Vol. 62.] TAKNS OF THE CANTON TICINO. 183 



in front till they nearly meet, so that it could only be sat in with 

 the legs crossed. It is obvious that, in considering the origin of the 

 lake, we must take into account the whole of this funnel before it 

 was breached at the exit, as it is probable that the water of the 

 lake once stood at a much higher level before the notch had been 

 eroded and cut down to its present depth. 



The basin does not lie in the path of any valley, for, with the 

 exception of a small stream coming down a gully from Pone. 

 Tremorgio on the west, the only drainage that it receives pours over 

 the southern rim of the funnel from the Campolungo Alp. 



This stream originates in a small lake, apparently a rock-basin, 

 lying high up at 7436 feet above the sea, north of the Campolungo 

 peak. Local tradition has it that this lake is unfathomable, 

 which probably means that it is more than 20 feet deep. The 

 stream from this lake appears originally to have flowed over the 

 Campolungo Pass westwards into the Val Maggia, and to have 

 been afterwards diverted into the Lago-Tremorgio drainage, 

 as the valley was carved out of the dolomite in which the 

 Campolungo Alp lies. The lake cannot, therefore, by any possi- 

 bility be regarded as occupying an overdeepened pre-Glacial valley, 

 and it resembles nothing so much as a large swallow-hole. 



The greatest depth of the lake is said to be 120 metres (394 feet) 

 near the centre. I give this on the authority of Mr. Fraser, an 

 engineer residing at Lugano, who took soundings from a raft. 

 Unfortunately, my attempts to sound this lake were frustrated on 

 two occasions ; the first time by bad weather and fogs, and the 

 second time, after partly completing the soundings, the line was 

 so repeatedly cut by sharp submerged reefs that I was obliged to 

 abandon the endeavour, the time at my disposal preventing a third 

 attempt. The discovery of these reefs, however, is not without 

 bearing on the origin of the lake. From the soundings which I 

 obtained, the depth appears to increase very regularly from the 

 western corner towards the centre ; and if this general slope con- 

 tinues, it would give a depth of 250 feet at the centre of the lake. 

 This is not the case, however, near the northern shore, which falls 

 steeply from the outlet. The lake is excavated in the calcareous 

 schists. The reefs running out from the south-western corner 

 contain ' eyes ' of massive andalusite with a hardness of 7|. 



The lime in the calcareous schist is chiefly present in the form 

 of eyes of crystalline calcite, which measure frequently several 

 inches across, and crumble at the touch ; and, where portions of 

 the rock were obtained from the edge of the lake, these eyes w 7 ere 

 frequently represented by holes, the calcite having been entirely or 

 partly dissolved out. 



The lake cannot be considered as the result of glacial erosion. 

 The production of a funnel-shaped hollow 1000 feet deep, with an 

 upward slope of 30° on the exit-side, cannot have been produced by 

 ice-action ; and the origin of the hollow in which the lake lies 

 must, I think, be attributed to chemical solution. Two important 

 facts seem to bear on this hypothesis ; one is the way in which the 



