﻿Vol. 64.] AND ANTIGORITE-SERPENTINES. 157 



rock. Bat the number of the boulders shows that there must be 

 other outcrops in the Val Devero ; and Dr. S. Traverse ^ states that 

 serpentine occurs, among other localities, on the Pizzo del Cervan- 

 done, where it is said to contain both unaltered olivine and asbestos. 



We had next to determine whether any quantity of serpentine 

 was received from the Val Bognanco and the Val di Vedro, the 

 streams from which, at their junction with the Tosa, are only 

 about three-quarters of a mile apart, and thus, as their fans are 

 practically continuous, a boulder brought down even by the former 

 might very well be reckoned as occurring in the Val Antigorio. 

 After returning to Dome d'Ossola, we examined the stony plain 

 deposited by the torrent from the Val Bognanco, the main channel 

 of which must, I think, have formerly flowed to the south of its 

 present position. Here water-worn fragments of serpentine were 

 abundant : the larger (some 15 or 18 inches in diameter) more 

 angular than the smaller, which were often flattened ellipsoids in 

 shape; and the rock varying in structure from fairly massive to rather 

 schistose. It was in fact indistinguishable from that so common 

 in the upper part of the Saas Valley. Besides these, we found a 

 few pebbles of a rock consisting of a fibrous green hornblende and 

 rather saussuritic felspar, bearing some resemblance to one variety 

 of the noted eiiphotide from the Allalin Glacier, and many of gneiss, 

 which, however, generally was not of the ' Antigorio ' type. 



From this we went on to an extensive pebble-bed on the right 

 bank of the Doveria torrent, and thus part of the fan from the Val 

 di Vedro. Here serpentine was almost rare, and I saw only one 

 pebble of the euphotide just mentioned, but the Antigorio gneiss 

 was much more abundant, other varieties also occurring. The 

 Swiss map shows two rather small outcrops of serpentine in the 

 Val Bognanco,^ and none in the Val di Vedro ; but I think that the 

 facts stated above justify the conclusion that this rock must occupy 

 a considerable area in the former, and may even have a few small 

 outcrops in the latter valley ; though we must not forget that the 

 Tosa, when in flood, might contribute some pebbles to the stony 

 plain which is usually the ' dumping-ground ' of the Doveria. 



After this we crossed the Tosa above Domo d'Ossola, where it is 

 divided into three or four channels, and examined the pebbles on an 

 island very near its grass-grown eastern bank. This, under ordinary 

 circumstances, must be out of range of the two above-named 

 streams, but some stones might have come from the Val Devero, or 

 have been brought by the tributary from the Val Vigezzo (which we 

 were unable to visit). Here pebbles of serpentine were not very 

 common, but of the usual types ; we also found some of a white or 

 greyish marble, occasionally micaceous, representing that already 

 mentioned ; a few of the hornblendic euphotide ; a fair amount 

 of the Antigorio gneiss with some other varieties, and sundry 



1 ' aeologia dell' Ossola ' 1895, pp. 169-71. 



■' Scale j5ji-^. In Dr. Traverse's map (scale ^^) there are at least four, 

 one being crossed by the torrent not far from the mouth of the valley. 



