546 Prof. T. G. Bonney—Alpine Passes and Peaks. 
This range has been cut away, as the great glen of Macugnaga was 
being deepened and enlarged, devouring the mountain group by 
which it is fed. 
I pass on to another peculiarity, which admits of a similar ex- 
planation. Not unfrequently the higher peaks, especially in the 
district south of the Little St. Bernard, project slightly from the 
watershed on to the Italian side, like bastions from a wall. Such is 
the case with the Ciamarella, the Roche Melon, the Viso, and others. 
The Viso, indeed, is wholly an Italian mountain, for it is the culmin- 
ating point of a long and deeply gashed spur, extending towards the 
south-east from the main range of the Alps. The course, indeed, of 
the line of watershed is suggestive, for it forms about the head of 
the river Guil (flowing westward) a kind of cusp, near the point of 
which is the Viso. On the northern side of this cusp rise the tribu- 
taries of the upper waters of the Po; on the other, the feeders of a 
hardly less important Italian stream, the Vraita. To understand the 
orographical structure, I look back to a stage in the process of 
mountain sculpture when the line of watershed passed over the 
summit of the Viso, and its crest, elevated to perhaps a couple of 
thousand feet above the present level, ran in the same general direc- 
tions as it now does, but some distance on the Italian side. The 
Guil continued to cut its way back towards the main peak, though 
slowly, as the slope of the upper part of the valley is not rapid. 
The glens of the Vraita on the one side of the peak and of the Po 
on the other side worked their way back more rapidly, and devoured 
the actual crest of the range. The descent on the Italian side is 
much more rapid than on the French; from the gaps, by which the 
range can be crossed from the latter country, to Crissolo in the Val 
di Po, is a drop of nearly 5000 feet. The descent from the Col de 
Vallante to Chateau Dauphin in the Val Vraita is about as much, 
while on the French side it would require some miles more walking 
to reach this level. Thus the Viso has been left projecting as a 
bastion. But nearly simultaneously with the above recession, two 
ravines, one tributary to the Po, the other to the Vraita, were cutting 
back into the curtain wall which connected the bastion peak of the 
Viso wall with the retreating crest of the watershed, until at last 
the heads of these glens met, and formed a kind of high-level ditch 
which isolates the peak from the actual watershed. 
A similar principle may be applied to explain a very common 
feature in the higher regions of the Alps—namely, that the culmin- 
ating peaks of important spurs are often hardly less elevated than 
those on the watershed. As an example, let us return to the 
Pennine range in the neighbourhood of Zermatt. The two branches 
of the Visp are divided and are bounded respectively by lofty ridges. 
A line drawn along the crest of the westernmost ridge would pass 
across the gap occupied by the Zmutt glacier to the peak of the 
Matterhorn; that drawn along the central ridge, as already said, 
would pass above the vast cirque at the head of the Val Anzasca to 
the Monte delle Loccie, east of Monte Rosa, while that along the 
easternmost ridge ceases rather abruptly near the head of the Val 
