THE FRESH- WATER LOCHS OF SCOTLAND. 375 



which extends 5 miles west from the loch, among peaks rising to 

 nearly 2500 feet. Two branch glens extend several* miles to the 

 north, and one of these brings the overflow of a small loch, Lochan 

 na Beinue Baine, which was not surveyed. As a consequence of the 

 extensive drainage area, the loch is subject to great alterations of level. 

 The river has laid down long spits of sand, and threatens to silt up 

 the loch altogether. A very short stream conveys the overflow to the 

 sea; there is a boss of rock on the north side where it leaves the loch. 

 In volume Loch nan Gabhar is the last in the basin, containing only 

 5 millions of cubic feet, or one million less than the volume of an Dubh 

 Lochan. 



The temperature of the water on May 12, 1903, was 51'5 Fahr. at 

 the surface and at the depth of 5 feet. 



The particulars regarding the lochs in the Lochy basin are collected 

 together in the table on p. 374 for convenience of reference and com- 

 parison. From this table it will be seen that in the twelve lochs under 

 consideration, which cover an area of about 20 square miles, nearly 

 2600 soundings were taken, or an average of 214 soundings per loch, 

 and an average of 129 soundings per square mile of surface. The 

 aggregate volume of water contained in the lochs is estimated at 85,855 

 millions of cubic feet, or more than one-half of a cubic mile, and the 

 area draining into them is over 270 square miles, or nearly fourteen 

 times the area of the lochs. 



The Red Indian at Tullocli. The Red Lochaii, called in Gaelic by 

 a name which signifies " brown eye," is a very small pond lying in an 

 extensive morainic terrace at Fersit, near the north end of Loch Treig. 

 It is only about 30 yards in its longest diameter, and 5 feet deep in 

 the centre, is fed only by rains, and has no outflow except by percolation 

 through the gravel, yet its surface is maintained almost constantly at 

 the same level. The water is always turbid, and varies in colour from 

 dull green to brown or red. 



It was first examined by Sir John Murray in May, 1902. The water 

 was then brown; the collection taken with the coarse net very pale 

 yellow ; that taken with the fine net a decided red. At that time there 

 were only two very abundant organisms the larva of an insect, 

 Corethra, known as the "phantom larva," and a reddish-coloured rotifer, 

 Anurcea valga. There were niany other rotifera, entomostraca, and 

 other organisms common in ponds, but none of these were abundant 

 enough to be held responsible for the colour of the water. The 

 collection made with the fine net was examined by Dr. T. N. Johnston 

 and Mr. James Murray. On adding a little formalin, which killed the 

 animals, a blood-red sediment was deposited, which was found to 

 consist chiefly of A. valga and myriads of its red eggs. At that time 

 this species seemed to be mainly the cause of the red colour. 



