30 
BATHYMETRICAL SURVEY OF 
from 50°*2 to 52°-2 ; the extreme range shown by all the observations 
amounts to 13°. 
Loch Leven . — Loch Leven* was sounded on the 11th, 12th, and 22nd 
June, 1900, and again on the 1st September and the 23rd October. A 
reading at the surface on the 11th June at 5 p.m. gave 58°*7, and on 
the 12th June at 4.50 p.m. a temperature of 67°:5 was observed — a 
range of nearly 9° in one day. This reading of 67°*5 may be specially 
referred to as being, so far as we are aware, the highest temperature 
hitherto recorded in the waters of Scottish lochs, the next highest 
reading being one of 65° observed by Mr. Scott at the surface of Loch 
Oich in August, 1897. In September the surface temperature ranged 
only from 57° to 58°-5. We are doubtful as to the working of the 
thermometer made use of in the October visit, and the readings have 
therefore not been included in the table. 
The serials taken in J une indicate the rapidity with which the waters 
of a shallow lake like Loch Leven become heated up in summer. During 
the eleven days between June 11th and 22nd the whole body of water 
had acquired a higher temperature, amounting to about 4° in the upper 
layers down to 30 feet, to nearly 3° at 50 feet, and to half a degree at 
60 feet. But, while the body of water in a shallow lake absorbs heat 
more rapidly than that in a deep lake, it also loses heat more rapidly, 
and therefore the quantity of heat stored up in the waters of a deep 
lake may not be less than that stored up in the waters of a shallow lake, 
as Delebecquef seems to think. From a preliminary study of our tem- 
perature observations in the Scottish lochs we believe the reverse to be 
the case. For instance. Loch Katrine and Loch Leven are comparable 
as regards superficial area, but Loch Katrine is six times as deep as Loch 
Leven, and contains twelve times as much water ; if the temperature of 
the water in the two lochs were taken simultaneously before and after a 
definite interval in summer, it seems probable that, while the tempera- 
ture in Loch Leven might have been raised much higher than in Loch 
Katrine, the amount of heat stored up, as represented by the number of 
cubic feet raised 1°, would be found to be greater in Loch Katrine than 
in Loch Leven, and that the difference would bear some relation to the 
ratio between the bulk of water and the area of surface exposed to the 
rays of the sun. We shall endeavour to work this matter out in greater 
detail as our temperature observations accumulate, and we may return 
to the subject in a later paper. 
Biology. — Tow-net and other observations show that the nature and 
* We understand that the tempei-ature of the water of Loch Leven has been taken at the 
pier once a day (at 12 noon) during the five months of the fishing season for the past twenty- 
five years, but we have had no opportunity of examining the observations. 
t “ La quantity totale de chaleur emmagasinee dans un lac variera d’autant moins que 
ce volume sera plus grand par rapport a cette surface ” (Les Lacs Jrangais, p. 150). 
