THE FRESH-WATER LOCHS OF SCOTLAND. 



15 



feet, and the mean depth at nearly 21 feet, or 50 per cent, of the 

 maximum depth. The length of the loch is 28 times the maximum 

 depth, and 56 times the mean depth. 



Lochan Dubh is very simple in construction, shoaling on all sides 

 down to the deepest part. As in Loch Chon the slope seems to be much 

 steeper off the western than the eastern shore, a cast of 35 feet having 

 been taken comparatively very close to the west side. The water 

 shallows where the loch narrows a little above the outlet, a depth of 

 3i feet being found where the bottom is covered with reeds. The area 

 of the bottom between the shore and the 25-feet contour line is about 

 7 acres, or 60 per cent, of the area of the loch, and that deeper than 

 25 feet is nearly 5 acres, or 40 per cent. 



FIG. 10. LOCH ARD, WITH BEN LOMOND IN THE DISTANCE. 



(Photograph by J. Valentine.) 



Loch Ard (see Plate IX.). Loch Ard receives the outflow from 

 Lochan Dubh and Loch Chon ; it trends in an east and west direction, 

 sending out one prolongation to the south and another to the east. Its 

 level is 105 feet above the sea. It is over three miles in extreme length, 

 including the eastern prolongation, but the body of what may be called 

 the loch proper is about 2 J miles in length : from the head of the loch 

 to Helen's rock. The greatest width, measured from the extremity of 

 the southern prolongation to the northern shore of the loch, is over one 

 mile, the mean breadth being two-fifths of a mile. Its waters cover an 

 area of over 600 acres (nearly one square mile), and it drains an area of 

 more than ten times greater, or about 6250 acres (9J square miles). The 



