408 Proceedings of Royal Society of Edinburgh. [sess. 
country, for the most part built up of hard rocks. Nearly all 
the lakes belong to the Highlands, the highest mountain peaks 
attaining an elevation of more than 4000 feet above sea-level. It 
is unnecessary in this short paper to enter into the chemical 
composition of the rocks, but I think I am right in stating that, as 
compared with Denmark, lime generally plays a subordinate r61e 
in the chemical composition of the Scottish Highlands, and I am 
of opinion that the amount of lime washed out by rivers and 
carried into the lakes is nearly everywhere inconsiderable. The 
Scottish rivers, with their rapid currents, their sources high up in 
the mountains, their great eroding powers and waterfalls, are quite 
different from our little brooks. As far as I could gather from the 
members of the Lake Survey staff, there are no special seasons in 
which the rivers carry exceptional quantities of water into the 
lakes or into the sea. At different times of the year, though 
probably mostly in spring, the rivers after heavy rains become 
swollen, and after periods of drought they become low, but this 
rise and fall are not, to the same extent as in Denmark, restricted 
to certain seasons, and the suddenness with which the Scottish 
rivers come down in flood has no parallel with us. 
These differences are closely connected with the wide divergence 
in the geological structure and climatological conditions of the 
two countries — the one a low country, with moderate rainfall ; the 
other mountainous, with a heavy rainfall,* the hilltops shrouded in 
mists, and the hills themselves clothed with peat or peat-mosses, 
which suck up the water like a sponge and feed the rivers. 
While Denmark has few lakes, Scotland has very many ; and 
though generally of moderate size, many of them are much larger 
than the Danish lakes. The main difference is the great depth of 
the Scottish lakes, often exceeding 500 feet, and in one case (Loch 
Morar) exceeding 1000 feet, and they are nearly all long and 
narrow, none of the larger ones being circular, as is the case with 
many of the Danish lakes. Their narrow form facilitates the 
renewal of the water, and the sudden flooding of the rivers at 
nearly all seasons of the year causes rapid changes in the level of 
the lakes. With these phenomena we have hardly anything to 
* In the western Highlands the rainfall is five to seven times greater than 
in Denmark. 
