20 
Proceedings of the Royal Society of Edinburgh. [Sess. 
The distribution shown in the figure must be another consequence. It 
shows that there is a much greater quantity of water between 43° and 44° 
than usual, and compared with figs. 8 to 13 it shows that the water below 
43° is very much less than usual. There has, then, been a great mixing of 
the water formerly below 43° with the water above that temperature, which 
can be satisfactorily explained on the assumption that there is a secondary 
return current which gradually carries water from just below the discon- 
tinuity layer to greater depths, thus raising the temperature of water at 
these depths. It is found that, during the autumn or third phase of the 
temperature cycle, the lowest layers gradually rise in temperature. The 
example given is an extreme case, and we find that, whereas before the storm 
of the 25th to the 28th the temperature at a depth of 700 feet was 42 T°, 
observations taken thereafter show that the temperature at these depths 
was about half a degree higher, and all the water of lower temperature 
than about 42’5 0 had disappeared. On 29tli August, just after the wind had 
fallen, a series of observations was taken for 7 miles up the loch, with the 
result shown in fig. 4. It shows at a depth of over 300 feet a great body 
of water at a temperature between 45° and 46°. It will be remembered 
that on the previous day the surface temperature, on account of the return 
current, was only 46*2°, as the discontinuity layer was just above this 
temperature. This body of water must then, I think, be the accumulation 
of water caused by the primary return current ; and, as mentioned on page 9, 
there may be illustrated here the temperature bore which the experiments 
lead one to expect. At all events, the observations taken two days later, on 
the 31st, show practically no trace of this body of water of a temperature 
between 45° and 46°, and it is contrary to all other evidence to say 
that this body of water has in so short a time become mixed up with the 
surrounding water. It may be that the distribution shown in fig. 14 is 
caused by the return of the temperature bore at a greater depth. The rate 
at which the bore would travel is quite agreeable to this explanation. 
However that may be, the observations are, I think, sufficient to warrant an 
assertion that surface winds induce movements at the bottom of even our 
deepest lochs. 
( Issued separately December 24 , 1907 .) 
