THE FRESH-WATER LOCHS OF SCOTLAND. 35 



Feet. Acres. Per cent. 



Oto25 32 ... 39 



25 50 40 ... 48 



Over 50 11 ... 13 



83 100 



Temperature Observations. A reading at the surface at the north end of 

 the loch, on commencing the survey on September 11, 1902, gave 58*6 

 Fahr., while a series taken at 3.30 p.m., in the deepest part of the loch, gave 

 the following results : 



Surface 57-2 Fahr. 



10 feet 57'0 



25 56-0 



50 55-5 



These observations indicate a total range of temperature throughout the 

 body of water amounting to 3'l, no very decided fall being observed 

 beneath the surface, but the difference of nearly 1| between the two 

 readings at the surface is noteworthy. 



Loch Duartmore (see Plate XIII.). Loch Duartmore is a small, irregular 

 loch, trending almost east and west, and over a quarter of a mile in length. 

 Its waters cover an area of about 13 acres, while, since it receives the 

 overflow from Lochs Allt na h-Airbhe and Eucail, its drainage area is very 

 large about llj square miles, or more than 550 times greater than the 

 area of the loch. The maximum depth of 22 feet was observed near the 

 east end of the loch. The volume of water is estimated at 3 million cubic 

 feet, and the mean depth at nearly 6 feet. The loch was surveyed on 

 September 1J, 1902, when the elevation of the lake-surface was found 

 to be 81*5 feet above the sea ; this was -i feet lower than the level of Loch 

 Eucail, and 38 feet lower than that of Loch Allt na h-Airbhe. 



Loch Duartmore is on the whole very shallow, the area of the lake- 

 floor covered by less than 10 feet of water being about 12 acres, or 92 per 

 cent, of the total area. Only in two places were depths extending 10 feet 

 recorded : (1) at the extreme eastern end, where soundings in 10 to 22 feet 

 were taken, and (2) off the northern shore, near the middle of the loch, 

 where soundings in 12 and 16 feet were taken, the last-mentioned only 

 about 20 feet from the shore, indicating a steep slope in this position. 

 Some of the bays are filled with reeds. Temperatures taken in the deep 

 part at the east end, at 2 p.m. on the date of the survey, gave 55*0 Fahr. 

 at the surface and 54-6 at a depth of 17 feet. 



In the ten lochs included in the following table 994 soundings were 

 taken ; the aggregate area of water surface is 3'35 square miles, so that 

 the average number of soundings per square mile of surface is 296. 

 The aggregate volume of water contained in the lochs is estimated at 6679 

 millions of cubic feet. The area drained by these lochs is over 59 square 

 miles, or nearly 18 times the area of the lochs. 



