LAKE MAGGIOKE 373 



north end it merges with the delta of two torrents which enter the lake 

 in parallel beds at Intra. Going up the delta from Intra, on the road 

 between the two streams, the ascent steepens more and more rapidly 

 until near the hamlet of Torbasso, 2 miles back, the deposit becomes 

 a mass of cobbles and small boulders, over 150 feet above the lake. 

 The north stream is the San Giovanni, and the south stream, which 

 is much the larger of the two, is the San Bernardino. From its hor- 

 izontal extent this delta evidently does not represent a deep filling. 

 My aneroid readings make the level plain south of the San Bernar- 

 dino about 50 feet above the lake and the same for a similar area in the 

 north part of Intra. The flatness of the plain, the fineness of its soil, 

 and the apparent relation of the plain to the San Bernardino cone 

 suggest that at least the surface or top dressing of the plain is the work 

 of distributaries from the San Bernardino carrying only fine sediments. 

 One mile northeast of Intra there is a small but very prettily formed tor- 

 rent delta, and its edge at the front of the terrace stands at about the 

 same height as the flat in the village. 



The next deposit examined was at Luvino, on the east shore. At this 

 place delta deposits are beautifully developed in terraces at two levels, 

 but the situation and the history of these deltas are quite different from 

 those of typical torrents. The deltas at Luvino are not torrent deltas, 

 but are deposits of what one may call a less strenuous stream, the Tresa, 

 which carries the overflow of lake Lugano. The Tresa descends about 

 250 feet in 7 or 8 miles, but nearly all of its fall is in its lower half. It 

 receives no tributary torrents, except three or four very small ones in its 

 upper half. The head of the main or upper delta is at the upper mill 

 at Creva, a small village at the falls of the Tresa, about one and a half 

 miles southeast of Luvino. The head of this delta is about 100 feet 

 above lake Maggiore and its front, rather illy defined, about 80 feet. It 

 is composed of a rather fine grade of gravel, and largely also of sand) 

 and is thus stronglv contrasted with the verv coarse materials of the 

 torrent deltas. 



Below the main terrace, about 45 feet above the lake, is another 

 smaller, less conspicuous bench. Considering the character of the Tresa 

 and its relatively scanty sources of detrital supply, it seems probable 

 that the heavy upper terrace at Creva is associated with a glacial river 

 of larger volume than the present Tresa and acting when the glacier 

 was still present in the northern half of the Maggiore basin. The lower 

 terrace was probably built by the Tresa at normal volume mainly out of 

 materials excavated from the upper deposit. 



Three miles north on the east shore is Maccagno. Here is a torrent 

 delta in typical development. The torrent issues now through a narrow 

 ravine cut in the south part of the old delta. The main part of the vil- 



