of Edinburgh, Session 1871 - 72 . 
547 
Observations on the Fresh Waters of Scotland. 
Looking around me for some general theme suitable for the sub- 
ject of this introductory address, I became oppressed with the 
persuasion, that no such subject, worthy of j^our acceptance, had 
been left unexhausted by the able men who have lately had to treat 
of scientific topics of a general nature in circumstances akin to my 
own on the present occasion. I therefore thought I might trust to 
your indulgence, ^and substitute for a general address a notice of 
some inquiries, which have been carried on from time to time dur- 
ing my late occasional autumn holidays, and which promise results 
of some interest, illustrating the hydrography of the fresh waters 
of Scotland. These inquiries have in several respects been pushed 
not so far as to satisfy me completely. But as I may not be able 
to carry them through according to my present design, and I hope 
that others may be led to interest themselves in also pursuing them, 
I beg to submit the results to the Society, such as they are. 
The topics I propose now to bring forward, — which are rather 
diverse in nature, yet not altogether unconnected with one another, 
—are three in number, — First , The composition of the water of 
certain lakes and their leading streams in Scotland, and the changes 
their waters undergo in the streams which the lakes feed ; Secondly , 
The temperature of these lakes at various depths ; and, Thirdly , 
The action of their waters upon lead. 
I shall commence by recalling shortly the geological structure of 
our country, by which in a great measure the nature of its waters 
is regulated. 
In the 7 primitive formations which constitute the 11 Scottish 
Highlands” of ordinary speech, — for in correct language many 
parts of the so-called “ Lowlands ” are as well entitled to the other 
name, — we find that the mountain summits are either pointed or 
rounded, but seldom table-topped ; that their spurs are commonly 
rather sharply ridged; that their surface abounds in precipices, 
crags, loose blocks, rocks, and stones ; and that the valleys between 
them, except in the course of our largest rivers, are narrow, gravelly, 
or rocky, thinly covered with vegetative soil, and consequently 
little fit for plough cultivation. Not infrequently, however, the 
spurs or buttresses, instead of being ridgy, are broad and flat, 
