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 llth, 12th, and 22nd 

 June, 1900, and again on the 1st September and the 23rd October. A 

 reading at the surface on the llth June at 5 p.m. gave 58 0> 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 June 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 llth 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 temperature 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. 



f " La quantite* totale de chaleur emmagasine dans un lac variera d'autant moins que 

 ce volume sera plus grand par rapport a cette surface " (Les Lacsjranqais, p. 150). 



