122 THE FEESH- WATER LOCHS OF SCOTLAND 
in Loch Ness, however, made after gales, show considerable distortion 
of the isotherms at the bottom of the lake, which can only be 
explained by the existence of currents reaching to the bottom. 
The observations on 31st August 1903 may be taken for the sake of 
example. They are shown in fig. 46, which is constructed in the 
same way as fig. 47, on a diagram representing the south-west half 
of the lake. For temperatures below 44"" Fahr. the isothermals are 
■ 
Fig. 46. 
drawn for each tenth of a degree ; above 44° they are drawn for 
each degree. 
A typical distribution of the isotherms in a lake during autumn 
is shown in fig. 47. They are bunched together at the end of the 
lake towards which the wind is blowing, and radiate like a fan 
towards the opposite end. This distribution can be easily explained 
on the assumption that the current system is as has been described. 
The first effect of the wind is the accumulation of a large quantity 
of warm water at the lee end of the lake, and in consequence the 
upper isotherms slope downwards from the windward end. The 
