170 PKOF. E. J. GARWOOD OX THE [^ av I9067 



be traced westwards under the calcareous rocks on the north side 

 of the 1930-metre hill. It represents therefore almost exactly the 

 former line of junction of this gneiss with the overlying rauchwacke, 

 now removed by denudation over the area occupied by Lake Eitom; 

 and the existence of the bays and headlands seems in some cases to 

 have been determined by folds or crumplings, which must once have 

 affected both sets of rocks, as will appear by an inspection of the 

 bathymetrical contours. Some of the bays, however, are due to 

 stream-erosion, as shown by the abruptly-truncated strike. 



The general shape of this lake-basin is indicated on the bathy- 

 metrical chart (PL XVI). The greatest depth met with was 163 feet, 

 in the centre of the lake. The greater part of the lake is over 

 100 feet deep ; while an area, about 330 yards in length and 

 150 feet or more in depth, occupies what must originally have been 

 the centre of the lake, if we allow for the portion at the upper end 

 which is now filled with delta-material. The floor of Lago Eitom 

 is thus seen to form a very symmetrical trough, the axis of greatest 

 depth running east and west, practically down the middle of the 

 lake. The contours near the southern side are influenced by the 

 subaqueous folds of the gneiss for some distance from the shore. 

 The contours along the northern bank bear no particular relation 

 to the subaerial escarpment, being chiefly influenced by landslips and 

 rock-falls from the steep cliffs above : were it not for the loose 

 material thus accumulated, the northern shore would undoubtedly 

 descend much more steeply than it now does. 



Lago Tom (see Pis. IX, X, XII, & XVII).— This lake lies at 

 an elevation of 6637 feet above the sea. It occupies a hollow 

 directly above, and to the north of, Lago Eitom. In shape it is a 

 rough oval. Its greatest length from north to south is exactly 550 

 yards, and its greatest width from east to west about 350 yards. 



Prof. Bonney remarks in a footnote (op. cit. p. 19) : 



' Its area is given as 1000 square metres, and it is said to be shallow. But I 

 should think it would not be less than some 20 feet deep, and might be more.' 



The greatest depth that I obtained was exactly 50 feet. The lake, 

 again to quote Prof. Bonney : 



' occupies a kind of cirque, and lies in the strike of the same rocks [as Lago 

 Cadagnoj.fortheenclosing crags consist of similar amphibolitic and granatiferous 

 gneiss, and at the lower end is rauchwacke, which can be traced from the 

 southern side of the basin of the Lago Cadagno across the intermediate spur.' 



The lake terminates at its southern end in a wall of rauchwacke, 

 about 16 feet high. A short gorge leads into the heart of the 

 rauchwacke, near the eastern end of this wall; and after heavy 

 rain, when the lake is high, I have seen the water flowing through 

 this channel and disappearing underground. It reappears as a 

 spring farther west, on the south side of the barrier of rauchwacke, 

 exactly at the junction of that rock with the underlying schist. 

 After a spell of fine weather the level of the lake falls so that the 



