588 THE FRESH-WATER LOCHS OF SCOTLAND 
line between Montenegro and Turkey. The principal affluent is the 
Montenegrin river Moratcha, which enters the lake at the north- 
western end. The lake is 25 miles long by 5 or 6 miles wide, and 
covers an area of 137 square miles. Close to the steep south- 
western margin are over a dozen deep holes, the maximum depth of 
144 feet being found in one of these situated near the village of 
Radus. The mean depth is 16 feet, and the volume of water 
contained in the lake is estimated at about 60,000 million cubic feet.^ 
Recently a portion of the stream of the Drin, which is formed by the 
junction of the Rlack Drin and the White Drin and flows out into 
the Adriatic not far south of the Rojana, has found its way into the 
Rojana channel ; the result has been a rise in the level of Lake 
Scutari and the inundation of the adjacent lowlands. 
Lake Ochrida (or Okhrida), which occupies one of the plateaus 
of Eastern Albania, lies at an elevation of 2253 feet above sea-level, 
and is the chief source of the Drin. It is about 18 miles in length, 
from 4 to 7 J miles in breadth, and covers an area of 105 square miles. 
The maximum depth is 942 feet, the mean depth 479 feet, and the 
volume of water is estimated at 1,391,000 million cubic feet.^ 
Eiver Po. The River Po and its tributaries drain the plain of Lombardy, a 
valley of subsidence at the base of the great arch of the Alps (see 
flg. 71). For ages the river has been occupied in filling up this 
great depression, and at Milan a boring was sunk 530 feet without 
reaching the bottom of the river deposits.^ Such an accumulation 
would have required a longer period of time had not the river been 
assisted in its work by the large masses of loose debris which lie at 
the lower end of each great valley opening on the plain of Lombardy, 
and from which stones, sand, and mud are washed down in time 
of flood, and scattered across the plains by the Po and its affluents. 
These masses represent the moraines shed from the ancient glaciers 
that filled the Alpine valleys to the brim in the glacial period and 
fed the waters of the Po. A remarkable phenomenon, that has led 
to much discussion, is that, while there are lakes in some of these 
valleys at the present day, in others there are none, and it is difficult 
to understand how eroded detritus could have been carried along the 
former type of valley and yet have left it, as in the case of that 
occupied by Lake Maggiore, 2000 feet below the level to which the 
plain beyond has been filled. Lyell* suggested that the valley of 
the Ticino, in which Maggiore lies, had been so elevated and depressed 
1 See Halbfass, op. cit., p. 206. " Ibid. 
Penck, cited by Lubbock, op. cit., j). 137, 
^ See Ramsay, " Sir Charles Lyell and the Glacial Theory of Lake Basins," 
Phil. Mag., vol. xxix. p. 285, 1865. 
