THE FRESH-WATER LOCHS OF SCOTLAND. 
233 
when dry, and when wet plastic and creamy, not unlike cocoa and milk 
of a pink brown colour. The material is made up of probably 90 per 
cent, of clayey matter with minute mineral particles less than 0'05 mm. 
in diameter, the remaining 10 per cent, consisting of mineral particles 
with a mean diameter of 0‘15 mm. Quartz is the principal mineral 
species, but small grains of pink microcline-felspar are very abundant, 
• and it is apparently to this mineral that the pink colour of the deposit 
is due; the microcline shows cross-hatching, and is much kaolinized. 
The washed mineral grains have a decided pink tinge, which is, how- 
ever, much more pronounced in the fine washings. Besides quartz and 
felspar, white and brown mica, hornblende, garnet, and magnetite were 
observed. There is little or no vegetable matter. 
The particulars regarding the lochs in this basin are collected 
together in the table on p. 232 for convenience of reference and com- 
parison. From this table it will be seen that in the fourteen lochs under 
consideration, which cover an area of nearly 15 square miles, nearly 
2500 soundings were taken, or an average of 167 soundings per square 
mile of surface. The aggregate volume of water contained in the lochs 
is estimated at 44,500 millions of cubic feet, and the area draining 
into them is 185J square miles, or 12| times the area of the lochs. 
Notes on the Geology of the Loch Maree District. 
By B. N. Peach, ll.d., f.r.s., and J. Horne, ll.d., f.r.s. With 
Geological Map (Plate LI.). Published by permission of the 
Director of the Geological Survey. 
The Loch Maree district presents features of special geological 
importance relating to the subdivisions of the Archaean rocks, to the 
topography of the old pre-Torridonian land surface, and to the series 
of terrestrial movements which affected ,the north-west Highlands in 
post-Cambrian time. Throughout the mountainous region, stretching 
north to Dundonnell forest and south to Achnashellach and Glen 
Shieldaig, excellent sections are to be found showing the geological 
structure of that region. 
The Archaean rocks on map), lying to the west of the great post- 
Cambrian displacements, occur mainly in the north-west of the area, 
where they form a broad tract of mountainous ground between Loch 
na Sheallag and Loch Maree, and westwards by Torrisdale to Gairloch. 
There is also an important development of them on both sides of Loch 
Torridon above Loch Shieldaig, and they likewise appear as inliers, 
surrounded by Torridon Sandstone, as, for instance, on the southern 
slope of Beinn Dearg north of Liathach. Within the territory affected 
