before us up to the Æggischhorn and Märgelin See is the long last
reach of the Aletsch, with its great medial moraine running along its
back. At hand is the wild gorge of the Massa, in which the snout of
the glacier lies couched like the head of a serpent. The beautiful
system of the Oberaletsch glaciers is within easy reach. Above us
is a peak called the Sparrenhorn, accessible to the most moderate
climber, and on the summit of which little more than an hour's
exertion will place you and me. Below us now is the Oberaletsch
glacier, exhibiting the most perfect of medial moraines. Near us
is the great mass of the Aletschhorn, clasped by its névés, and
culminating in brown rock. It is supported by other peaks almost as
noble as itself. The Nesthorn is at hand; while sweeping round to the
west we strike the glorious triad already referred to, the Weisshorn,
the Matterhorn, and the Dom. Take one glance at the crevasses of the
glacier immediately below us. It tumbles at its end down a steep
incline, and is greatly riven. But the crevasses open before the
steep part is reached, and you notice the coalescence of marginal and
transverse crevasses, producing a system of curved fissures with the
convexities of the curves pointing upwards. The mechanical reason of
this is now known to you. The glacier-tables are also numerous and
fine. I should like to linger with you here for a week, exploring the
existing glaciers, and tracing out the evidences of others that have
passed away.
§ 52. _The Riffelberg and Görner Glacier._
354. And though our measurements and observations on the Mer de Glace
are more or less representative of all that can be made or solved
elsewhere, I am unwilling to leave you unacquainted with the great
system of glaciers which stream from the northern slopes of Monte
Rosa and the adjacent mountains. From the Bel Alp we can descend to
Brieg, and thence drive to Visp; but you and I prefer the breezy
heights, so we sweep round the promontory of the Nessel, until we
stand over the Rhone valley, in front of Visp. From this village an
hour's walking carries us to Stalden, where the valley divides into
two branches: the one leading through Saas over the Monte Moro, and
the other through St. Nicholas to Zermatt. The latter is our route.
355. We reach Zermatt, but do not halt here. On the mountain ridge,
4,000 feet above the valley, we discern the Riffelberg hotel. This
we reach. Right in front of us is the pinnacle of the Matterhorn,
upon the top of which it must appear incredible to you that a human
foot could ever tread. Constancy and skill, however, accomplished
this, but in the first instance at a terrible price. In the little
churchyard of Zermatt we have seen the graves of two of the greatest
mountaineers that Savoy and England have produced: and who, with two
gallant young companions, fell from the Matterhorn in 1865.
356. At the Riffelberg we are within an hour's walk of the famous
Görner Grat, which commands so grand a view of the glaciers of Monte
Rosa. But yonder huge knob of perfectly bare rock, which is called
the Riffelhorn, must be our station. What the Cleft Station is to
the Mer de Glace, the Riffelhorn is to the Görner glacier and its
tributaries. From its lower side the rock, easy as it may seem, is
inaccessible. Here, indeed, in 1865, a fifth good man met his end,
and he also lies beside his fellow countrymen in the churchyard of
Zermatt. Passing a little tarn, or lake, called the Riffel See, we
assail the Riffelhorn on its upper side. It is capital rock-practice
to reach the summit; and from it we command a most extraordinary
scene.
357. The huge and many-peaked mass of Monte Rosa faces us, and we
scan its snows from bottom to top. To the right is the mighty ridge
of the Lyskamm, also laden with snow; and between both lies the
Western Glacier of Monte Rosa. This glacier meets another from the
vast snow-fields of the Cima di Jazzi; they join to form the Görner
glacier, and from their place of junction stretches the customary
medial moraine. On this side of the Lyskamm rise two beautifully
snowy eminences, the Twins Castor and Pollux; then come the brown
crags of the Breithorn, then the Little Matterhorn, and then the
broad snow-field of the Théodule, out of which springs the Great
Matterhorn, and which you and I will cross subsequently into Italy.
358. The valleys and depressions between these mountains are filled
with glaciers. Down the flanks of the Twin Castor comes the Glacier
des Jumeaux, from Pollux comes the Schwartze glacier, from the
Breithorn the Trifti glacier, then come the Little Matterhorn glacier
and the Théodule glacier, each, as it welds itself to the trunk,
carrying with it its medial moraine. We can count nine such moraines
from our present position. And to a still more surprising degree
than on the Mer de Glace, we notice the power of the ice to yield to
pressure; the broad névés being squeezed on the trunk of the Görner
into white stripes, which become ever narrower between the bounding
moraines, and finally disappear under their own shingle.
[Illustration: THE GÖRNER GLACIER, WITH MONTE ROSA IN THE DISTANCE,
AND THE RIFFELHORN TO THE LEFT.]
359. On the two main tributaries we also notice moraines which seem
in each case to rise from the body of the glacier, appearing in the
middle of the ice without any apparent origin higher up. These at
their sources, are sub-glacial moraines, which have been rubbed away
from rocky promontories entirely covered with ice. They lie hidden
for a time in the body of the glacier, and appear at the surface
where the ice above them has been melted away by the sun.
360. This is the place to mention a notion long entertained by the
inhabitants of the high Alps, that glaciers possess the power of
thrusting out all impurities from them. On the Mer de Glace you and
I have noticed large patches of clay and black mud which evidently
came from the body of the glacier, and we can therefore understand
how natural was this notion of extrusion to people unaccustomed to
close observation. But the power of the glacier in this respect is
in reality the power of the sun, which fuses the ice above concealed
impurities, and, like the bodies of the guides on the Glacier des
Bossons (143), brings them to the light of day.
361. On no other glacier will you find more objects of interest than
on the Görner. Sand-cones, glacier-tables, deep ice-gorges cut by
streams and bridged fantastically by boulders, moulins, sometimes
arched ice-caverns of extraordinary size and beauty. On the lower
part of the glacier we notice the partial disappearance of the medial
moraine in the crevasses, and its reappearance at the foot of the
incline. For many years this glacier was steadily advancing on the
meadow in front of it, ploughing up the soil and overturning the
chalets in its way. It now shares in the general retreat exhibited
during the last fifteen years among the glaciers of the Alps. As
usual, a river, the Visp, rushes from a vault at the extremity of the
Görner glacier.
§ 53. _Ancient Glaciers of Switzerland._
362. You have not lost the memory of the old Moraine, which
interested us so much in our first ascent from the source of the
Arveiron; for it opened our minds to the fact that at one period of
its history the Mer de Glace attained far greater dimensions than it
now exhibits. Our experience since that time has enabled us to pursue
these evidences of ice action to an extent of which we had then no
notion.
363. Close to the existing glacier, for example, we have repeatedly
seen the mountain side laid bare by the retreat of the ice. This is
especially conspicuous just now, because for the last fifteen or
sixteen years the glaciers of the Alps have been steadily shrinking;
so that it is no uncommon thing to see the marginal rocks laid bare
for a height of fifty, sixty, eighty, or even one hundred feet above
the present glacier. On the rocks thus exposed we see the evident
marks of the sliding; and our eyes and minds have been so educated in
the observation of these appearances that we are now able to detect,
with certainty, icemarks, or moraines, ancient or modern, wherever
they appear.
364. But the elevations at which we have found such evidence might
well shake belief in the conclusions to which they point. Beside
the Massa Gorge, at 1,000 feet above the present Aletsch, we found
a great old moraine. Descending the meadows between the Bel Alp
and Flatten, we found another, now clothed with grass, and bearing
a village on its back. But I wish to carry you to a region which
exhibits these evidences on a still grander and more impressive
scale. We have already taken a brief flight to the valley of
Hasli and the Glacier of the Aar. Let us make that glacier our
starting-point. Walking from it downwards towards the Grimsel, we
pass everywhere over rocks singularly rounded, and fluted, and
scarred. These appearances are manifestly the work of the glacier in
recent times. But we approach the Grimsel, and at the turning of the
valley stand before the precipitous granite flank of the mountain.
The traces of the ancient ice are here as plain as they are amazing.
The rocks are so hard that not only the fluting and polishing, but
even the fine scratches which date back unnamable thousands of years
are as evident as if they had been made yesterday. We may trace these
evidences to a height of two thousand feet above the present valley
bed. It is indubitable that an ice-river of this astounding depth
once flowed through the vale of Hasli.
365. Yonder is the summit of the Siedelhorn; and if we gain it, the
Unteraar glacier will lie like a map below us. From this commanding
point we plainly see marked upon the mountain sides the height to
which the ancient ice extended. The ice-ground part of the mountains
is clearly distinguished from the splintered crests which in those
distant days rose above the surface of the glacier, and which must
have then appeared as island peaks and crests in the midst of an
ocean of ice.
366. We now scamper down the Siedelhorn, get once more into the
valley of Hasli, along which we follow for more than twenty miles
the traces of the ice. Fluted precipices, polished slabs, and
beautifully-rounded granite domes. Right and left upon the mountain
flanks, at great elevations, the evidences appear. We follow the
footsteps of the glacier to the Lake of Brientz; and if we prolonged
our enquiries, we should learn that all the lake beds of this region,
at the time now referred to, bore the burden of immense masses of ice.
367. Instead of the vale of Hasli, we might take the valley of the
Rhone. The traces of a mighty glacier, which formerly filled it,
may be followed all the way to Martigny, which is 60 miles distant
from the present ice. At Martigny the Rhone glacier was reinforced
by another from Mont Blanc, and the welded masses moved onward,
planing the mountains right and left, to the Lake of Geneva, the
basin of which they entirely filled. Other evidences prove that the
glacier did not end here, but pushed across the low country until it
encountered the limestone barrier of the Jura Mountains.
§ 54. _Erratic Blocks._
368. What are these other evidences? We have seen mighty rocks poised
on the moraines of the Mer de Glace, and we now know that, unless
they are split and shattered by the frost, these rocks will, at
some distant day, be landed bodily by the Glacier des Bois in the
valley of Chamouni. You have already learned that these boulders
often reveal the mineralogical nature of the mountains among which
the glacier has passed; that specimens are thus brought down of a
character totally different from the rocks among which they are
finally landed; this is strikingly the case with the _erratic blocks_
stranded along the Jura.
369. For the Jura itself, as already stated, is limestone; there is
no trace of native granite to be found amongst these hills. Still
along the breast of the mountain above the town of Neufchâtel, and at
about 800 feet above the lake of Neufchâtel, we find stranded a belt
of granite boulders from Mont Blanc. And when we clear the soil away
from the adjacent mountain side, we find upon the limestone rocks the
scarrings of the ancient glacier which brought the boulders here.
370. The most famous of these rocks, called the Pierre à Bôt,
measures 50 feet in length, 40 in height, and 20 in width.
Multiplying these three numbers together, we obtain 40,000 cubic feet
as the volume of the boulder.
371. But this is small compared with some of the rocks which
constitute the freight of even recent glaciers. Let us visit another
of them. We have already been to Stalden, where the valley divides
into two branches, the right branch running to St. Nicholas and
Zermatt, and the left one to Saas and the Monte Moro. Three hours
above Saas we come upon the end of the Allelein glacier, not filling
the main valley, but thrown athwart it so as to stop its drainage
like a dam. Above this ice-dam we have the Mattmark Lake, and at the
head of the lake a small inn well known to travellers over the Monte
Moro.
372. Close to this inn is the greatest boulder that we have ever
seen. It measures 240,000 cubic feet. Looking across the valley we
notice a glacier with its present end half a mile from the boulder.
The stone, I believe, is serpentine, and were you and I to explore
the Schwartzberg glacier to its upper fastnesses, we should find
among them the birthplace of this gigantic stone. Four-and-twenty
years ago, when the glacier reached the place now occupied by the
boulder, it landed there its mighty freight, and then retreated.
There is a second ice-borne rock at hand which would be considered
vast were it not dwarfed by the aspect of its huger neighbour.
373. Evidence of this kind might be multiplied to any extent. In
fact, at this moment, distinguished men, like Professor Favre of
Geneva, are determining from the distribution of the erratic blocks
the extent of the ancient glaciers of Switzerland. It was, however,
an engineer named Venetz that first brought these evidences to light,
and announced to an incredulous world the vast extension of the
ancient ice. M. Agassiz afterwards developed and wonderfully expanded
the discovery. Perhaps the most interesting observation regarding
ancient glaciers is that of Dr. Hooker, who, during a recent visit
to Palestine, found the celebrated Cedars of Lebanon growing upon
ancient moraines.
§ 55. _Ancient Glaciers of England, Ireland, Scotland, and Wales._
374. At the time the ice attained this extraordinary development in
the Alps, many other portions of Europe, where no glaciers now exist,
were covered with them. In the Highlands of Scotland, among the
mountains of England, Ireland, and Wales, the ancient glaciers have
written their story as plainly as in the Alps themselves. I should
like to wander with you through Borrodale in Cumberland, or through
the valleys near Bethgellert in Wales. Under all the beauty of the
present scenery we should discover the memorials of a time when the
whole region was locked in the embrace of ice. Professor Ramsay is
especially distinguished by his writings on the ancient glaciers of
Wales.
375. We have made the acquaintance of the Reeks of Magillicuddy as
the great condensers of Atlantic vapour. At the time now referred to,
this moisture did not fall as soft and fructifying rain, but as snow,
which formed the nutriment of great glaciers. A chain of lakes now
constitutes the chief attraction of Killarney, the Lower, the Middle,
and the Upper Lake. Let us suppose ourselves rowing towards the head
of the Upper Lake with the Purple Mountain to our left. Remembering
our travels in the Alps, you would infallibly call my attention to
the planing of the rocks, and declare the action to be unmistakably
that of glaciers. With our attention thus sharpened, we land at
the head of the lake, and walk up the Black Valley to the base of
Magillicuddy's Reeks. Your conclusion would be, that this valley
tells a tale as wonderful as that of Hasli.
376. We reach our boat and row homewards along the Upper Lake. Its
islands now possess a new interest for us. Some of them are bare,
others are covered wholly or in part with luxuriant vegetation; but
both the naked and clothed islands are glaciated. The weathering of
ages has not altered their forms: there are the Cannon Rock, the
Giant's Coffin, the Man of War, all sculptured as if the chisel had
passed over them in our own lifetime. These lakes, now fringed with
tender woodland beauty, were all occupied by the ancient ice. It has
disappeared, and seeds from other regions have been wafted thither
to sow the trees, the shrubs, the ferns, and the grasses which now
beautify Killarney. Man himself, they say, has made his appearance in
the world since that time of ice; but of the real period and manner
of man's introduction little is professed to be known since, to make
them square with science, new meanings have been found for the
beautiful myths and stories of the Bible.
377. It is the nature and tendency of the human mind to look backward
and forward; to endeavour to restore the past and predict the future.
Thus endowed, from data patiently and painfully won, we recover in
idea a state of things which existed thousands, it may be millions,
of years before the history of the human race began.
§ 56. _The Glacial Epoch._
378. This period of ice-extension has been named the _Glacial Epoch_.
In accounting for it great minds have fallen into grave errors, as we
shall presently see.
379. The substance on which we have thus far been working exists in
three different states: as a solid in ice; as a liquid in water; as
a gas in vapour. To cause it to pass from one of these states to the
next following one, _heat_ is necessary.
380. Dig a hole in the ice of the Mer de Glace in summer, and place
a thermometer in the hole; it will stand at 32° Fahr. Dip your
thermometer into one of the glacier streams; it will still mark 32°.
_The water is therefore as cold as ice._
381. Hence the whole of the heat poured by the sun upon the glacier,
and which has been absorbed by the glacier, is expended in simply
liquefying the ice, and not in rendering either ice or water a single
degree warmer.
382. Expose water to a fire; it becomes hotter for a time. It boils,
and from that moment it ceases to get hotter. After it has begun to
boil, all the heat communicated by the fire is carried away by the
steam, _though the steam itself is not the least fraction of a degree
hotter than the water_.
383. In fact, simply to liquefy ice a large quantity of heat
is necessary, and to vaporize water a still larger quantity is
necessary. And inasmuch as this heat does not render the water warmer
than the ice, nor the steam warmer than the water, it was at one time
supposed to be _hidden_ in the water and in the steam. And it was
therefore called _latent_ heat.
384. Let us ask how much heat must the sun expend in order to convert
a pound weight of the tropical ocean into vapour? This problem has
been accurately solved by experiment. It would require in round
numbers 1,000 times the amount of heat necessary to raise one pound
of water one degree in temperature.
385. But the quantity of heat which would raise the temperature of a
pound of water one degree would raise the temperature of a pound of
iron _ten_ degrees. This has been also proved by experiment. Hence
to convert one pound of the tropical ocean into vapour the sun must
expend 10,000 times as much heat as would raise one pound of iron one
degree in temperature.
386. This quantity of heat would raise the temperature of 5 lbs. of
iron 2,000 degrees, which is the fusing point of cast iron; at this
temperature the metal would not only be _white hot_, but would be
passing into the molten condition.
387. Consider the conclusions at which we have now arrived. For every
pound of tropical vapour, or for every pound of Alpine ice produced
by the congelation of that vapour, an amount of heat has been
expended by the sun sufficient to raise 5 lbs. of cast iron to its
melting-point.
388. It would not be difficult to calculate approximately the weight
of the Mer de Glace and its tributaries--to say, for example, that
they contained so many millions of millions of tons of ice and snow.
Let the place of the ice be taken by a mass of white-hot iron of
quintuple the weight; with such a picture before your mind you get
some notion of the enormous amount of heat paid out by the sun to
produce the present glacier.
389. You must think over this, until it is as clear as sunshine.
For you must never henceforth fall into the error already referred
to, and which has entangled so many. So natural was the association
of ice and cold, that even celebrated men assumed that all that is
needed to produce a great extension of our glaciers is a diminution
of the sun's temperature. Had they gone through the foregoing
reflections and calculations, they would probably have demanded more
heat instead of less for the production of a "glacial epoch." What
they really needed were _condensers_ sufficiently powerful to congeal
the vapour generated by the heat of the sun.
§ 57. _Glacier Theories._
390. You have not forgotten, and hardly ever can forget, our climbs
to the Cleft Station. Thoughts were then suggested which we have not
yet discussed. We saw the branch glaciers coming down from their
névés, welding themselves together, pushing through Trélaporte, and
afterwards moving through the sinuous valley of the Mer de Glace.
These appearances alone, without taking into account subsequent
observations, were sufficient to suggest the idea that glacier
ice, however hard and brittle it may appear, is really a viscous
substance, resembling treacle, or honey, or tar, or lava.
§ 58. _Dilatation and Sliding Theories._
391. Still this was not the notion expressed by the majority of
writers upon glaciers. Scheuchzer of Zürich, a great naturalist,
visited the glaciers in 1705, and propounded a theory of their
motion. Water, he knew, expands in freezing, and the force of
expansion is so great, that thick bombshells filled with water, and
permitted to freeze, are, as we know (312), shattered to pieces by
the ice within. Scheuchzer supposed that the water in the fissures of
the glaciers, freezing there and expanding with resistless force, was
the power which urged the glacier downwards. He added to this theory
other notions of a less scientific kind.
392. Many years subsequently, De Charpentier of Bex renewed and
developed this theory with such ability and completeness, that it was
long known as Charpentier's Theory of Dilatation. M. Agassiz for a
time espoused this theory, and it was also more or less distinctly
held by other writers. The glacier, in fact, was considered to be a
magazine of cold, capable of freezing all water percolating through
it. The theory was abandoned when this notion of glacier cold was
proved by M. Agassiz to be untenable.
393. In 1760, Altmann and Grüner propounded the view that glaciers
moved by sliding over their beds. Nearly forty years subsequently,
this notion was revived by De Saussure, and it has therefore been
called "De Saussure's Theory," or the "Sliding Theory" of glacier
motion.
394. There was, however, but little reason to connect the name of
De Saussure with this or any other theory of glaciers. Incessantly
occupied in observations of another kind, this celebrated man devoted
very little time or thought to the question of glacier motion. What
he has written upon the subject reads less like the elaboration of a
theory than the expression of an opinion.
§ 59. _Plastic Theory._
395. By none of these writers is the property of viscosity or
plasticity ascribed to glacier ice; the appearances of many glaciers
are, however, so suggestive of this idea that we may be sure it
would have found more frequent expression, were it not in such
apparent contradiction with our every-day experience of ice.
396. Still the idea found its advocates. In a little book, published
in 1773, and entitled "Picturesque Journey to the Glaciers of Savoy,"
Bordier of Geneva wrote thus:--"It is now time to look at all these
objects with the eyes of reason; to study, in the first place, the
position and the progression of glaciers, and to seek the solution of
their principal phenomena. At the first aspect of the ice-mountains
an observation presents itself, which appears sufficient to explain
all. It is that the entire mass of ice is connected together, and
presses from above downwards after the manner of fluids. Let us then
regard the ice, not as a mass entirely rigid and immobile, but as a
heap of coagulated matter, or as softened wax, flexible and ductile
to a certain point."[F] Here probably for the first time the quality
of plasticity is ascribed to the ice of glaciers.
[F] I am indebted to my distinguished friend Prof. Studer of Berne
for directing my attention to Bordier's book, and to my friends at
the British Museum for the great trouble they have taken to find it
for me.