Prof. T. G. Bonney—Alpine Passes and Peaks. 546 
principle of the unequal rate of recession of the heads of valleys on 
opposite sides of a line of water-parting might readily be multiplied, 
but I will notice only one other, and that briefly. Many of you 
will remember the structure of the Pennine Alps at the head of the 
Gorner glacier. Between the pyramidal summit of the Matterhorn 
and the massif of the Breithorn there is the marked depression 
crossed by the Théodule Pass—a breach in the rocky wall which is 
some two or three thousand feet deep ; for the summits on either side 
are respectively 14,705 feet and 13,685 feet above the sea, while the 
crest of the chain at the Théodule Pass is barely 11,000 feet. 
From the Breithorn the rocky rampart continues practically un- 
broken, in a general easterly direction, as far as Monte Rosa, its 
peaks being well over 13,000 feet in height, and even the gaps 
between them only about 1000 feet less elevated. In fact, from the 
Breithorn to Monte Rosa the crest of the range is never less than 
12,700 feet above the sea. It culminates in the vast ridge of Monte 
Rosa, the highest peak of which is 15,217 feet above the sea, after 
which the watershed between Switzerland and Italy runs north, and 
we find another gap similar to that above mentioned, except that 
here a comparatively level snow-field is terminated by abrupt pre- 
cipices on the eastern side. Hvery one who has crossed by one of 
the Weissthor passes, or who has ascended the well-known snowy 
hump of the Cima de Jazzi, will remember the startling contrast 
between the long and gentle ascent over slopes of snow on the 
western flank, and the precipitous descent on the Italian side. 
Between Monte Rosa and the Strahlhorn (18,750 feet) there is a gap 
of about three miles wide, the flattened crest of which undulates a 
little on either side of 12,000 feet. Besides this, a line of peaks, 
only a little subordinate to that of which Monte Rosa forms a part, 
terminates abruptly with the Strahlhorn almost on the watershed, 
instead of being prolonged, as might have been anticipated, by a 
spur on the southern side. Of this apparent anomaly we have not 
far to go in order to find an explanation. The head of the Val 
Macugnaga, which is a huge corrie, has cut back into the massif of 
Monte Rosa, and is partly enclosed by its eastern spur, which runs 
towards the Pizzo Bianco. The drainage from this corrie, starting 
in a northerly direction, sweeps round towards the east, passing 
under the great wall of cliffs which, as already mentioned, descends 
from the edge of the snow-field feeding the Gorner and the Findelen 
glaciers, and from that at the head of the Schwarzenberg glacier east 
of the Strahlhorn. Hence I conceive that the Strahlhorn was once 
part of a great spur thrown off from a range which extended in a 
direction rather east of north from Monte Rosa, and was elevated 
perhaps a couple of thousand feet above the present edge of the 
Gorner snow-field. The Cima de Jazzi might be a remnant of 
another spur from this range, and it is a noteworthy fact that the 
Monte delle Loccie, a peak over 12,000 feet on the eastern spur of 
Monte Rosa, is almost exactly on the line of the Strahlhorn axis. 
1 Possibly the curious shelf or trough of the Saas Weissthor is really the half of 
an old pass between the Strahlhorn and a missing peak. 
DECADE III.—VOL. V.—NO. XII. 3d 
