There is something mysterious in loch-fishing, in the tastes and habits of the fish which inhabit the innumerable lakes and tarns of Scotland. It is not always easy to account either for their presence or their absence, for their numbers or scarcity, their eagerness to take or their "dourness." For example, there is Loch Borlan, close to the well-known little inn of Alt-na-geal-gach in Sutherland.