1907-8.] The Temperature Changes in Fresh-Water Lochs. 15 
slower than the ordinary return current by which it is induced. From the 
photographs of the experiments shown in fig. 5 , it is seen that in the 
Fig. 8. — Loch Ness, 6 a.m., 13th September 1904. 
experimental trough this secondary return current is felt right to the 
bottom of the trough, and my opinion is that in deep lochs also the second- 
