402 Proceedings of Royal Society of Edinburgh. [sess. 
under the direction of Dr Gemmill, was sent into the Caledonian 
Canal, and many hauls were taken with the dredge and trawl, as 
well as with different kinds of tow-nets, in Lochs Lochy, Oich, 
and Ness, down to the greatest depths (500 and 750 feet). 
Before entering on the subject of this paper, I beg to tender to 
Sir John Murray my most cordial thanks for his invitation and 
for his kindness to me during my stay in Scotland. As regards 
limnological explorations, Scotland was a few years ago a complete 
terra incognita , hut when the work of the Lake Survey is com- 
pleted there will undoubtedly be no other country in which the 
lakes have been better studied than in Scotland. On Loch Ness 
I learnt the methods employed in taking the temperature and 
other physical observations ; and when the numerous observations 
and enormous mass of material have been worked out, I think that 
Loch Ness, as regards the bathymetrical and other physical con- 
ditions, will be one of the best explored lakes in the world — 
perhaps only equalled by the Lake of Geneva. 
It has hitherto been difficult to give equal prominence to the 
physico-chemical investigations, on the one hand, and the biological 
investigations, on the other, in the study of the lakes in different 
countries, owing mainly to the lack of scientists versed in the 
different branches of limnology, and interested alike in these two 
great departments. The admirable explorations carried on by 
Professor F. A. Forel and his pupils show what excellent results 
may be obtained when the investigations are planned on a uniform 
basis. I trust that Sir John Murray and Mr Laurence Pullar will 
agree with me in expressing the hope that, on the completion of 
the bathymetrical and physical survey so admirably commenced 
by Sir John Murray, and continued at the joint expense of both 
gentlemen, the work may he still further carried on in such a 
manner as to utilise the results yielded as to the biological 
study of lakes. I am quite well aware, as will be seen from 
the following pages, that the study of organisms, and especially 
of the influence of organic life upon the general conditions of a 
lake and its environs, presents greater difficulties in alpine 
countries than in lowland countries. The problems presented 
by the local conditions of lakes can perhaps be better studied 
in Scotland than in any other country ; and I sincerely hope that 
