1907-8.] The Temperature Changes in Fresh- Water Lochs. 19 
A series of temperatures was taken along the loch on 25th August, and 
at that date the temperature distribution was quite normal. But the strong 
wind rapidly lowered the surface temperature at Fort Augustus. On the 
26th the surface temperature was 55 3 °, on the 27th, 52'5°, and on the 28th 
it had fallen to 46'2°. On the 28th it was evident that there was a very 
strong return current rising to the surface close into the shore at Fort 
Augustus. Observations were made in 7 feet of water, and it was found 
Fig. 14. — Loch Ness, 31st August 1903. 
that the temperature at the surface was as low as 43 '9°, and that at the 
depth of 7 feet the temperature was 46 ’6°, or nearly 3 degrees warmer. 
There was no such inversion of temperature further out in 50 feet of water. 
This must, I think, have been due to the return current bringing with it 
cold water from a considerable depth. The discontinuity, as will be seen 
from the figure, was sharpest at the isotherms for 46° or 48°, and as the 
surface temperature was just about 46° it is probable that the return current 
was strongly felt at the point where the Fort Augustus observations were 
regularly taken, which is what one would expect during a heavy wind. 
