CHIEFLY NARRATIVE.
Ages are your days,
Ye grand expressors of the present tense
And types of permanence;
Firm ensigns of the fatal Being
Amid these coward shapes of joy and grief
That will not bide the seeing.
Hither we bring
Our insect miseries to the rocks,
And the whole flight with pestering wing
Vanish and end their murmuring,
Vanish beside these dedicated blocks.
Emerson
GLACIERS OF THE ALPS.
INTRODUCTORY.
(1.)
In the autumn of 1854 I attended the meeting of the British Association
at Liverpool; and, after it was over, availed myself of my position to
make an excursion into North Wales. Guided by a friend who knew the
country, I became acquainted with its chief beauties, and concluded the
expedition by a visit to Bangor and the neighbouring slate quarries of
Penrhyn.
From my boyhood I had been accustomed to handle slates; had seen them
used as roofing materials, and had worked the usual amount of arithmetic
upon them at school; but now, as I saw the rocks blasted, the broken
masses removed to the sheds surrounding the quarry, and there cloven
into thin plates, a new interest was excited, and I could not help
asking after the cause of this extraordinary property of cleavage. It
sufficed to strike the point of an iron instrument into the edge of a
plate of rock to cause the mass to yield and open, as wood opens in
advance of a wedge driven into it. I walked round the quarry and
observed that the planes of cleavage were everywhere parallel; the rock
was capable of being split in one direction only, and this direction
remained perfectly constant throughout the entire quarry.
[Sidenote: CLEAVAGE OF SLATE ROCKS.]
I was puzzled, and, on expressing my perplexity to my companion, he
suggested that the cleavage was nothing more than the layers in which
the rock had been originally deposited, and which, by some subsequent
disturbance, had been set on end, like the strata of the sandstone rocks
and chalk cliffs of Alum Bay. But though I was too ignorant to combat
this notion successfully, it by no means satisfied me. I did not know
that at the time of my visit this very question of slaty cleavage was
exciting the greatest attention among English geologists, and I quitted
the place with that feeling of intellectual discontent which, however
unpleasant it may be for a time, is very useful as a stimulant, and
perhaps as necessary to the true appreciation of knowledge as a healthy
appetite is to the enjoyment of food.
On inquiry I found that the subject had been treated by three English
writers, Professor Sedgwick, Mr. Daniel Sharpe, and Mr. Sorby. From
Professor Sedgwick I learned that cleavage and stratification were
things totally distinct from each other; that in many cases the strata
could be observed with the cleavage passing through them at a high
angle; and that this was the case throughout vast areas in North Wales
and Cumberland. I read the lucid and important memoir of this eminent
geologist with great interest: it placed the data of the problem before
me, as far as they were then known, and I found myself, to some extent
at least, in a condition to appreciate the value of a theoretic
explanation.
Everybody has heard of the force of gravitation, and of that of
cohesion; but there is a more subtle play of forces exerted by the
molecules of bodies upon each other when these molecules possess
sufficient freedom of action. In virtue of such forces, the ultimate
particles of matter are enabled to build themselves up into those
wondrous edifices which we call crystals. A diamond is a crystal
self-erected from atoms of carbon; an amethyst is a crystal built up
from particles of silica; Iceland spar is a crystal built by particles
of carbonate of lime. By artificial means we can allow the particles of
bodies the free play necessary to their crystallization. Thus a solution
of saltpetre exposed to slow evaporation produces crystals of saltpetre;
alum crystals of great size and beauty may be obtained in a similar
manner; and in the formation of a bit of common sugar-candy there are
agencies at play, the contemplation of which, as mere objects of
thought, is sufficient to make the wisest philosopher bow down in
wonder, and confess himself a child.
[Sidenote: CRYSTALLIZATION THEORY.]
The particles of certain crystalline bodies are found to arrange
themselves in layers, like courses of atomic masonry, and along these
layers such crystals may be easily cloven into the thinnest laminae. Some
crystals possess _one_ such direction in which they may be cloven, some
several; some, on the other hand, may be split with different facility
in different directions. Rock salt may be cloven with equal facility in
three directions at right angles to each other; that is, it may be split
into cubes; calcspar may be cloven in three directions oblique to each
other; that is, into rhomboids. Heavy spar may also be cloven in three
directions, but one cleavage is much more perfect, or more _eminent_ as
it is sometimes called, than the rest. Mica is a crystal which cleaves
very readily in one direction, and it is sufficiently tough to furnish
films of extreme tenuity: finally, any boy, with sufficient skill, who
tries a good crystal of sugar-candy in various directions with the blade
of his penknife, will find that it possesses one direction in
particular, along which, if the blade of the knife be placed and struck,
the crystal will split into plates possessing clean and shining surfaces
of cleavage.
[Sidenote: POLAR FORCES.]
Professor Sedgwick was intimately acquainted with all these facts, and a
great many more, when he investigated the cleavage of slate rocks; and
seeing no other explanation open to him, he ascribed to slaty cleavage a
crystalline origin. He supposed that the particles of slate rock were
acted on, after their deposition, by "polar forces," which so arranged
them as to produce the cleavage. According to this theory, therefore,
Honister Crag and the cliffs of Penrhyn are to be regarded as portions
of enormous crystals; a length of time commensurate with the vastness of
the supposed action being assumed to have elapsed between the deposition
of the rock and its final crystallization.
When, however, we look closely into this bold and beautiful hypothesis,
we find that the only analogy which exists between the physical
structure of slate rocks and of crystals is this single one of cleavage.
Such a coincidence might fairly give rise to the conjecture that both
were due to a common cause; but there is great difficulty in accepting
this as a theoretic truth. When we examine the structure of a slate
rock, we find that the substance is composed of the debris of former
rocks; that it was once a fine mud, composed of particles of _sensible
magnitude_. Is it meant that these particles, each taken as a whole,
were re-arranged after deposition? If so, the force which effected such
an arrangement must be wholly different from that of crystallization,
for the latter is essentially _molecular_. What is this force? Nature,
as far as we know, furnishes none competent, under the conditions, to
produce the effect. Is it meant that the molecules composing these
sensible particles have re-arranged themselves? We find no evidence of
such an action in the individual fragments: the mica is still mica, and
possesses all the properties of mica; and so of the other ingredients of
which the rock is composed. Independent of this, that an aggregate of
heterogeneous mineral fragments should, without any assignable external
cause, so shift its molecules as to produce a plane of cleavage common
to them all, is, in my opinion, an assumption too heavy for any theory
to bear.
Nevertheless, the paper of Professor Sedgwick invested the subject of
slaty cleavage with an interest not to be forgotten, and proved the
stimulus to further inquiry. The structure of slate rocks was more
closely examined; the fossils which they contained were subjected to
rigid scrutiny, and their shapes compared with those of the same species
taken from other rocks. Thus proceeding, the late Mr. Daniel Sharpe
found that the fossils contained in slate rocks are distorted in shape,
being uniformly flattened out in the direction of the planes of
cleavage. Here, then, was a fact of capital importance,--the shells
became the indicators of an action to which the mass containing them had
been subjected; they demonstrated the operation of pressure acting at
right angles to the planes of cleavage.
[Sidenote: MECHANICAL THEORY.]
The more the subject was investigated, the more clearly were the
evidences of pressure made out. Subsequent to Mr. Sharpe, Mr. Sorby
entered upon this field of inquiry. With great skill and patience he
prepared sections of slate rock, which he submitted to microscopic
examination, and his observations showed that the evidences of pressure
could be plainly traced, even in his minute specimens. The subject has
been since ably followed up by Professors Haughton, Harkness, and
others; but to the two gentlemen first mentioned we are, I think,
indebted for the prime facts on which rests the _mechanical theory_ of
slaty cleavage.[A]
[Sidenote: LECTURE AT THE ROYAL INSTITUTION.]
The observations just referred to showed the co-existence of the two
phenomena, but they did not prove that pressure and cleavage stood to
each other in the relation of cause and effect. "Can the pressure
produce the cleavage?" was still an open question, and it was one which
mere reasoning, unaided by experiment, was incompetent to answer.
Sharpe despaired of an experimental solution, regarding our means as
inadequate, and our time on earth too short to produce the result. Mr.
Sorby was more hopeful. Submitting mixtures of gypsum and oxide of iron
scales to pressure, he found that the scales set themselves
approximately at right angles to the direction in which the pressure was
applied. The position of the scales resembled that of the plates of mica
which his researches had disclosed to him in slate rock, and he inferred
that the presence of such plates, and of flat or elongated fragments
generally, lying all in the same general direction, was the cause of
slaty cleavage. At the meeting of the British Association at Glasgow, in
1855, I had the pleasure of seeing some of Mr. Sorby's specimens, and,
though the cleavage they exhibited was very rough, still, the tendency
to yield at right angles to the direction in which the pressure had been
applied, appeared sufficiently manifest.
At the time now referred to I was engaged, and had been for a long time
previously, in examining the effects of pressure upon the magnetic
force, and, as far back as 1851, I had noticed that some of the bodies
which I had subjected to pressure exhibited a cleavage of surpassing
beauty and delicacy. The bearing of such facts upon the present question
now forcibly occurred to me. I followed up the observations; visited
slate yards and quarries, observed the exfoliation of rails, the fibres
of iron, the structure of tiles, pottery, and cheese, and had several
practical lessons in the manufacture of puff-paste and other laminated
confectionery. My observations, I thought, pointed to a theory of slaty
cleavage different from any previously given, and which, moreover,
referred a great number of apparently unrelated phenomena to a common
cause. On the 10th of June, 1856, I made them the subject of a Friday
evening's discourse at the Royal Institution.[B]
[Sidenote: ORIGIN OF RESEARCHES.]
Such are the circumstances, apparently remote enough, under which my
connexion with glaciers originated. My friend Professor Huxley was
present at the lecture referred to: he was well acquainted with the work
of Professor Forbes, entitled 'Travels in the Alps,' and he surmised
that the question of slaty cleavage, in its new aspect, might have some
bearing upon the laminated structure of glacier-ice discussed in the
work referred to. He therefore urged me to read the 'Travels,' which I
did with care, and the book made the same impression upon me that it had
produced upon my friend. We were both going to Switzerland that year,
and it required but a slight modification of our plans to arrange a
joint excursion over some of the glaciers of the Oberland, and thus
afford ourselves the means of observing together the veined structure of
the ice.
Had the results of this arrangement been revealed to me beforehand, I
should have paused before entering upon an investigation which required
of me so long a renunciation of my old and more favourite pursuits. But
no man knows when he commences the examination of a physical problem
into what new and complicated mental alliances it may lead him. No
fragment of nature can be studied alone; each part is related to every
other part; and hence it is, that, following up the links of law which
connect phenomena, the physical investigator often finds himself led far
beyond the scope of his original intentions, the danger in this respect
augmenting in direct proportion to the wish of the inquirer to render
his knowledge solid and complete.
[Sidenote: A BOY'S BOOK.]
When the idea of writing this book first occurred to me, it was not my
intention to confine myself to the glaciers alone, but to make the work
a vehicle for the familiar explanation of such general physical
phenomena as had come under my notice. Nor did I intend to address it to
a cultured man of science, but to a youth of average intelligence, and
furnished with the education which England now offers to the young. I
wished indeed to make it a boy's class-book, which should reveal the
mode of life, as well as the scientific objects, of an explorer of the
Alps. The incidents of the past year have caused me to deviate, in some
degree, from this intention, but its traces will be sufficiently
manifest; and this reference to it will, I trust, excuse an occasional
liberty of style and simplicity of treatment which would be out of place
if intended for a reader of riper years.
FOOTNOTES:
[A] Mr. Sorby has drawn my attention to an able and interesting paper by
M. Bauer, in Karsten's 'Archiv' for 1846; in which it is announced that
cleavage is a tension of the mass _produced by pressure_. The author
refers to the experiments of Mr. Hopkins as bearing upon the question.
[B] See Appendix.
[Sidenote: THE OBERLAND. 1856.]
EXPEDITION OF 1856.
THE OBERLAND.
(2.)
On the 16th of August, 1856, I received my Alpenstock from the hands of
Dr. Hooker, in the garden of the Pension Ober, at Interlaken. It bore my
name, not marked, however, by the vulgar brands of the country, but by
the solar beams which had been converged upon it by the pocket lens of
my friend. I was the companion of Mr. Huxley, and our first aim was to
cross the Wengern Alp. Light and shadow enriched the crags and green
slopes as we advanced up the valley of Lauterbrunnen, and each occupied
himself with that which most interested him. My companion examined the
drift, I the cleavage, while both of us looked with interest at the
contortions of the strata to our left, and at the shadowy, unsubstantial
aspect of the pines, gleaming through the sunhaze to our right.
[Sidenote: FOLDED ROCKS. 1856.]
What was the physical condition of the rock when it was thus bent and
folded like a pliant mass? Was it necessarily softer than it is at
present? I do not think so. The shock which would crush a railway
carriage, if communicated to it at once, is harmless when distributed
over the interval necessary for the pushing in of the buffer. By
suddenly stopping a cock from which water flows you may burst the
conveyance pipe, while a slow turning of the cock keeps all safe. Might
not a solid rock by ages of pressure be folded as above? It is a
physical axiom that no body is perfectly hard, none perfectly soft, none
perfectly elastic. The hardest body subjected to pressure yields,
however little, and the same body when the pressure is removed cannot
return to its original form. If it did not yield in the slightest degree
it would be perfectly hard; if it could completely return to its
original shape it would be perfectly elastic.
Let a pound weight be placed upon a cube of granite; the cube is
flattened, though in an infinitesimal degree. Let the weight be removed,
the cube _remains_ a little flattened; it cannot quite return to its
primitive condition. Let us call the cube thus flattened No. 1. Starting
with No. 1 as a new mass, let the pound weight be laid upon it; the mass
yields, and on removing the weight it cannot return to the dimensions of
No. 1; we have a more flattened mass, No. 2. Proceeding in this manner,
it is manifest that by a repetition of the process we should produce a
series of masses, each succeeding one more flattened than the former.
This appears to be a necessary consequence of the physical axiom
referred to above.
Now if, instead of removing and replacing the weight in the manner
supposed, we cause it to rest continuously upon the cube, the
flattening, which above was intermittent, will be continuous; no matter
how hard the cube may be, there will be a gradual yielding of its mass
under the pressure. Apply this to squeezed rocks--to those, for example,
which form the base of an obelisk like the Matterhorn; that this base
must yield, seems a certain consequence of the physical constitution of
matter: the conclusion seems inevitable that the mountain is sinking by
its own weight. Let two points be fixed, one near the summit, the other
near the base of the obelisk; next year these points will have
approached each other. Whether the amount of approach in a human
lifetime be measureable we know not; but it seems certain that ages
would leave their impress upon the mass, and render visible to the eye
an action which at present is appreciable by the imagination only.
[Sidenote: THE JUNGFRAU AND SILBERHORN. 1856.]
We halted on the night of the 16th at the Jungfrau Hotel, and next
morning we saw the beams of the rising sun fall upon the peaked snow of
the Silberhorn. Slowly and solemnly the pure white cone appeared to rise
higher and higher into the sunlight, being afterwards mottled with gold
and gloom, as clouds drifted between it and the sun. I descended alone
towards the base of the mountain, making my way through a rugged gorge,
the sides of which were strewn with pine-trees, splintered, broken
across, and torn up by the roots. I finally reached the end of a
glacier, formed by the snow and shattered ice which fall from the
shoulders of the Jungfrau. The view from this place had a savage
magnificence such as I had not previously beheld, and it was not without
some slight feeling of awe that I clambered up the end of the glacier.
It was the first I had actually stood upon. The loneliness of the place
was very impressive, the silence being only broken by fitful gusts of
wind, or by the weird rattle of the debris which fell at intervals from
the melting ice.
[Sidenote: AVALANCHES. 1856.]
Once I noticed what appeared to be the sudden and enormous augmentation
of the waters of a cascade, but the sound soon informed me that the
increase was due to an avalanche which had chosen the track of the
cascade for its rush. Soon afterwards my eyes were fixed upon a white
slope some thousands of feet above me; I saw the ice give way, and,
after a sensible interval, the thunder of another avalanche reached me.
A kind of zigzag channel had been worn on the side of the mountain, and
through this the avalanche rushed, hidden at intervals, and anon
shooting forth, and leaping like a cataract down the precipices. The
sound was sometimes continuous, but sometimes broken into rounded
explosions which seemed to assert a passionate predominance over the
general level of the roar. These avalanches, when they first give way,
usually consist of enormous blocks of ice, which are more and more
shattered as they descend. Partly to the echoes of the first crash, but
mainly, I think, to the shock of the harder masses which preserve their
cohesion, the explosions which occur during the descent of the avalanche
are to be ascribed. Much of the ice is crushed to powder; and thus, when
an avalanche pours cataract-like over a ledge, the heavier masses, being
less influenced by the atmospheric resistance, shoot forward like
descending rockets, leaving the lighter powder in trains behind them.
Such is the material of which a class of the smaller glaciers in the
Alps is composed. They are the products of avalanches, the crushed ice
being recompacted into a solid mass, which exhibits on a smaller scale
most of the characteristics of the large glaciers.
After three hours' absence I reascended to the hotel, breakfasted, and
afterwards returned with Mr. Huxley to the glacier. While we were
engaged upon it the weather suddenly changed; lightning flashed about
the summits of the Jungfrau, and thunder "leaped" among her crags. Heavy
rain fell, but it cleared up afterwards with magical speed, and we
returned to our hotel. Heedless of the forebodings of many prophets of
evil weather we set out for Grindelwald. The scene from the summit of
the Little Scheideck was exceedingly grand. The upper air exhibited a
commotion which we did not experience; clouds were wildly driven against
the flanks of the Eiger, the Jungfrau thundered behind, while in front
of us a magnificent rainbow, fixing one of its arms in the valley of
Grindelwald, and, throwing the other right over the crown of the
Wetterhorn, clasped the mountain in its embrace. Through jagged
apertures in the clouds floods of golden light were poured down the
sides of the mountain. On the slopes were innumerable chalets,
glistening in the sunbeams, herds browsing peacefully and shaking their
mellow bells; while the blackness of the pine-trees, crowded into
woods, or scattered in pleasant clusters over alp and valley, contrasted
forcibly with the lively green of the fields.
[Sidenote: THE HEISSE PLATTE. 1856.]
At Grindelwald, on the 18th, we engaged a strong and competent guide,
named Christian Kaufmann, and proceeded to the Lower Glacier. After a
steep ascent, we gained a point from which we could look down upon the
frozen mass. At first the ice presented an appearance of utter
confusion, but we soon reached a position where the mechanical
conditions of the glacier revealed themselves, and where we might learn,
had we not known it before, that confusion is merely the unknown
intermixture of laws, and becomes order and beauty when we rise to their
comprehension. We reached the so-called Eismeer--Ice Sea. In front of us
was the range of the Viescherhoerner, and a vast snow slope, from which
one branch of the glacier was fed. Near the base of this _neve_, and
surrounded on all sides by ice, lay a brown rock, to which our attention
was directed as a place noted for avalanches; on this rock snow or ice
never rests, and it is hence called the _Heisse Platte_--the Hot Plate.
At the base of the rock, and far below it, the glacier was covered with
clean crushed ice, which had fallen from a crown of frozen cliffs
encircling the brow of the rock. One obelisk in particular signalised
itself from all others by its exceeding grace and beauty. Its general
surface was dazzling white, but from its clefts and fissures issued a
delicate blue light, which deepened in hue from the edges inwards. It
stood upon a pedestal of its own substance, and seemed as accurately
fixed as if rule and plummet had been employed in its erection. Fig. 1
represents this beautiful minaret of ice.
[Sidenote: ICE MINARET. 1856.]
[Illustration: Fig. 1. Ice Minaret.]
While we were in sight of the Heisse Platte, a dozen avalanches rushed
downwards from its summit. In most cases we were informed of the descent
of an avalanche by the sound, but sometimes the white mass was seen
gliding down the rock, and scattering its _smoke_ in the air, long
before the sound reached us. It is difficult to reconcile the
insignificant appearance presented by avalanches, when seen from a
distance, with the volume of sound which they generate; but on this day
we saw sufficient to account for the noise. One block of solid ice which
we found below the Heisse Platte measured 7 feet 6 inches in length, 5
feet 8 inches in height, and 4 feet 6 inches in depth. A second mass was
10 feet long, 8 feet high, and 6 feet wide. It contained therefore 480
cubic feet of ice, which had been cast to a distance of nearly 1000
yards down the glacier. The shock of such hard and ponderous projectiles
against rocks and ice, reinforced by the echoes from the surrounding
mountains, will appear sufficient to account for the peals by which
their descent is accompanied.
[Sidenote: ECHOES OF THE WETTERHORN. 1856.]
A second day, in company with Dr. Hooker, completed the examination of
this glacier in 1856; after which I parted from my friends, Mr. Huxley
intending to rejoin me at the Grimsel. On the morning of the 20th of
August I strapped on my knapsack and ascended the green slopes from
Grindelwald towards the Great Scheideck. Before reaching the summit I
frequently heard the wonderful echoes of the Wetterhorn. Some travellers
were in advance of me, and to amuse them an alpine horn was blown. The
direct sound was cut off from me by a hill, but the echoes talked down
to me from the mountain walls. The sonorous waves arrived after one,
two, three, and more reflections, diminishing gradually in intensity,
but increasing in softness, as if in its wanderings from crag to crag
the sound had undergone a kind of sifting process, leaving all its
grossness behind, and returning in delightful flute notes to the ear.
Let us investigate this point a little. If two looking-glasses be placed
perfectly parallel to each other, with a lighted candle between them, an
infinite series of images of the candle will be seen at both sides, the
images diminishing in brightness the further they recede. But if the
looking-glasses, instead of being parallel, enclose an angle, a limited
number of images only will be seen. The smaller the angle which the
reflectors make with each other, or, in other words, the nearer they
approach parallelism, the greater will be the number of images observed.
To find the number of images the following is the rule:--Divide 360, or
the number of degrees in a circle, by the number of degrees in the angle
enclosed by the two mirrors, the quotient will be _one more_ than the
number of images; or, counting the object itself, the quotient is always
equal to the number of images plus the object. In Fig. 2 I have given
the number and position of the images produced by two mirrors placed at
an angle of 45 deg. A B and B C mark the edges of the mirrors, and 0
represents the candle, which, for the sake of simplicity, I have placed
midway between them. Fix one point of a pair of compasses at B, and with
the distance B 0 sweep a circle:--_all the images will be ranged upon
the circumference of this circle_. The number of images found by the
foregoing rule is 7, and their positions are marked in the figure by the
numbers 1, 2, 3, &c.
[Illustration: Fig. 2. Diagram of an angular reflector.]
[Sidenote: ECHOES EXPLAINED. 1856.]
Suppose the _ear_ to occupy the place of the eye, and that _a sounding
body_ occupies the place of the luminous one, we should then have just
as many _echoes_ as we had _images_ in the former case. These echoes
would diminish in loudness just as the images of the candle diminish in
brightness. At each reflection a portion both of sound and light is
lost; hence the oftener light is reflected the dimmer it becomes, and
the oftener sound is reflected the fainter it is.
Now the cliffs of the Wetterhorn are so many rough angular reflectors of
the sound: some of them send it back directly to the listener, and we
have a first echo; some of them send it on to others from which it is
again reflected, forming a second echo. Thus, by repeated reflection,
successive echoes are sent to the ear, until, at length, they become so
faint as to be inaudible. The sound, as it diminishes in intensity,
appears to come from greater and greater distances, as if it were
receding into the mountain solitudes; the final echoes being
inexpressibly soft and pure.
[Sidenote: REICHENBACH AND HANDECK. 1856.]
After crossing the Scheideck I descended to Meyringen, visiting the
Reichenbach waterfall on my way. A peculiarity of the descending water
here is, that it is broken up in one of the basins into nodular masses,
each of which in falling leaves the light foaming mass which surrounds
it as a train in the air behind; the effect exactly resembles that of
the avalanches of the Jungfrau, in which the more solid blocks of ice
shoot forward in advance of the lighter debris, which is held back by
the friction of the air.
Next day I ascended the valley of Hasli, and observed upon the rocks and
mountains the action of ancient glaciers which once filled the valley to
the height of more than a thousand feet above its present level. I
paused, of course, at the waterfall of Handeck, and stood for a time
upon the wooden bridge which spans the river at its top. The Aar comes
gambolling down to the bridge from its parent glacier, takes one short
jump upon a projecting ledge, boils up into foam, and then leaps into a
chasm, from the bottom of which its roar ascends through the gloom. A
rivulet named the Aarlenbach joins the Aar from the left in the very
jaws of the chasm: falling, at first, upon a projection at some depth
below the edge, and, rebounding from this, it darts at the Aar, and both
plunge together like a pair of fighting demons to the bottom of the
gorge. The foam of the Aarlenbach is white, that of the Aar is yellow,
and this enables the observer to trace the passage of the one cataract
_through_ the other. As I stood upon the bridge the sun shone brightly
upon the spray and foam; my shadow was oblique to the river, and hence a
symmetrical rainbow could not be formed in the spray, but one half of a
lovely bow, with its base in the chasm, leaned over against the opposite
rocks, the colours advancing and retreating as the spray shifted its
position. I had been watching the water intently for some time, when a
little Swiss boy, who stood beside me, observed, in his trenchant
German, "There plunge stones ever downwards." The stones were palpable
enough, carried down by the cataract, and sometimes completely breaking
loose from it, but I did not see them until my attention was withdrawn
from the water.
[Sidenote: HUT OF M. DOLLFUSS. 1856.]
On my arrival at the Grimsel I found Mr. Huxley already there, and,
after a few minutes' conversation, we decided to spend a night in a hut
built by M. Dollfuss in 1846, beside the Unteraar glacier, about 2000
feet above the Hospice. We hoped thus to be able to examine the glacier
to its origin on the following day. Two days' food and some blankets
were sent up from the Hospice, and, accompanied by our guide, we
proceeded to the glacier.
[Sidenote: HOTEL DES NEUFCHATELOIS. 1856.]
Having climbed a great terminal moraine, and tramped for a considerable
time amid loose shingle and boulders, we came upon the ice. The finest
specimens of "tables" which I have ever seen are to be found upon this
glacier--huge masses of clean granite poised on pedestals of ice. Here
are also "dirt-cones" of the largest size, and numerous shafts, the
forsaken passages of ancient "moulins," some filled with water, others
simply with deep blue light. I reserve the description and explanation
of both cones and moulins for another place. The surfaces of some of the
small pools were sprinkled lightly over with snow, which the water
underneath was unable to melt; a coating of snow granules was thus
formed, flexible as chain armour, but so close that the air could not
escape through it. Some bubbles which had risen through the water had
lifted the coating here and there into little rounded domes, which, by
gentle pressure, could be shifted hither and thither, and several of
them collected into one. We reached the hut, the floor of which appeared
to be of the original mountain slab; there was a space for cooking
walled off from the sleeping-room, half of which was raised above the
floor, and contained a quantity of old hay. The number 2404 metres, the
height, I suppose, of the place above the sea, was painted on the
door, behind which were also the names of several well-known
observers--Agassiz, Forbes, Desor, Dollfuss, Ramsay, and others--cut in
the wood. A loft contained a number of instruments for boring, a
surveyor's chain, ropes, and other matters. After dinner I made my way
alone towards the junction of the Finsteraar and Lauteraar glaciers,
which unite at the Abschwung to form the trunk stream of the Unteraar
glacier. Upon the great central moraine which runs between the branches
were perched enormous masses of rock, and, under the overhanging ledge
of one of these, M. Agassiz had his _Hotel des Neufchatelois_. The rock
is still there, bearing traces of names now nearly obliterated by the
weather, while the fragments around also bear inscriptions. There in the
wilderness, in the gray light of evening, these blurred and faded
evidences of human activity wore an aspect of sadness. It was a temple
of science now in ruins, and I a solitary pilgrim to the desecrated
blocks. As the day declined, rain began to fall, and I turned my face
towards my new home; where in due time we betook ourselves to our hay,
and waited hopefully for the morning.
But our hopes were doomed to disappointment. A vast quantity of snow
fell during the night, and, when we arose, we found the glacier covered,
and the air thick with the descending flakes. We waited, hoping that it
might clear up, but noon arrived and passed without improvement; our
fire-wood was exhausted, the weather intensely cold, and, according to
the men's opinion, hopelessly bad; they opposed the idea of ascending
further, and we had therefore no alternative but to pack up and move
downwards. What was snow at the higher elevations changed to rain lower
down, and drenched us completely before we reached the Grimsel. But
though thus partially foiled in our design, this visit taught us much
regarding the structure and general phenomena of the glacier.
[Sidenote: THE RHONE GLACIER. 1856.]
The morning of the 24th was clear and calm: we rose with the sun,
refreshed and strong, and crossed the Grimsel pass at an early hour. The
view from the summit of the pass was lovely in the extreme; the sky a
deep blue, the surrounding summits all enamelled with the newly-fallen
snow, which gleamed with dazzling whiteness in the sunlight. It was
Sunday, and the scene was itself a Sabbath, with no sound to disturb its
perfect rest. In a lake which we passed the mountains were mirrored
without distortion, for there was no motion of the air to ruffle its
surface. From the summit of the Mayenwand we looked down upon the Rhone
glacier, and a noble object it seemed,--I hardly know a finer of its
kind in the Alps. Forcing itself through the narrow gorge which holds
the ice cascade in its jaws, and where it is greatly riven and
dislocated, it spreads out in the valley below in such a manner as
clearly to reveal to the mind's eye the nature of the forces to which it
is subjected. Longfellow's figure is quite correct; the glacier
resembles a vast gauntlet, of which the gorge represents the wrist;
while the lower glacier, cleft by its fissures into finger-like ridges,
is typified by the hand.
Furnishing ourselves with provisions at the adjacent inn, we devoted
some hours to the examination of the lower portion of the glacier. The
dirt upon its surface was arranged in grooves as fine as if produced by
the passage of a rake, while the laminated structure of the deeper ice
always corresponded to the superficial grooving. We found several
shafts, some empty, some filled with water. At one place our attention
was attracted by a singular noise, evidently produced by the forcing of
air and water through passages in the body of the glacier; the sound
rose and fell for several minutes, like a kind of intermittent snore,
reminding one of Hugi's hypothesis that the glacier was alive.
[Sidenote: RINGS AROUND THE SUN. 1856.]
We afterwards climbed to a point from which the whole glacier was
visible to us from its origin to its end. Adjacent to us rose the mighty
mass of the Finsteraarhorn, the monarch of the Oberland. The Galenstock
was also at hand, while round about the _neve_ of the glacier a mountain
wall projected its jagged outline against the sky. At a distance was the
grand cone of the Weisshorn, then, and I believe still, unscaled;[A]
further to the left the magnificent peaks of the Mischabel; while
between them, in savage isolation, stood the obelisk of the Matterhorn.
Near us was the chain of the Furca, all covered with shining snow, while
overhead the dark blue of the firmament so influenced the general scene
as to inspire a sentiment of wonder approaching to awe. We descended to
the glacier, and proceeded towards its source. As we advanced an unusual
light fell upon the mountains, and looking upwards we saw a series of
coloured rings, drawn like a vivid circular rainbow quite round the sun.
Between the orb and us spread a thin veil of cloud on which the circles
were painted; the western side of the veil soon melted away, and with it
the colours, but the eastern half remained a quarter of an hour longer,
and then in its turn disappeared. The crevasses became more frequent and
dangerous as we ascended. They were usually furnished with overhanging
eaves of snow, from which long icicles depended, and to tread on which
might be fatal. We were near the source of the glacier, but the time
necessary to reach it was nevertheless indefinite, so great was the
entanglement of fissures. We followed one huge chasm for some hundreds
of yards, hoping to cross it; but after half an hour's fruitless effort
we found ourselves baffled and forced to retrace our steps.
[Sidenote: SPIRIT OF THE BROCKEN. 1856.]
The sun was sloping to the west, and we thought it wise to return; so
down the glacier we went, mingling our footsteps with the tracks of
chamois, while the frightened marmots piped incessantly from the rocks.
We reached the land once more, and halted for a time to look upon the
scene within view. The marvellous blueness of the sky in the earlier
part of the day indicated that the air was charged, almost to
saturation, with transparent aqueous vapour. As the sun sank the shadow
of the Finsteraarhorn was cast through the adjacent atmosphere, which,
thus deprived of the direct rays, curdled up into visible fog. The
condensed vapour moved slowly along the flanks of the mountain, and
poured itself cataract-like into the valley of the Rhone. Here it met
the sun again, which reduced it once more to the invisible state. Thus,
though there was an incessant supply from the generator behind, the fog
made no progress; as in the case of the moving glacier, the end of the
cloud-river remained stationary where consumption was equal to supply.
Proceeding along the mountain to the Furca, we found the valley at the
further side of the pass also filled with fog, which rose, like a wall,
high above the region of actual shadow. Once on turning a corner an
exclamation of surprise burst simultaneously from my companion and
myself. Before each of us and against the wall of fog, stood a spectral
image of a man, of colossal dimensions; dark as a whole, but bounded by
a coloured outline. We stretched forth our arms; the spectres did the
same. We raised our alpenstocks; the spectres also flourished their
batons. All our actions were imitated by these fringed and gigantic
shades. We had, in fact, _the Spirit of the Brocken_ before us in
perfection.
At the time here referred to I had had but little experience of alpine
phenomena. I had been through the Oberland in 1850, but was then too
ignorant to learn much from my excursion. Hence the novelty of this
day's experience may have rendered it impressive: still even now I think
there was an intrinsic grandeur in its phenomena which entitles the day
to rank with the most remarkable that I have spent among the Alps. At
the Furca, to my great regret, the joint ramblings of my friend and
myself ended; I parted from him on the mountain side, and watched him
descending, till the gray of evening finally hid him from my view.
FOOTNOTES:
[A] The Weisshorn was first scaled, by Tyndall, in 1861.--L. C. T.
[Sidenote: THE TYROL. 1856.]
THE TYROL.
(3.)
My subsequent destination was Vienna; but I wished to associate with my
journey thither a visit to some of the glaciers of the Tyrol. At
Landeck, on the 29th of August, I learned that the nearest glacier was
that adjacent to the Gebatsch Alp, at the head of the Kaunserthal; and
on the following morning I was on my way towards this valley. I sought
to obtain a guide at Kaltebrunnen, but failed; and afterwards walked to
the little hamlet of Feuchten, where I put up at a very lonely inn. My
host, I believe, had never seen an Englishman, but he had heard of such,
and remarked to me in his patois with emphasis, "_Die Englaender sind die
kuehnsten Leute in dieser Welt._" Through his mediation I secured a
chamois-hunter, named Johann Auer, to be my guide, and next morning I
started with this man up the valley. The sun, as we ascended, smote the
earth and us with great power; high mountains flanked us on either side,
while in front of us, closing the view, was the mass of the Weisskugel,
covered with snow. At three o'clock we came in sight of the glacier,
and soon afterwards I made the acquaintance of the _Senner_ or
cheesemakers of the Gebatsch Alp.
[Sidenote: THE GEBATSCH ALP. 1856.]
The chief of these was a fine tall fellow, with free, frank countenance,
which, however, had a dash of the mountain wildness in it. His feet were
bare, he wore breeches, and fragments of stockings partially covered his
legs, leaving a black zone between the upper rim of the sock and the
breeches. His feet and face were of the same swarthy hue; still he was
handsome, and in a measure pleasant to look upon. He asked me what he
could cook for me, and I requested some bread and milk; the former was a
month old, the latter was fresh and delicious, and on these I fared
sumptuously. I went to the glacier afterwards with my guide, and
remained upon the ice until twilight, when we returned, guided by no
path, but passing amid crags grasped by the gnarled roots of the pine,
through green dells, and over bilberry knolls of exquisite colouring. My
guide kept in advance of me singing a Tyrolese melody, and his song and
the surrounding scene revived and realised all the impressions of my
boyhood regarding the Tyrol.
Milking was over when we returned to the chalet, which now contained
four men exclusive of myself and my guide. A fire of pine logs was made
upon a platform of stone, elevated three feet above the floor; there was
no chimney, as the smoke found ample vent through the holes and fissures
in the sides and roof. The men were all intensely sunburnt, the
legitimate brown deepening into black with beard and dirt. The chief
senner prepared supper, breaking eggs into a dish, and using his black
fingers to empty the shell when the albumen was refractory. A fine erect
figure he was as he stood in the glowing light of the fire. All the men
were smoking, and now and then a brand was taken from the fire to light
a renewed pipe, and a ruddy glare flung thereby over the wild
countenance of the smoker. In one corner of the chalet, and raised high
above the ground, was a large bed, covered with clothes of the most
dubious black-brown hue; at one end was a little water-wheel turned by a
brook, which communicated motion to a churndash which made the butter.
The beams and rafters were covered with cheeses, drying in the warm
smoke. The senner, at my request, showed me his storeroom, and explained
to me the process of making cheese, its interest to me consisting in its
bearing upon the question of slaty cleavage. Three gigantic masses of
butter were in the room, and I amused my host by calling them
butter-glaciers. Soon afterwards a bit of cotton was stuck in a lump of
grease, which was placed in a lantern, and the wick ignited; the
chamois-hunter took it, and led the way to our resting-place, I having
previously declined a good-natured invitation to sleep in the big black
bed already referred to.
[Sidenote: AN ALPINE CHALET. 1856.]
There was a cowhouse near the chalet, and above it, raised on pillars of
pine, and approached by a ladder, was a loft, which contained a quantity
of dry hay: this my guide shook to soften the lumps, and erected an
eminence for my head. I lay down, drawing my plaid over me, but Auer
affirmed that this would not be a sufficient protection against the
cold; he therefore piled hay upon me to the shoulders, and proposed
covering up my head also. This, however, I declined, though the biting
coldness of the air, which sometimes blew in upon us, afterwards proved
to me the wisdom of the suggestion. Having set me right, my
chamois-hunter prepared a place for himself, and soon his heavy
breathing informed me that he was in a state of bliss which I could only
envy. One by one the stars crossed the apertures in the roof. Once the
Pleiades hung above me like a cluster of gems; I tried to admire them,
but there was no fervour in my admiration. Sometimes I dozed, but
always as this was about to deepen into positive sleep it was rudely
broken by the clamour of a group of pigs which occupied the ground-floor
of our dwelling. The object of each individual of the group was to
secure for himself the maximum amount of heat, and hence the outside
members were incessantly trying to become inside ones. It was the
struggle of radical and conservative among the pachyderms, the politics
being determined by the accident of position.
[Sidenote: THE GEBATSCH GLACIER. 1856.]
I rose at five o'clock on the 1st of September, and after a breakfast of
black bread and milk ascended the glacier as far as practicable. We once
quitted it, crossed a promontory, and descended upon one of its
branches, which was flanked by some fine old moraines. We here came upon
a group of seven marmots, which with yells of terror scattered
themselves among the rocks. The points of the glacier beyond my reach I
examined through a telescope; along the faces of the sections the lines
of stratification were clearly shown; and in many places where the mass
showed manifest signs of lateral pressure, I thought I could observe the
cleavage passing though the strata. The point, however, was too
important to rest upon an observation made from such a distance, and I
therefore abstained from mentioning it subsequently. I examined the
fissures and the veining, and noticed how the latter became most perfect
in places where the pressure was greatest. The effect of _oblique_
pressure was also finely shown: at one place the thrust of the
descending glacier was opposed by the resistance offered by the side of
the valley, the direction of the force being oblique to the side; the
consequence was a structure nearly parallel to the valley, and
consequently oblique to the thrust which I believe to be its cause.
[Sidenote: A CHAMOIS ON THE ROCKS. 1856.]
After five hours' examination we returned to our chalet, where we
refreshed ourselves, put our things in order, and faced a nameless
"Joch," or pass; our aim being to cross the mountains into the valley of
Lantaufer, and reach Graun that evening. After a rough ascent over the
alp we came to the dead crag, where the weather had broken up the
mountains into ruinous heaps of rock and shingle. We reached the end of
a glacier, the ice of which was covered by sloppy snow, and at some
distance up it came upon an islet of stones and debris, where we paused
to rest ourselves. My guide, as usual, ranged over the summits with his
telescope, and at length exclaimed, "I see a chamois." The creature
stood upon a cliff some hundreds of yards to our left, and seemed to
watch our movements. It was a most graceful animal, and its life and
beauty stood out in forcible antithesis to the surrounding savagery and
death.
On the steep slopes of the glacier I was assisted by the hand of my
guide. In fact, on this day I deemed places dangerous, and dreaded them
as such, which subsequent practice enabled me to regard with perfect
indifference; so much does what we call courage depend upon habit, or on
the fact of knowing that we have really nothing to fear. Doubtless there
are times when a climber has to make up his mind for very unpleasant
possibilities, and even gather calmness from the contemplation of the
worst; but in most cases I should say that his courage is derived from
the latent feeling that the chances of safety are immensely in his
favour.
[Sidenote: PASSAGE OF A JOCH. 1856.]
After a tough struggle we reached the narrow row of crags which form the
crest of the pass, and looked into the world of mountain and cloud on
the other side. The scene was one of stern grandeur--the misty lights
and deep cloud-glooms being so disposed as to augment the impression of
vastness which the scene conveyed. The breeze at the summit was
exceedingly keen, but it gave our muscles tone, and we sprang swiftly
downward through the yielding debris which here overlies the mountain,
and in which we sometimes sank to the knees. Lower down we came once
more upon the ice. The glacier had at one place melted away from its
bounding cliff, which rose vertically to our right, while a wall of ice
60 or 80 feet high was on our left. Between the two was a narrow
passage, the floor of which was snow, which I knew to be hollow beneath:
my companion, however, was in advance of me, and he being the heavier
man, where he trod I followed without hesitation. On turning an angle of
the rock I noticed an expression of concern upon his countenance, and he
muttered audibly, "I did not expect this." The snow-floor had, in fact,
given way, and exposed to view a clear green lake, one boundary of which
was a sheer precipice of rock, and the other the aforesaid wall of ice;
the latter, however, curved a little at its base, so as to form a short
steep slope which overhung the water. My guide first tried the slope
alone; biting the ice with his shoe-nails, and holding on by the spike
of his baton, he reached the other side. He then returned, and,
divesting myself of all superfluous clothes, as a preparation for the
plunge which I fully expected, I also passed in safety. Probably the
consciousness that I had water to fall into instead of pure space,
enabled me to get across without anxiety or mischance; but had I, like
my guide, been unable to swim, my feelings would have been far
different.
This accomplished, we went swiftly down the valley, and the more I saw
of my guide the more I liked him. He might, if he wished, have made his
day's journey shorter by stopping before he reached Graun, but he would
not do so. Every word he said to me regarding distances was true, and
there was not the slightest desire shown to magnify his own labour. I
learnt by mere accident that the day's work had cut up his feet, but his
cheerfulness and energy did not bate a jot till he had landed me in the
Black Eagle at Graun. Next morning he came to my room, and said that he
felt sufficiently refreshed to return home. I paid him what I owed him,
when he took my hand, and, silently bending down his head, kissed it;
then, standing erect, he stretched forth his right hand, which I grasped
firmly in mine, and bade him farewell; and thus I parted from Johann
Auer, my brave and truthful chamois-hunter.
On the following day I met Dr. Frankland in the Finstermuntz pass, and
that night we bivouacked together at Mals. Heavy rain fell throughout
the night, but it came from a region high above that of liquidity. It
was first snow, which, as it descended through the warmer strata of the
atmosphere, was reduced to water. Overhead, in the air, might be traced
a surface, below which the precipitate was liquid, above which it was
solid; and this surface, intersecting the mountains which surround Mals,
marked upon them a beautifully-defined _snow-line_, below which the
pines were dark and the pastures green, but above which pines and
pastures and crags were covered with the freshly-fallen snow.
[Sidenote: THE STELVIO. 1856.]
[Sidenote: COLOUR OF FRESH SNOW. 1856.]
On the 2nd of September we crossed the Stelvio. The brown cone of the
well-known Madatschspitze was clear, but the higher summits were
clouded, and the fragments of sunshine which reached the lower world
wandered like gleams of fluorescent light over the glaciers. Near the
snow-line the partial melting of the snow had rendered it coarsely
granular, but as we ascended it became finer, and the light emitted from
its cracks and cavities a pure and deep blue. When a staff was driven
into the snow low down the mountain, the colour of the light in the
orifice was scarcely sensibly blue, but higher up this increased in a
wonderful degree, and at the summit the effect was marvellous. I struck
my staff into the snow, and turned it round and round; the surrounding
snow cracked repeatedly, and flashes of blue light issued from the
fissures. The fragments of snow that adhered to the staff were, by
contrast, of a beautiful pink yellow, so that, on moving the staff with
such fragments attached to it up and down, it was difficult to resist
the impression that a pink flame was ascending and descending in the
hole. As we went down the other side of the pass, the effect became more
and more feeble, until, near the snow-line, it almost wholly
disappeared.
We remained that night at the baths of Bormio, but the following
afternoon being fine we wished to avail ourselves of the fair weather to
witness the scene from the summit of the pass. Twilight came on before
we reached Santa Maria, but a gorgeous orange overspread the western
horizon, from which we hoped to derive sufficient light. It was a little
too late when we reached the top, but still the scene was magnificent. A
multitude of mountains raised their crowns towards heaven, while above
all rose the snow-white cone of the Ortler. Far into the valley the
giant stretched his granite limbs, until they were hid from us by
darkness. As this deepened, the heavens became more and more crowded
with stars, which blazed like gems over the heads of the mountains. At
times the silence was perfect, unbroken save by the crackling of the
frozen snow beneath our own feet; while at other times a breeze would
swoop down upon us, keen and hostile, scattering the snow from the roofs
of the wooden galleries in frozen powder over us. Long after night had
set in, a ghastly gleam rested upon the summit of the Ortler, while the
peaks in front deepened to a dusky neutral tint, the more distant ones
being lost in gloom. We descended at a swift pace to Trafoi, which we
reached before 11 P.M.
[Sidenote: SINGULAR HAILSTORM. 1856.]
Meran was our next resting-place, whence we turned through the
Schnalzerthal to Unserfrau, and thence over the Hochjoch to Fend. From
a religious procession we took a guide, who, though partly intoxicated,
did his duty well. Before reaching the summit of the pass we were
assailed by a violent hailstorm, each hailstone being a frozen cone with
a rounded end. Had not their motion through the air something to do with
the shape of these hailstones? The theory of meteorites now generally
accepted is that they are small planetary bodies drawn to the earth by
gravity, and brought to incandescence by friction against the earth's
atmosphere. Such a body moving through the atmosphere must have
condensed hot air in front of it, and rarefied cool air behind it; and
the same is true to a small extent of a hailstone. This distribution of
temperature must, I imagine, have some influence on the shape of the
stone. Possibly also the stratified appearance of some hailstones may be
connected with this action.[A]
[Sidenote: THE HOCHJOCH AND FEND. 1856.]
The hail ceased and the heights above us cleared as we ascended. At the
top of the pass we found ourselves on the verge of a great _neve_, which
lay between two ranges of summits, sloping down to the base of each
range from a high and rounded centre: a wilder glacier scene I have
scarcely witnessed. Wishing to obtain a more perfect view of the region,
I diverged from the track followed by Dr. Frankland and the guide, and
climbed a ridge of snow about half a mile to the right of them. A
glorious expanse was before me, stretching itself in vast undulations,
and heaping itself here and there into mountainous cones, white and
pure, with the deep blue heaven behind them. Here I had my first
experience of hidden crevasses, and to my extreme astonishment once
found myself in the jaws of a fissure of whose existence I had not the
slightest notice. Such accidents have often occurred to me since, but
the impression made by the first is likely to remain the strongest. It
was dark when we reached the wretched Wirthshaus at Fend, where, badly
fed, badly lodged, and disturbed by the noise of innumerable rats, we
spent the night. Thus ended my brief glacier expedition of 1856; and on
the observations then made, and on subsequent experiments, was founded a
paper presented to the Royal Society by Mr. Huxley and myself.[B]
FOOTNOTES:
[A] I take the following account of a grander storm of the above
character from Hooker's 'Himalayan Journals,' vol. ii. p. 405.
"On the 20th (March, 1849) we had a change in the weather: a violent
storm from the south-west occurred at noon, with hail of a strange form,
the stones being sections of hollow spheres, half an inch across and
upwards, formed of cones with truncated apices and convex bases: these
cones were aggregated together with their bases outwards. The large
masses were followed by a shower of the separate conical pieces, and
that by heavy rain. On the mountains this storm was most severe: the
stones lay at Darjeeling for seven days, congealed into masses of ice
several feet long and a foot thick in sheltered places: at Purneah,
fifty miles south, stones one and two inches across fell, probably as
whole spheres."
[B] 'Phil. Trans.' 1857, pp. 327-346.--L. C. T.
[Sidenote: THE LAKE OF GENEVA. 1857.]
EXPEDITION OF 1857.
THE LAKE OF GENEVA.
(4.)
The time occupied in the observations of 1856 embraced about five whole
days; and though these days were laborious and instructive, still so
short a time proved to be wholly incommensurate with the claims of so
wide a problem. During the subsequent experimental treatment of the
subject, I had often occasion to feel the incompleteness of my
knowledge, and hence arose the desire to make a second expedition to the
Alps, for the purpose of expanding, fortifying, or, if necessary,
correcting first impressions.
On Thursday, the 9th of July, 1857, I found myself upon the Lake of
Geneva, proceeding towards Vevey. I had long wished to see the waters of
this renowned inland sea, the colour of which is perhaps more
interesting to the man of science than to the poets who have sung about
it. Long ago its depth of blue excited attention, but no systematic
examination of the subject has, so far as I know, been attempted. It may
be that the lake simply exhibits the colour of pure water. Ice is blue,
and it is reasonable to suppose that the liquid obtained from the fusion
of ice is of the same colour; but still the question presses--"Is the
blue of the Lake of Geneva to be entirely accounted for in this way?"
The attempts which have been made to explain it otherwise show that at
least a doubt exists as to the sufficiency of the above explanation.
[Sidenote: BLUENESS OF THE WATER. 1857.]
It is only in its deeper portions that the colour of the lake is
properly seen. Where the bottom comes into view the pure effect of the
water is disturbed; but where the water is deep the colour is deep:
between Rolle and Nyon for example, the blue is superb. Where the blue
was deepest, however, it gave me the impression of turbidity rather than
of deep transparency. At the upper portion of the lake the water through
which the steamer passed was of a blue green. Wishing to see the place
where the Rhone enters the lake, I walked on the morning of the 10th
from Villeneuve to Novelle, and thence through the woods to the river
side. Proceeding along an embankment, raised to defend the adjacent land
from the incursions of the river, an hour brought me to the place where
it empties itself into the lake. The contrast between the two waters was
very great: the river was almost white with the finely divided matter
which it held in suspension; while the lake at some distance was of a
deep ultramarine.
The lake in fact forms a reservoir where the particles held in
suspension by the river have time to subside, and its waters to become
pure. The subsidence of course takes place most copiously at the head of
the lake; and here the deposit continues to form new land, adding year
by year to the thousands of acres which it has already left behind it,
and invading more and more the space occupied by the water. Innumerable
plates of mica spangled the fine sand which the river brought down, and
these, mixing with the water, and flashing like minute mirrors as the
sun's rays fell upon them, gave the otherwise muddy stream a silvery
appearance. Had I an opportunity I would make the following
experiments:--
(_a_.) Compare the colour of the light transmitted by a column of the
lake water fifteen feet long with that transmitted by a second column,
of the same length, derived from the melting of freshly fallen mountain
snow.
(_b_.) Compare in the same manner the colour of the ordinary water of
the lake with that of the same water after careful distillation.
(_c_.) Strictly examine whether the light transmitted by the ordinary
water contains an excess of red over that transmitted by the distilled
water: this latter point, as will be seen farther on, is one of peculiar
interest.
The length is fixed at fifteen feet, because I have found this length
extremely efficient in similar experiments.
[Illustration: Fig. 3, 4. Boats' sails inverted by Atmospheric
Refraction.]
[Sidenote: ATMOSPHERIC REFRACTION. 1857.]
On returning to the pier at Villeneuve, a peculiar flickering motion was
manifest upon the surface of the distant portions of the lake, and I
soon noticed that the coast line was inverted by atmospheric refraction.
It required a long distance to produce the effect: no trace of it was
seen about the Castle of Chillon, but at Vevey and beyond it, the whole
coast was clearly inverted; and the houses on the margin of the lake
were also imaged to a certain height. Two boats at a considerable
distance presented the appearance sketched in Figs. 3 and 4; the hull of
each, except a small portion at the end, was invisible, but the sails
seemed lifted up high in the air, with their inverted images below; as
the boats drew nearer the hulls appeared inverted, the apparent height
of the vessel above the surface of the lake being thereby nearly
doubled, while the sails and higher objects, in these cases, were
almost completely cut away. When viewed through a telescope the sensible
horizon of the lake presented a billowy tumultuous appearance, fragments
being incessantly detached from it and suspended in the air.
[Sidenote: MIRAGE. 1857.]
The explanation of this effect is the same as that of the mirage of the
desert, which may be found in almost any book on physics, and which so
tantalized the French soldiers in Egypt. They often mistook this aerial
inversion for the reflection from a lake, and on trial found hot and
sterile sand at the place where they expected refreshing waters. The
effect was shown by Monge, one of the learned men who accompanied the
expedition, to be due to the total reflection of very oblique rays at
the upper surface of the layer of rarefied air which was nearest to the
heated earth. A sandy plain, in the early part of the day, is peculiarly
favourable for the production of such effects; and on the extensive flat
strand which stretches between Mont St. Michel and the coast adjacent to
Avranches in Normandy, I have noticed Mont Tombeline reflected as if
glass instead of sand surrounded it and formed its mirror.
[Sidenote: CHAMOUNI AND THE MONTANVERT. 1857.]
CHAMOUNI AND THE MONTANVERT.
(5.)
On the evening of the 12th of July I reached Chamouni; the weather was
not quite clear, but it was promising; white cumuli had floated round
Mont Blanc during the day, but these diminished more and more, and the
light of the setting sun was of that lingering rosy hue which bodes good
weather. Two parallel beams of a purple tinge were drawn by the shadows
of the adjacent peaks, straight across the Glacier des Bossons, and the
Glacier des Pelerins was also steeped for a time in the same purple
light. Once when the surrounding red illumination was strong, the
shadows of the Grands Mulets falling upon the adjacent snow appeared of
a vivid green.
This green belonged to the class of _subjective_ colours, or colours
produced by contrast, about which a volume might be written. The eye
received the impression of green, but the colour was not external to the
eye. Place a red wafer on white paper, and look at it intently, it will
be surrounded in a little time by a green fringe: move the wafer bodily
away, and the entire space which it occupied upon the paper will appear
green. A body may have its proper colour entirely masked in this way.
Let a red wafer be attached to a piece of red glass, and from a
moderately illuminated position let the sky be regarded through the
glass; the wafer will appear of a vivid green. If a strong beam of light
be sent through a red glass and caused to fall upon a screen, which at
the same time is moderately illuminated by a separate source of white
light, an opaque body placed in the path of the beam will cast a green
shadow upon the screen which may be seen by several hundred persons at
once. If a blue glass be used, the shadow will be yellow, which is the
complementary colour to blue.
[Sidenote: COLOURED SHADOWS. 1857.]
When we suddenly pass from open sunlight to a moderately illuminated
room, it appears dark at first, but after a little time the eye regains
the power of seeing objects distinctly. Thus one effect of light upon
the eye is to render it less sensitive, and light of any particular
colour falling upon the eye blunts its appreciation of that colour. Let
us apply this to the shadow upon the screen. This shadow is moderately
illuminated by a jet of white light; but the space surrounding it is
red, the effect of which upon the eye is to blind it in some degree to
the perception of red. Hence, when the feeble white light of the shadow
reaches the eye, the red component of this light is, as it were,
abstracted from it, and the eye sees the residual colour, which is
green. A similar explanation applies to the shadows of the Grands
Mulets.
On the 13th of July I was joined by my friend Mr. Thomas Hirst, and on
the 14th we examined together the end of the Mer de Glace. In former
times the whole volume of the Arveiron escaped from beneath the ice at
the end of the glacier, forming a fine arch at its place of issue. This
year a fraction only of the water thus found egress; the greater portion
of it escaping laterally from the glacier at the summit of the rocks
called _Les Mottets_, down which it tumbled in a fine cascade. The vault
at the end of the glacier was nevertheless respectable, and rather
tempting to a traveller in search of information regarding the structure
of the ice. Perhaps, however, Nature meant to give me a friendly warning
at the outset, for, while speculating as to the wisdom of entering the
cavern, it suddenly gave way, and, with a crash which rivalled thunder,
the roof strewed itself in ruins upon the floor.
[Sidenote: SUNRISE AT CHAMOUNI. 1857.]
Many years ago I had read with delight Coleridge's poem entitled
'Sunrise in the Valley of Chamouni,' and to witness in all perfection
the scene described by the poet, I waited at Chamouni a day longer than
was otherwise necessary. On the morning of Wednesday, the 15th of July,
I rose before the sun; Mont Blanc and his wondrous staff of Aiguilles
were without a cloud; eastward the sky was of a pale orange which
gradually shaded off to a kind of rosy violet, and this again blended by
imperceptible degrees with the deep zenithal blue. The morning star was
still shining to the right, and the moon also turned a pale face towards
the rising day. The valley was full of music; from the adjacent woods
issued a gush of song, while the sound of the Arve formed a suitable
bass to the shriller melody of the birds. The mountain rose for a time
cold and grand, with no apparent stain upon his snows. Suddenly the
sunbeams struck his crown and converted it into a boss of gold. For some
time it remained the only gilded summit in view, holding communion with
the dawn while all the others waited in silence. These, in the order of
their heights, came afterwards, relaxing, as the sunbeams struck each in
succession, into a blush and smile.
[Sidenote: GLACIER DES BOIS. 1857.]
On the same day we had our luggage transported to the Montanvert, while
we clambered along the lateral moraine of the glacier to the Chapeau.
The rocks alongside the glacier were beautifully scratched and polished,
and I paid particular attention to them, for the purpose of furnishing
myself with a key to ancient glacier action. The scene to my right was
one of the most wonderful I had ever witnessed. Along the entire slope
of the Glacier des Bois, the ice was cleft and riven into the most
striking and fantastic forms. It had not yet suffered much from the
wasting influence of the summer weather, but its towers and minarets
sprang from the general mass with clean chiselled outlines. Some stood
erect, others leaned, while the white debris, strewn here and there over
the glacier, showed where the wintry edifices had fallen, breaking
themselves to pieces, and grinding the masses on which they fell to
powder. Some of them gave way during our inspection of the place, and
shook the valley with the reverberated noise of their fall. I
endeavoured to get near them, but failed; the chasms at the margin of
the glacier were too dangerous, and the stones resting upon the heights
too loosely poised to render persistence in the attempt excusable.
We subsequently crossed the glacier to the Montanvert, and I formally
took up my position there. The rooms of the hotel were separated from
each other by wooden partitions merely, and thus the noise of early
risers in one room was plainly heard in the next. For the sake of quiet,
therefore, I had my bed placed in the _chateau_ next door,--a little
octagonal building erected by some kind and sentimental Frenchman, and
dedicated "_a la Nature_." My host at first demurred, thinking the place
not "_propre_," but I insisted, and he acquiesced. True the stone floor
was dark with moisture, and on the walls a glistening was here and there
observable, which suggested rheumatism, and other penalties, but I had
had no experience of rheumatism, and trusted to the strength which
mountain air and exercise were sure to give me, for power to resist its
attacks. Moreover, to dispel some of the humidity, it was agreed that a
large pine fire should be made there on necessary occasions.
[Sidenote: QUARTERS AT THE MONTANVERT. 1857.]
Though singularly favoured on the whole, still our residence at the
Montanvert was sufficiently long to give us specimens of all kinds of
weather; and thus my chateau derived an interest from the mutations of
external nature. Sometimes no breath disturbed the perfect serenity of
the night, and the moon, set in a black-blue sky, turned a face of
almost supernatural brightness to the mountains, while in her absence
the thick-strewn stars alone flashed and twinkled through the
transparent air. Sometimes dull dank fog choked the valley, and heavy
rain plashed upon the stones outside. On two or three occasions we were
favoured by a thunderstorm, every peal of which broke into a hundred
echoes, while the seams of lightning which ran through the heavens
produced a wonderful intermittence of gloom and glare. And as I sat
within, musing on the experiences of the day, with my pine logs
crackling, and the ruddy fire-light gleaming over the walls, and lending
animation to the visages sketched upon them with charcoal by the guides,
I felt that my position was in every way worthy of a student of nature.
THE MER DE GLACE.
(6.)
[Sidenote: A RIVER OF ICE. 1857.]
The name "Mer de Glace" has doubtless led many who have never seen this
glacier to a totally erroneous conception of its character. Misled
probably by this term, a distinguished writer, for example, defines a
glacier to be a sheet of ice spread out upon the slope of a mountain;
whereas the Mer de Glace is indeed a _river_, and not a _sea_ of ice.
But certain forms upon its surface, often noticed and described, and
which I saw for the first time from the window of our hotel on the
morning of the 16th of July, suggest at once the origin of the name. The
glacier here has the appearance of a sea which, after it had been tossed
by a storm, had suddenly stiffened into rest. The ridges upon its
surface accurately resemble waves in shape, and this singular appearance
is produced in the following way:--
Some distance above the Montanvert--opposite to the Echelets--the
glacier, in passing down an incline, is rent by deep fissures, between
each two of which a ridge of ice intervenes. At first the edges of these
ridges are sharp and angular, but they are soon sculptured off by the
action of the sun. The bearing of the Mer de Glace being approximately
north and south, the sun at mid-day shines down the glacier, or rather
very obliquely across it; and the consequence is, that the fronts of the
ridges, which look downward, remain in shadow all the day, while the
backs of the ridges, which look up the glacier, meet the direct stroke
of the solar rays. The ridges thus acted upon have their hindmost angles
wasted off and converted into slopes which represent the _back_ of a
wave, while the opposite sides of the ridges, which are protected from
the sun, preserve their steepness, and represent the _front_ of the
wave. Fig. 5 will render my meaning at once plain.
[Sidenote: FROZEN WAVES. 1857.]
[Illustration: Fig. 5. Wave-like forms on the Mer de Glace.]
The dotted lines are intended to represent three of the ridges into
which the glacier is divided, with their interposed fissures; the dots
representing the boundaries of the ridges when the glacier is first
broken. The parallel shading lines represent the direction of the sun's
rays, which, falling obliquely upon the ridges, waste away the
right-hand corners, and finally produce wave-like forms.
We spent a day or two in making the general acquaintance of the glacier.
On the 16th we ascended till we came to the rim of the Talefre basin,
from which we had a good view of the glacier system of the region. The
laminated structure of the ice was a point which particularly interested
me; and as I saw the exposed sections of the _neve_, counted the lines
of stratification, and compared these with the lines upon the ends of
the secondary glaciers, I felt the absolute necessity either of
connecting the veined _structure_ with the _strata_ by a continuous
chain of observations, or of proving by ocular evidence that they were
totally distinct from each other. I was well acquainted with the
literature of the subject, but nothing that I had read was sufficient to
prove what I required. Strictly speaking, nothing that had been written
upon the subject rose above the domain of _opinion_, while I felt that
without absolute _demonstration_ the question would never be set at
rest.
[Illustration: Fig. 6. Glacier Table.]
[Sidenote: GLACIER TABLES. 1857.]
On this day we saw some fine glacier tables; flat masses of rock, raised
high upon columns of ice: Fig. 6 is a sketch of one of the finest of
them. Some of them fell from their pedestals while we were near them,
and the clean ice-surfaces which they left behind sparkled with minute
stars as the small bubbles of air ruptured the film of water by which
they were overspread. I also noticed that "petit bruit de crepitation,"
to which M. Agassiz alludes, and which he refers to the rupture of the
ice by the expansion of the air-bubbles contained within it. When I
first read Agassiz's account of it, I thought it might be produced by
the rupture of the minute air-bubbles which incessantly escape from the
glacier. This, doubtless, produces an effect, but there is something in
the character of the sound to be referred, I think, to a less obvious
cause, which I shall notice further on.
[Sidenote: FIRST SIGHT OF THE DIRT-BANDS. 1857.]
At six P.M. this day I reached the Montanvert; and the same evening,
wrapping my plaid around me, I wandered up towards Charmoz, and from its
heights observed, as they had been observed fifteen years previously by
Professor Forbes, the _dirt-bands_ of the Mer de Glace. They were
different from any I had previously seen, and I felt a strong desire to
trace them to their origin. Content, however, with the performance of
the day, and feeling healthily tired by it, I lay down upon the bilberry
bushes and fell asleep. It was dark when I awoke, and I experienced some
difficulty and risk in getting down from the petty eminence referred to.
The illumination of the glacier, as remarked by Professor Forbes, has
great influence upon the appearance of the bands; they are best seen in
a subdued light, and I think for the following reasons:--
The dirt-bands are seen simply because they send less light to the eye
than the cleaner portions of the glacier which lie between them; two
surfaces, differently illuminated, are presented to the eye, and it is
found that this difference is more observable when the light is that of
evening than when it is that of noon.
It is only within certain limits that the eye is able to perceive
differences of intensity in different lights; beyond a certain
intensity, if I may use the expression, light ceases to be light, and
becomes mere pain. The naked eye can detect no difference in brightness
between the electric light and the lime light, although, when we come
to strict measurement, the former may possess many times the intensity
of the latter. It follows from this that we might reduce the ordinary
electric light to a fraction of its intensity, without any perceptible
change of brightness to the naked eye which looks at it. But if we
reduce the lime light in the same proportion the effect would be very
different. This light lies much nearer to the limit at which the eye can
appreciate differences of brightness, and its reduction might bring it
quite within this limit, and make it sensibly dimmer than before. Hence
we see that when two sources of intense light are presented to the eye,
by reducing both the lights in the same proportion, the _difference_
between them may become more perceptible.
[Sidenote: BANDS SEEN BEST BY TWILIGHT. 1857.]
Now the dirt-bands and the spaces between them resemble, in some
measure, the two lights above mentioned. By the full glare of noon both
are so strongly illuminated that the difference which the eye perceives
is very small; as the evening advances the light of both is lowered in
the same proportion, but the differential effect upon the eye is thereby
augmented, and the bands are consequently more clearly seen.
(7.)
On Friday, the 17th of July, we commenced our measurements. Through the
kindness of Sir Roderick Murchison, I found myself in the possession of
an excellent five-inch theodolite, an instrument with the use of which
both my friend Hirst and myself were perfectly familiar. We worked in
concert for a few days to familiarize our assistant with the mode of
proceeding, but afterwards it was my custom to simply determine the
position where a measurement was to be made, and to leave the execution
of it entirely to Mr. Hirst and our guide.
On the 20th of July I made a long excursion up the glacier, examining
the moraines, the crevasses, the structure, the moulins, and the
disintegration of the surface. I was accompanied by a boy named Edouard
Balmat,[A] and found him so good an iceman that I was induced to take
him with me on the following day also.
[Sidenote: THE CLEFT STATION. 1857.]
Looking upwards from the Montanvert to the left of the Aiguille de
Charmoz, a singular gap is observed in the rocky mountain wall, in the
centre of which stands a detached column of granite. Both cleft and
pillar are shown in the frontispiece, to the right. The eminence to the
left of this gap is signalised by Professor Forbes as one of the best
stations from which to view the Mer de Glace, and this point, which I
shall refer to hereafter as the _Cleft Station_, it was now my desire to
attain. From the Montanvert side a steep gully leads to the cleft; up
this couloir we proposed to try the ascent. At a considerable height
above the Mer de Glace, and closely hugging the base of the Aiguille de
Charmoz, is the small Glacier de Tendue, shown in the frontispiece, and
from which a steep slope stretches down to the Mer de Glace. This Tendue
is the most _talkative_ glacier I have ever known; the clatter of the
small stones which fall from it is incessant. Huge masses of granite
also frequently fall upon the glacier from the cliffs above it, and,
being slowly borne downwards by the moving ice, are at length seen
toppling above the terminal face of the glacier. The ice which supports
them being gradually melted, they are at length undermined, and sent
bounding down the slope with peal and rattle, according as the masses
among which they move are large or small. The space beneath the glacier
is cumbered with blocks thus sent down; some of them of enormous size.
[Sidenote: ROUGH ASCENT. 1857.]
The danger arising from this intermittent cannonade, though in reality
small, has caused the guides to swerve from the path which formerly led
across the slope to the promontory of Trelaporte. I say "small,"
because, even should a rock choose the precise moment at which a
traveller is passing to leap down, the boulders at hand are so large and
so capable of bearing a shock that the least presence of mind would be
sufficient to place him in safety. But presence of mind is not to be
calculated on under such circumstances, and hence the guides were right
to abandon the path.
Reaching the mouth of our gully after a rough ascent, we took to the
snow, instead of climbing the adjacent rocks. It was moist and soft, in
fact in a condition altogether favourable for the "regelation" of its
granules. As the foot pressed upon it the particles became cemented
together. A portion of the pressure was transmitted laterally, which
produced attachments beyond the boundary of the foot; thus as the latter
sank, it pressed upon a surface which became continually wider and more
rigid, and at length sufficiently strong to bear the entire weight of
the body; the pressed snow formed in fact a virtual _camel's foot_,
which soon placed a limit to the sinking. It is this same principle of
regelation which enables men to cross snow bridges in safety. By gentle
cautious pressure the loose granules of the substance are cemented into
a continuous mass, all sudden shocks which might cause the frozen
surfaces to snap asunder being avoided. In this way an arch of snow
fifteen or twenty inches in thickness may be rendered so firm that a
man will cross it, although it may span a chasm one hundred feet in
depth.
As we ascended, the incline became very steep, and once or twice we
diverged from the snow to the adjacent rocks; these were disintegrated,
and the slightest disturbance was sufficient to bring them down; some
fell, and from one of them I found it a little difficult to escape; for
it grazed my leg, inflicting a slight wound as it passed. Just before
reaching the cleft at which we aimed, the snow for a short distance was
exceedingly steep, but we surmounted it; and I sat for a time beside the
granite pillar, pleased to find that I could permit my legs to dangle
over a precipice without prejudice to my head.
[Sidenote: CHAMOIS ON THE MOUNTAINS. 1857.]
While we remained here a chamois made its appearance upon the rocks
above us. Deeming itself too near, it climbed higher, and then turned
round to watch us. It was soon joined by a second, and the two formed a
very pretty picture: their attitudes frequently changed, but they were
always graceful; with head erect and horns curved back, a light limb
thrown forward upon a ledge of rock, looking towards us with wild and
earnest gaze, each seemed a type of freedom and agility. Turning now to
the left, we attacked the granite tower, from which we purposed to scan
the glacier, and were soon upon its top. My companion was greatly
pleased--he was "tres-content" to have reached the place--he felt
assured that many old guides would have retreated from that ugly gully,
with its shifting shingle and debris, and his elation reached its climax
in the declaration that, if I resolved to ascend Mont Blanc without a
guide, he was willing to accompany me.
[Sidenote: SCENE FROM THE STATION. 1857.]
From the position which we had attained, the prospect was exceedingly
fine, both of the glaciers and of the mountains. Beside us was the
Aiguille de Charmoz, piercing with its spikes of granite the clear air.
To my mind it is one of the finest of the Aiguilles, noble in mass, with
its summits singularly cleft and splintered. In some atmospheric
colourings it has the exact appearance of a mountain of cast copper, and
the manner in which some of its highest pinnacles are bent, suggesting
the idea of ductility, gives strength to the illusion that the mass is
metallic. At the opposite side of the glacier was the Aiguille Verte,
with a cloud poised upon its point: it has long been the ambition of
climbers to scale this peak, and on this day it was attempted by a young
French count with a long retinue of guides. He had not fair play, for
before we quitted our position we heard the rumble of thunder upon the
mountain, which indicated the presence of a foe more terrible than the
avalanches themselves. Higher to the right, and also at the opposite
side of the glacier, rose the Aiguille du Moine; and beyond was the
basin of the Talefre, the ice cascade issuing from which appeared, from
our position, like the foam of a waterfall. Then came the Aiguille de
Lechaud, the Petite Jorasse, the Grande Jorasse, and the Mont Tacul; all
of which form a cradle for the Glacier de Lechaud. Mont Mallet, the
Periades, and the Aiguille Noire, came next, and then the singular
obelisk of the Aiguille du Geant, from which a serrated edge of cliff
descends to the summit of the "Col."
[Sidenote: SERACS OF THE COL DU GEANT. 1857.]
Over the slopes of the Col du Geant was spread a coverlet of shining
snow, at some places apparently as smooth as polished marble, at others
broken so as to form precipices, on the pale blue faces of which the
horizontal lines of bedding were beautifully drawn. As the eye
approaches the line which stretches from the Rognon to the Aiguille
Noire, the repose of the _neve_ becomes more and more disturbed. Vast
chasms are formed, which however are still merely indicative of the
trouble in advance. If the glacier were lifted off we should probably
see that the line just referred to would lie along the summit of a
steep gorge; over this summit the glacier is pushed, and has its back
periodically broken, thus forming vast transverse ridges which follow
each other in succession down the slope. At the summit these ridges are
often cleft by fissures transverse to them, thus forming detached towers
of ice of the most picturesque and imposing character.[B] These towers
often fall; and while some are caught upon the platforms of the cascade,
others struggle with the slow energy of a behemoth through the debris
which opposes them, reach the edges of the precipices which rise in
succession along the fall, leap over, and, amid ice-smoke and
thunder-peals, fight their way downwards.
[Sidenote: GLACIER MOTION. 1857.]
A great number of secondary glaciers were in sight hanging on the steep
slopes of the mountains, and from them streams sped downwards, falling
over the rocks, and filling the valley with a low rich music. In front
of me, for example, was the Glacier du Moine, and I could not help
feeling as I looked at it, that the arguments drawn from the deportment
of such glaciers against the "sliding theory," and which are still
repeated in works upon the Alps, militate just as strongly against the
"viscous theory." "How," demands the antagonist of the sliding theory,
"can a secondary glacier exist upon so steep a slope? why does it not
slide down as an avalanche?" "But how," the person addressed may retort,
"can a mass which you assume to be viscous exist under similar
conditions? If it be viscous, what prevents it from rolling down?" The
sliding theory assumes the lubrication of the bed of the glacier, but on
this cold height the quantity melted is too small to lubricate the bed,
and hence the slow motion of these glaciers. Thus a sliding-theory man
might reason, and, if the external deportment of secondary glaciers were
to decide the question, De Saussure might perhaps have the best of the
argument.
And with regard to the current idea, originated by M. de Charpentier,
and adopted by Professor Forbes, that if a glacier slides it must slide
as an avalanche, it may be simply retorted that, in part, _it does so_;
but if it be asserted that an _accelerated motion_ is the necessary
motion of an avalanche, the statement needs qualification. An avalanche
on passing through a rough couloir soon attains a uniform velocity--its
motion being accelerated only up to the point when the sum of the
resistances acting upon it is equal to the force drawing it downwards.
These resistances are furnished by the numberless asperities which the
mass encounters, and which incessantly check its descent, and render an
accumulation of motion impossible. The motion of a man walking down
stairs may be on the whole uniform, but it is really made up of an
aggregate of small motions, each of which is accelerated; and it is easy
to conceive how a glacier moving over an uneven bed, when released from
one opposing obstacle will be checked by another, and its motion thus
rendered sensibly uniform.
[Sidenote: MORAINES. 1857.]
[Sidenote: TRIBUTARIES OF THE MER DE GLACE. 1857.]
[Illustration: Fig. 7. Tributaries of the Mer de Glace.]
From the Aiguille du Geant and Les Periades a glacier descended, which
was separated by the promontory of La Noire from the glacier proceeding
from the Col du Geant. A small moraine was formed between them, which is
marked _a_ upon the diagram, Fig. 7. The great mass of the glacier
descending from the Col du Geant came next, and this was bounded on the
side nearest to Trelaporte by a small moraine _b_, the origin of which I
could not see, its upper portion being shut out by a mountain
promontory. Between the moraine _b_ and the actual side of the valley
was another little glacier, derived from some of the lateral
tributaries. It was, however, between the moraines _a_ and _b_ that the
great mass of the Glacier du Geant really lay. At the promontory of the
Tacul the lateral moraines of the Glacier des Periades and of the
Glacier de Lechaud united to form the medial moraine _c_ of the Mer de
Glace. Carrying the eye across the Lechaud, we had the moraine _d_
formed by the union of the lateral moraines of the Lechaud and Talefre;
further to the left was the moraine _e_, which came from the Jardin, and
beyond it was the second lateral moraine of the Talefre. The Mer de
Glace is formed by the confluence of the whole of the glaciers here
named; being forced at Trelaporte through a passage, the width of which
appears considerably less than that of the single tributary, the Glacier
du Geant.
In the ice near Trelaporte the blue veins of the glacier are beautifully
shown; but they vary in distinctness according to the manner in which
they are looked at. When regarded obliquely their colour is not so
pronounced as when the vision plunges deeply into them. The weathered
ice of the surface near Trelaporte could be cloven with great facility;
I could with ease obtain plates of it a quarter of an inch thick, and
possessing two square feet of surface. On the 28th of July I followed
the veins several times from side to side across the Geant portion of
the Mer de Glace; starting from one side, and walking along the veins,
my route was directed obliquely downwards towards the axis of the
tributary. At the axis I was forced to turn, in order to keep along the
veins, and now ascended along a line which formed nearly the same angle
with the axis at the other side. Thus the veins led me as it were along
the two sides of a triangle, the vertex of which was near the centre of
the glacier. The vertex was, however, in reality rounded off, and the
figure rather resembled a hyperbola, which tended to coincidence with
its asymptotes. This observation corroborates those of Professor Forbes
with regard to the position of the veins, and, like him, I found that at
the centre the veining, whose normal direction would be transverse to
the glacier, was contorted and confused.
[Sidenote: WASTING OF ICE. 1857.]
Near the side of the Glacier du Geant, above the promontory of
Trelaporte, the ice is rent in a remarkable manner. Looking upwards from
the lower portions of the glacier, a series of vertical walls, rising
apparently one above the other, face the observer. I clambered up among
these singular terraces, and now recognise, both from my sketch and
memory, that their peculiar forms are due to the same action as that
which has given their shape to the "billows" of the Mer de Glace. A
series of profound crevasses is first formed. The Glacier du Geant
deviates 14 deg. from the meridian line, and hence the sun shines nearly
down it during the middle portion of each day. The backs of the ridges
between the crevasses are thus rounded off, one boundary of each fissure
is destroyed, or at least becomes a mere steep declivity, while the
other boundary being shaded from the sun preserves its verticality; and
thus a very curious series of precipices is formed.
Through all this dislocation, the little moraine on which I have placed
the letter _b_ in the sketch maintains its right to existence, and under
it the laminated structure of this portion of the glacier appears to
reach its most perfect development. The moraine was generally a mere
dirt track, but one or two immense blocks of granite were perched upon
it. I examined the ice underneath one of these, being desirous of seeing
whether the pressure resulting from its enormous weight would produce a
veining, but the result was not satisfactory. Veins were certainly to be
seen in directions different from the normal ones, but whether they were
due to the bending of the latter, or were directly owing to the pressure
of the block, I could not say. The sides of a stream which had cut a
deep gorge in the clean ice of the Glacier du Geant afforded a fine
opportunity of observing the structure. It was very remarkable--highly
significant indeed in a theoretic point of view. Two long and
remarkably deep blue veins traversed the bottom of the stream, and
bending upwards at a place where the rivulet curved, drew themselves
like a pair of parallel lines upon the clean white ice. But the general
structure was of a totally different character; it did not consist of
long bars, but approximated to the lenticular form, and was, moreover,
of a washy paleness, which scarcely exceeded in depth of colouring the
whitish ice around.
[Sidenote: GROOVES ON THE SURFACE. 1857.]
To the investigator of the structure nothing can be finer than the
appearance of the glacier from one of the ice terraces cut in the
Glacier du Geant by its passage round Trelaporte. As far as the vision
extended the dirt upon the surface of the ice was arranged in striae.
These striae were not always straight lines, nor were they unbroken
curves. Within slight limits the various parts into which a glacier is
cut up by its crevasses enjoy a kind of independent motion. The grooves,
for example, on two ridges which have been separated by a small fissure,
may one day have their striae perfect continuations of each other, but in
a short time this identity of direction may be destroyed by a difference
of motion between the ridges. Thus it is that the grooves upon the
surface above Trelaporte are bent hither and thither, a crack or seam
always marking the point where their continuity is ruptured. This
bending occurs, however, within limits sufficiently small to enable the
striae to preserve the same general direction.
[Sidenote: SEAMS OF WHITE ICE. 1857.]