 

 less, viz. five-twelfths of a mile. The contours of the bottom are some- 

 what irregular, the 10-feet contour only nearly following the shore line. 

 The 2-feet contour zigzags from side to side of the loch, unless we 

 regard the various soundings on which it depends as isolated. Near the 

 south end is the maximum depth of 31 feet. 



The superficial area is 78 acres, the mean depth nearly 13 feet, and the 

 contents 42 millions of cubic feet. The chief sources of the loch are the 

 Burn of Cattikismires from the west, and the burn from Mousavord Loch 

 (not surveyed). Gibbie Laws burn flows from the east corner, lj miles 

 south-eastward into Voxterby Loch. The area draining into the loch 

 slightly exceeds 2 square miles. The islands at the south end are all of 

 rock ; there is rock exposed on the promontory on the west shore, and the 

 channel leading to the little loch on the east is choked by rock and stones, 

 so that it could not be entered. 



On the date of the survey, July 21, 1903, the surface was 115-65 feet 

 above sea-level, the water being low at the time, and liable to rise 3 feet 

 higher, On August 27, 1877, the Ordnance Survey officers found the 

 elevation to be 116'8 feet above the sea. The range of temperature was 

 2-4 Fahr.: 



Surface 56-8 Fahr. 



5 feet 56-l 



10 54-8 



15 , 54-6 



25 , 54-4 



Loch of North-house (see Plate C.) is a loch of moderate size in 

 Aithsting, about a mile north of Aithsting church. Its general form 

 is peculiar. There is a main triangular body, with the apex to the 

 south, from which a narrow arm runs to the north-west. The two 

 portions are separated by a gravel bar, at the north end of which there is 

 rock. There is also a bar of rocks near the outflow. The narrow portion 

 west of the bar has a depth of 7 feet, and is almost flat-bottomed. In the 

 main loch the maximum depth of 13 feet is at the north end, close to the 

 gravel bar, and from there it gradually shoals to the south. The total 

 length is five-sixths of a mile, the greatest breadth one-fifth of a mile. 

 The mean depth is 6J feet, the area about 58 acres, and the volume 16 

 millions of cubic feet. The drainage area measures about half a square 



B 



