THE FRESH- WATER LOCHS OF SCOTLAND. 225 



Loch of Harray (see Plate XC.). The Loch of Harray, the largest in 

 the islands, lies immediately to the north of the Loch of Stenness. The axis 

 runs nearly north and sonth. The southern portion is elongate, with undu- 

 lating shore-line ; the northern part bifurcates into two broad inlets, giving 

 the whole loch the approximate form of the letter Y. The surrounding 

 land is undulating and everywhere low. The east side is principally farm- 

 land there are extensive wet meadows (as at Kirk Ness) moorland, 

 and here and there low cliffs of gravel or rock. The Bridge of Brogar is 

 built on the rocky barrier separating the Loch of Harray from the Loch of 

 Stenness. The length, measured in a straight line, is 4f miles, and the 

 greatest breadth 1| miles. The mean breadth is three-quarters of a mile. 

 There are many islands, extensive shoals, and isolated stones. The bottom 

 is flat, and the mean depth is about 9 feet. The greatest depth, 14 feet, 

 occurs nearly in the narrowest part of the loch. The superficial area is 3| 

 square miles, and the volume of water 951 millions of cubic feet. 



The area of country draining into the loch is about 45 square miles. 

 The largest streams are the Burn of Hourston, draining several small 

 lochs, and entering the Loch of Harray at the north end, and the Burn of 

 Netherbrough, flowing in at the east side. The outflow at the Bridge of 

 Brogar is, in certain states of the tide, converted into an inflow. There 

 was always a current out or in during the survey, but there was never a 

 measurable difference of level. The surface was 3*6 feet above sea-level 

 on August 21, 1903. The temperature was 55'0 Fahr. both at the surface 

 and at a depth of 14 feet. 



Though there is a free ingress of water from the Loch of Stenness, and 

 the shores of that loch are overgrown by marine algaB close up to the 

 Bridge of Brogar, the brackish water entering the Loch of Harray appears 

 to be insufficient to have much effect on its biology. No sea -weeds were 

 seen on the east side of the Bridge, the water was fresh to the taste, and 

 the ordinary fresh-water plankton animals were present. 



Loch of Bosquoy (see Plate XC.). A small loch of rhomboid form 

 near the north-east corner of the Loch of Harray, into which it drains 

 by a short mill stream controlled by a sluice. It is surrounded by boggy 

 meadowland. There are many islets of reeds in the western part of the 

 loch. The length is two-thirds of a mile, and the breadth nearly one- 

 third of a mile. The greatest depth is 5 feet near the north shore and 

 east end. There is a considerable flat-bottomed area 4 feet deep. The 

 mean depth is 2J feet, the area about 65 acres, and the volume 7 millions 

 of cubic feet. There is a considerable drainage area (3J miles) chiefly on 

 the Hill of Milldoe (734 feet) on the east, from which the Corrigal burn 

 flows. Where it enters the loch the stream is known as the Burn of 

 Layaw. The level was estimated at 36 feet above sea-level. 



Loch of Sabiston (see Plate XCI.). This small loch in the Harray 

 basin, also known as the Loch of Housby, lies 1J miles north of the 



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