184 PKOF. E. J. GARWOOD ON THE [May I906, 



level of the lake sinks several metres below its outlet in winter, 

 and the other is the occurrence of springs (issuing from the precipice 

 below the lake) which continue to flow all the year round. This 

 latter circumstance has been made use of by the engineers of the 

 St. Gotthard Railway, who obtain the water for their locomotives, 

 not from the overflow-torrent from the lake, but from these 

 permanent springs. The solution of the calcareous portions of the 

 schist might cause the funnel-shaped hollow in which the lake 

 lies : but it is also possible that the dolomite which occupies the 

 Campolungo Alp may have been folded in under the lake, as shown 

 in the very suggestive section to the west of the Campolungo Pass 

 (see PI. XIII, fig. 2). If this fold be continued underground, it 

 must certainly pass beneath the lake. The fact that the outcrop 

 of the dolomite strikes across the schist, and terminates abruptly at 

 either end against the gneiss, only to reappear as an isolated outcrop 

 in the Val Piumogno on the east, is a very suggestive one, as it 

 emphasizes once more the inconstancy of these eyes of dolomite and 

 their fortuitous occurrence among the crystalline rocks. 



Of the remaining lakes of this group, those scattered along the 

 southern side of the Ticino watershed are the most important. 

 They drain either directly into the Val Maggia, or indirectly 

 through the Yal Bavona. The Lago di Naret has a wedge of 

 crystalline limestone running across it, while the Lago Sciundrau 

 is situated on the junction of dolomite and gneiss. The Laghetti 

 or lakelets to the east of Lago di Naret, again, lie along the 

 junction of the calcareous schist and the gneiss ; their origin would 

 appear, therefore, to be similar to that of the lakes of the Yal 

 Piora. But, without soundings and detailed investigation, it is 

 best to leave their origin an open question for the present, as they 

 will well repay further investigation. 



IY. The St. Gotthard Lakes. (For topographical 

 map, see p. 186.) 



At the northern end of the Canton lie a small group of lakes 

 near the summit of the St. Gotthard Pass. Of these, the Lago della 

 Sella and the Hospice-tarns drain southwards by the Yal Tremola 

 to the Ticino, while the Lago di Lucendro, the Lago Orsirora, and 

 the Lago Orsino supply the headwaters of the infant Eeuss. 



The Hospice-lakes are small rock-pools, which owe their existence 

 partly to artificial means, having been in some cases dammed by 

 the old monks of the Hospice to serve as fishponds, which still 

 yield fine trout. They are also partly due to the highroad em- 

 bankment thrown across the swampy summit of the pass. The 

 portion of the largest lake north of the road is only about 16 feet 

 deep ; the southern portion appears to be deeper, but I should 

 think cannot exceed 50 feet in depth. 1 Of the others, the Lago 

 di Lucendro is by far the most important. 



1 The deepest sounding met with. 



