of Edinburgh, Session 1881-82. 
483 
circulating, it seems impossible that the same water can be one 
colour at one place, and a different colour at another, but we can 
easily see how the different colours and degrees of brilliancy can be 
produced by the colour and the amount of suspended matter at the 
different places, — where the water is mixed with whitish particles 
being bluish, and where mixed with yellow particles, appearing 
greener, — whilst its brilliancy is determined by the amount of sus- 
pended particles which may be present at the time in the water. 
In conclusion, a lake in the Cordilleras is referred to as combining 
all the conditions necessary for producing fine and brilliantly blue 
coloured water. The traveller in describing this lake says, “ Its 
waters were of the most extraordinarily brilliant blue I ever beheld.” 
From the description, this lake is in many respects like the Lake of 
Geneva. It is provided with an abundant supply of pure glacier 
water, free from discolouring impurities, but laden with abundance 
of white-reflecting particles, whose presence is evidenced by a “ white 
strip ” around the lake. 
2. The Surface Geology of Mid-Lochaber. 
By Professor Duns, D.D. 
(Abstract). 
An attempt is made in this paper, mainly from the point of view 
of the Society’s “ Boulder Committee,” to examine and classify the 
surface-deposits of a comparatively small compact area, which is 
bounded on the north and north-east by the river Spean, on the 
south and south-west by the river Nevis, on the west and north- 
west by the Lochy and the Caledonian Canal, and on the east and 
south-east by the Nevis range of Mountains. Reference is also 
made to the district between the Nevis and Loch Linnhe, including 
Auchintore and part of Glen Nevis. The body of the paper is 
limited to the statement of phenomena. It is felt, however, that 
the chief value of a record of facts is to lead to a definite knowledge 
of the forces which underlie them, and of the laws of which they are 
the expression. 
I. Peat. — The chief deposits occur in Corpach Moss, and on the 
low ground which stretches on both sides of the Kingussie road 
vol. xi. 3 q 
