_ON GLACIERS._
The _Alpine Journal_ for November 1868 concludes with these words, “If
anybody thinks that Alpine science has been already too thoroughly
drilled into the public mind, we would refer him to a recent ridiculous
letter which the editor of the _Times_ did not think it beneath him to
publish, and in which the writer said that a ‘puff of smoke,’ as it
appeared on the mountain, ‘raised the cry that the Glacier des Pélérins
had burst, carrying with it part of the moraine which kept it within
bounds!’”
If any one had told the climbing world in those days that in 1891 the
ordinary traveller would be nearly as ignorant of the behaviour of
glaciers as was the _Times_ correspondent referred to above, I fancy
the prophet would have been received with derision. Such, however, I
know to be the case; and only last year, while walking up Piz Languard
with a party of friends, I was asked if the medial moraine of the
Morteratsch glacier was a carriage road or only a bridle-path! This
is my excuse for entering at some length into a subject which has
been already written about in so able a manner and in much detail by
Professors Tyndall, Forbes, Heim, Forel, and others.
Now, let me tell you something about those great icy masses which,
under the name of glaciers, thrust their cold forms far below the
region of perpetual snow, and in some cases, as, for instance, that of
the Glacier des Bossons at Chamonix, even push down their frozen waves
amongst the meadows and forests in the very trough of the valley.
I am constantly asked by those who are only acquainted with the lower
end of the glaciers how it is that they are continually and rapidly
melting at their lower extremity, and yet their general features
are but slightly altered from year to year. The obvious answer is,
that they are constantly replenished from above, and that glacier
ice has formerly been snow, which, for a considerable period, has
been subjected to enormous pressure. The common illustration of a
snow-ball, squeezed in the hand till it becomes hard and icy, explains
this transition of snow to ice in a manner easily understood by all,
and if we remember that the warm hand, in addition to the pressure,
also tends to produce the above result, we have a parallel to the
heat of the sun acting on the cold, dry snow of the upper regions.
Now, every one knows that when it rains in the valleys it snows on
the mountains, and that even during the heat of summer it very seldom
rains above a height of 11,000 to 12,000 feet. In consequence of this,
the accumulation of snow on the higher peaks is very great, and the
pressure which is exerted by its weight is enormous.
As a natural result, a portion of the ice-caps or snow-beds gravitates
downwards, and where the upper snows are of great extent and the
shape of the channel suitable, a large glacier is found, as is the
case near Pontresina, where the huge Morteratsch glacier pursues its
lengthy course, fed by the snows of the Bernina and Bellavista. The
first to speak clearly and positively on the since well-proven theory
that a glacier moves like a river was Monseigneur Rendu, a native of
Savoy. “Between the Mer de Glace and a river there is a resemblance so
complete, that it is impossible to find in the latter a circumstance
which does not exist in the former,” he writes, and Professor Tyndall
sets forth in an admirable manner the reason why a glacier moves more
quickly in the centre than at the sides. I cannot do better than quote
his own words.
“A cork, when cast upon a stream near its centre, will move more
quickly than when thrown near the side, for the progress of the stream
is retarded by its banks. As you and your guide stood together on the
solid waves of that Amazon of ice, you were borne resistlessly along.
You saw the boulders perched upon their frozen pedestals; these were
the spoils of distant hills, quarried from summits far away, and
floated to lower levels like timber blocks upon the Rhone. As you
advanced towards the centre you were carried down the valley with an
ever-augmenting velocity. You felt it not--he felt it not--still you
were borne down with a velocity which, if continued, would amount to
1000 feet a year.”
Many glaciers descend in curves, pursuing a sinuous course towards the
valley, and the convex side of the curve must, of course, hurry up very
considerably in order to keep pace with the rest. Now, as the ice thus
moves faster on the one side than on the other, the result is that the
convex side is rent and torn asunder, and splits up into those cracks
and chasms known as crevasses. Consequently, a glacier which flows
downwards in a straight direction and at a gentle incline presents a
comparatively unbroken surface, while a glacier which descends in leaps
and bounds over a steep bed and dashes round sharp corners will exhibit
all the features of an impassable ice-fall.
Striking examples of the former class of glaciers are the Aletsch
glacier, the upper portion of the Gorner glacier, the Miage glacier,
the Roseg glacier, the Pasterzen glacier, &c., and of the latter the
Bies glacier, the Brenva glacier, the Géant glacier, the Pers glacier,
and many others. The exact point at which the snow of the heights
passes into glacier ice has never been definitely determined, but each
winter’s snowfall is distinctly traceable by a band of differently-hued
snow wherever above the snow-line a glacier is much split up.
High glacier-clad mountains are covered with what is known as
_névé_--_névé_ being the finely crystallised snow of the upper regions,
which remains unmelted all the summer. The glacier ice which is formed
by pressure of this _névé_ is quite different to the ice which results
from freezing water, and is found to consist of round crystals, varying
in size from that of a hen’s egg to that of the head of a pin. Any
observant person will have noticed the ice usually supplied at Swiss
_tables-d’hôtes_, and the curious way in which it behaves as compared
with ordinary ice; for while the latter melts uniformly from the
outside, the former is honeycombed with air and water, and after a time
its peculiar structure, composed of numerous particles, is noticeable.
These crystals or particles are known as _glacier granules_ or _glacier
corn_.
The whiteness of a glacier, as compared with the blackness of a frozen
lake, is a feature which I have known to puzzle many. It is simply
owing to the presence of this glacier corn, which allows a great
quantity of air to permeate the whole mass of the ice. The beautiful
blue veined or ribboned structure, first observed by Forbes on the
Unter-Aar glacier, is due to the absence of air-bubbles, and represents
bruises in the ice where, by melting, strain, and pressure, certain
parts have had the air driven out.
We will now notice several of the peculiarities which are conspicuous
on the surface of one of these great rivers of ice. As we walk up from,
say, the Morteratsch restaurant towards the glacier of that name, we
must cross part of the stony and earthy mass known as the terminal
moraine. Now the subject of moraines is a very large one, so much so,
that we shall probably devote nearly the whole of a future chapter
to it. For the present, we will merely walk over it, and get on to
the very dirty ice of which the snout or lower end of the Morteratsch
glacier is composed. As one of the party hews out the steps by which
you mount, you have time to observe the ice crystals or glacier corn
which we have already spoken of.
Before you have gone far on the level surface of the glacier, you will
see several boulders which are resting on ice pedestals supported at
some height. These are called _glacier tables_, and result from the
presence of a block of stone which protects the ice beneath it from
the heat of the sun, thus preventing it from melting. In consequence,
while the glacier all round has been dissolving and sinking, the ice
under these boulders has but slightly melted, and gradually a pillar
of sometimes as much as four feet or more in height is formed under
each erratic block. The sun is, of course, able to reach these ice
pedestals more freely on the south than on the north side, and thus we
observe that the boulder is not balanced evenly on the top, but always
inclines downwards towards the south side; it thus has been known to
render valuable aid to the mountaineer who has lost his way in a fog or
in the dark without a compass on a glacier, as he can, by observing the
position of a glacier table, easily inform himself of the direction
in which he is walking. Small stones have a different effect, as
they sink into the ice, leaving little holes. You will also probably
notice a line of sand-covered mounds, about four or five feet high,
and culminating in a sharp point or ridge. Scrape off a little of the
sand and earth, and you will find that the mound is composed of ice,
which looks quite black where you have uncovered it. The reason for
the existence of these dirt cones is obvious; the sand has protected
the ice, which has thus remained unmelted, and being heaped up thickly
in the centre and thinning off towards the sides, has thus taken its
sharply-pointed shape.
Continuing our walk up the glacier, we hear, gradually becoming louder
and louder as we approach, the roar of falling water, and soon we reach
a point where a bright, dancing stream leaps down a shaft in the ice
and is lost to sight. Be careful how you approach this deep hole (or,
as it is called, _moulin_), for one false step on your part would take
you down far beyond all human aid. Various persons have endeavoured to
gauge the thickness of a glacier at a given point by taking soundings
down a moulin, and Agassiz found no bottom at 260 metres in one on the
Unteraar glacier; he estimated the thickness of the ice to be 1509 feet
near the Abschwung. On Piz Roseg, where the hanging glaciers end in
abrupt ice-cliffs, a thickness of 250 feet has been observed. You are
now at the foot of the lower ice-fall of the Morteratsch glacier. We
will not go farther to-day, and we have already learnt how it is that
the tottering ice masses and grim crevasses are formed. We know that
the glacier on which we are standing is slowly moving downwards (by
its weight, and by sliding in its bed, especially facilitated by its
granular structure) at, roughly, the same rate as the _hour_-hand of an
ordinary watch. It has been estimated--I believe by Mr. Tuckett--that
a grain of snow would take 450 years to travel from the summit of the
Jungfrau to the termination of the Aletsch glacier. A most painful
illustration of the rate of motion of glaciers was furnished by the
descent in the ice of the Glacier des Bossons of the bodies of Dr.
Hamel’s three guides, who lost their lives on Mont Blanc in 1820, being
carried down the _Ancien Passage_ in an avalanche, and swept into
the _bergschrund_ at its base. On August 15, 1861, Ambrose Simond, a
Chamonix guide, who was accompanying a party of tourists to the lower
extremity of the Bossons glacier, noticed in one of the crevasses torn
pieces of clothes and some human bones. He brushed off the sand with
which they were covered, and brought them to Chamonix. Five men at
once started on hearing what he had found, and they discovered other
remains at a distance of some twelve or fifteen metres lower down. From
that day, the glacier continued to give back the remains of what it
had swallowed up forty-one years before, and what was found was beyond
doubt the bodies and belongings of Dr. Hamel’s guides. All that they
had carried with them, the scientific instruments, knapsacks, gloves,
&c., were gradually set free from their icy fetters. A gauze veil came
out untorn and not much faded; and the knapsack of Pierre Carrier
contained a leg of mutton perfectly recognisable. More remarkable than
anything else was the condition of a cork, which was not only still
stained by the wine, but also possessed a perceptible odour of the
contents of the bottle in which it had been fixed. (“Le Mont Blanc,” by
Charles Durier.)
But it is time to descend, and in the next chapter I will make a few
observations on _moraines_ and the power of a glacier in planing down
or removing whatever object it meets with; this power, as a matter of
fact, being very much more limited than is popularly supposed.