THE FRESH-WATER LOCHS OF SCOTLAND. 



251 



corresponding approximately with the level of the sea), and is flat- 

 bottomed in character, as shown in cross-section C-D on the map. 



The areas between the consecutive contour-lines drawn in at equal 

 intervals, and the percentages to the total area of the loch, are as 

 follows : 



to 25 feet 

 25,, 50 

 50,, 75 

 75,, 100 

 Over 100 , 



187 acres 



111 



88 



20 



18 



424 



per cent. 



26-0 



20-9 



4-8 



4-2 



100-0 



Temperature Observations. The temperature of the surface water 

 in Loch Eilt during the two days spent on it varied from 58 to 60 

 Fahr. On July 10, 1902, three series of temperatures were taken 

 beneath the surface, one in each of the three basins into which the loch 

 is divided, with the following results : 



Depth in feet. 



Loch Eilt (eastern 



basin). 



July 10, 1902, 

 2-30 p.m. 



Loch Eilt (central 



basin). 



July 10, 1902, 

 3'30 p.m. 



Loch Eilt (western 



basin). 



July 10, 1902, 

 5p.m. 



These series show a constant temperature down to 20 feet in each 

 case, but the water in the deep western basin was 2 warmer than in 

 the other two basins. Beyond the depth of 20 feet, again, the tem- 

 perature was about 2 higher in the western basin than in the central 

 basin, and 2 higher in the central basin than in the eastern basin, so 

 that at a depth of 100 feet in the western basin the temperature was 

 rather higher than at a depth of 50 feet in the eastern basin. The 

 water in the western basin was warmer at all depths than that in the 

 central basin, and in the central basin than in the eastern basin. To 

 explain this peculiar distribution of temperature in the waters of Loch 

 Eilt on the afternoon of July 10, 1902, the weather conditions during 

 the few preceding days must be taken into account. The wind had 

 been blowing strong from the north-east from the 3rd till the afternoon 

 of the 9th. Rain commenced to fall about 6 a.m. on the 9th, and 

 continued till about 8 a.m. on the 10th, so that during the twelve hours 

 from 9 p.m. on the 9th to 9 a.m. on the 10th the surface of the loch rose 



