260 THE FRESH-WATER LOCHS OF SCOTLAND 
such a pleasant illusion. The water, which is maintained at a depth 
of about 7 feet by the dams, is used for the engines that generate 
the electricity for the lighthouse and the compressed air for the fog- 
horn. No aquatic phanerogams or higher cryptogams exist either in 
the water or about the shores of the loch, but the water is coloured 
yellowish-green by the abundance of minute Myxophyceae, Bacteria, 
Infusoria, and Entomostraca, and by the waste water from the 
adjacent engine-house. The water is so discoloured that the bottom 
can only be seen at a depth of a few inches, and the engineer informed 
me that the discoloration is maintained throughout the year. It must 
not be imagined, however, that the cliffs about the loch are bare of 
vegetation, for besides grassy slopes and banks, the rocks and crannies 
are clothed with a variety of plants such as are common to the 
maritime cliffs of the adjacent mainland. An account of the terres- 
trial plants is given in the original publication. 
In conclusion, I desire to express my obligation to Sir John 
Murray and Mr Laurence Pullar for the assistance they have at all 
times freely given me, without which these pages could never have 
been written. I should like also to thank Mr James Chumley for 
his generous help, so freely given on many occasions. 
University College, 
Dundee. 
