16 Professor T. G. Bonney — Lake-basins in the Alps. 



seven and eight hundred yards. It is almost enclosed by steep 

 slopes and crags, and is entered through a narrow V-shaped gully, 

 with a rapidly rising ridge on either side. Through this gully runs 

 the stream which carries off the water of the lake. I followed 

 a track which mounts gradually up the right bank, and no blocked 

 outlet exists on that side ; I had an excellent view of the other bank, 

 and feel certain there could not be one there. In fact, the rapid 

 rise of the rocky ridge on either side and its outline are almost 

 conclusive to an eye accustomed to mountain forms against there 



South. 



North. 

 Fig. 1. — Broken horizontal lines : Gneiss. 



Vertical lines : Schists, micaceous, etc. 



White: Water. 



(Scale as belo-w, Fig. 2, on p. 17.) 



being any outlet to the cirque but the present one. At this the live 

 rock can be seen not only on either side but also in the bed of the 

 stream. Of that I could be sure, because the channel had been 

 deepened, appai-ently in order to add slightly to the pasture-land by 

 lowering the level of the lake, and had been cut down for about 

 four feet into the solid rock. Above the cliffs is an undulating tract 

 of pasture, forming a kind of step, on which is a small shallow 

 tarn, and from this rocky slopes lead to the crest of the range, the 

 lowest part of which, at the Passo Campolungo, is 7,595 feet above 

 the sea. Thus the Lago Tremorgio is enclosed between two lofty 

 spurs from the range, somewhat in the position of the seat of an 

 armchair. 



The next rock-basin, the Lago Eitom ^ in the Val Piora, is on the 

 opposite side of the Yal Bedretto, at almost exactly the same 

 elevation above sea-level.^ Its position is remarkable. A mass of 

 crystalline schists, calcareous, quartzose, and micaceous, with some 

 overlying rauchwacke, are apparently infolded between two masses 

 of gneiss, of which the southern forms a high spur separating the 

 Val Piora from the Val Bedretto, and the northern belongs to the 

 watershed of the Lepontine Alps. Thus the Val Piora occupies 

 a kind of trough between these two masses of gneiss, which runs 



^ I was there for some time last summer, and had already paid four short visits. 

 2 It is a few inches over 6,000 feet. 



