Atlantic Monthly, Volume 12, No. 73, November, 1863 by Various

V >> Various >> Atlantic Monthly, Volume 12, No. 73, November, 1863

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Ice of this kind, resulting from the direct congelation of water, is
easily recognized under all circumstances by its regular
stratification, the alternate beds varying in thickness according to the
intensity of the cold, and its continuance below the freezing-point
during a longer or shorter period. Singly, these layers consist of
irregular crystals confusedly blended together, as in large masses of
crystalline rocks in which a crystalline structure prevails, though
regular crystals occur but rarely. The appearance of stratification is
the result of the circumstances under which the water congeals. The
temperature varies much more rapidly in the atmosphere around the earth
than in the waters upon its surface. When the atmosphere above any sheet
of water sinks below the freezing-point, there stretches over its
surface a stratum of cold air, determining by its intensity and duration
the formation of the first stratum of ice. According to the alternations
of temperature, this process goes on with varying activity until the
sheet of ice is so thick that it becomes itself a shelter to the water
below, and protects it, to a certain degree, from the cold without. Thus
a given thickness of ice may cause a suspension of the freezing process,
and the first ice-stratum may even be partially thawed before the cold
is renewed with such intensity as to continue the thickening of the
ice-sheet by the addition of fresh layers. The strata or beds of ice
increase gradually in this manner, their separation being rendered still
more distinct by the accumulation of air-bubbles, which, during a hot
and clear day, may rise from a muddy bottom in great numbers. In
consequence of these occasional collections of air-bubbles, the layers
differ, not only in density and closeness, but also in color, the more
compact strata being blue and transparent, while those containing a
greater quantity of air-bubbles are opaque and whitish, like water
beaten to froth.

A cake of pond-ice, such as is daily left in summer at our doors, if
held against the light and turned in different directions, will exhibit
all these phenomena very distinctly, and we may learn still more of its
structure by watching its gradual melting. The process of decomposition
is as different in fresh-water ice and in land-or glacier-ice and that
of their formation. Pond-ice, in contact with warm air, melts uniformly
over its whole surface, the mass being thus gradually reduces from the
exterior till it vanishes completely. If the process be slow, the
temperature of the air-bubbles contained in it may be so raised as to
form the vertical funnels or tubes alluded to above. By the anastomosing
of these funnels, the whole mass may be reduced to a collection of
angular pyramids, more or less closely united by cross-beams of ice, and
it finally falls to pieces when the spaces in the interior have become
for numerous as to render it completely cavernous. Such a breaking-up of
ice is always caused by the enlargement of the open spaces produces by
the elevated temperature of the air-bubbles, these spaces being
necessarily more or less parallel with one another, and vertical in
their position, owing to the natural tendency of the air-bubbles to work
their way upward till they reach the surface, where they escape. A sheet
of ice, of this kind, floating upon water, dissolves in the same manner,
melting wholly from the surface, if the process be sufficiently rapid,
or falling to pieces, if the air-bubbles are gradually raised in their
temperature sufficiently to render the whole mass cavernous and
incoherent. If we now compare these facts with what is known of the
structure of land-ice, we shall see that the mode of formation in the
two cases differs essentially.

Land-ice, of which both the ice-fields of the Arctics and glaciers
consist, is produced by the slow and gradual transformation of snow into
ice; and though the ice thus formed may eventually be as clear and
transparent as the purest pond- or river-ice, its structure is
nevertheless entirely distinct. We may trace these different processes
during any moderately cold winter in the ponds and snow-meadows
immediately about us. We need not join an Arctic exploring expedition,
nor even undertake a more tempting trip to the Alps, in order to
investigate these phenomena for ourselves, if we have any curiosity to
do so. The first warm day after a thick fall of light, dry snow, such as
occurs in the coldest of our winter weather, is sufficient to melt its
surface. As this snow is porous, the water readily penetrates it, having
also a tendency to sink by its own weight, so that the whole mass
becomes more or less filled with moisture in the course of the day.
Daring the lower temperature of the night, however, the water is frozen
again, and the snow is now filled with new ice-particles. Let this
process be continued long enough, and the mass of snow is changed to a
kind of ice-gravel, or, if the grains adhere together, to something like
what we call pudding-stone, allowing, of course, for the difference of
material; the snow, which has been rendered cohesive by the process of
partial melting and regelation, holding the ice-globules together, just
as the loose materials of the pudding-stone are held together by the
cement which unites them.

Within this mass, air is intercepted and held inclosed between the
particles of ice. The process by which snow-flakes or snow-crystals are
transformed into grains of ice, more or less compact, is easily
understood. It is the result of a partial thawing, under a temperature
maintained very nearly at thirty-two degrees, falling sometimes a little
below, and then rising a little above the freezing-point, and thus
producing constant alternations of freezing and thawing in the same mass
of snow. This process amounts to a kind of kneading of the snow, and
when combined with the cohesion among the particles more closely held
together in one snow-flake, it produces granular ice. Of course, the
change takes place gradually, and is unequal in its progress at
different depths in the same bed of recently fallen snow. It depends
greatly on the amount of moisture infiltrating the mass, whether derived
from the melting of its own surface, or from the accumulation of dew or
the falling of rain or mist upon it. The amount of water retained within
the mass will also be greatly affected by the bottom on which it rests
and by the state of the atmosphere. Under a certain temperature, the
snow may only be glazed at the surface by the formation of a thin, icy
crust, an outer membrane, as it were, protecting the mass below from a
deeper transformation into ice; or it may be rapidly soaked throughout
its whole bulk, the snow being thus changed into a kind of soft pulp,
what we commonly call slosh, which, upon freezing, becomes at once
compact ice; or, the water sinking rapidly, the lower layers only may be
soaked, while the upper portion remains comparatively dry. But, under
all these various circumstances, frost will transform the crystalline
snow into more or less compact ice, the mass of which will be composed
of an infinite number of aggregated snow-particles, very unequal in
regularity of outline, and cemented by ice of another kind, derived from
the freezing of the infiltrated moisture, the whole being interspersed
with air. Let the temperature rise, and such a mass, rigid before, will
resolve itself again into disconnected ice-particles, like grains more
or less rounded. The process may be repeated till the whole mass is
transformed into very compact, almost uniformly transparent and blue
ice, broken only by the intervening air-bubbles. Such a mass of ice,
when exposed to a temperature sufficiently high to dissolve it, does not
melt from the surface and disappear by a gradual diminution of its bulk,
like pond-ice, but crumbles into its original granular fragments, each
one of which melts separately. This accounts for the sudden
disappearance icebergs, which, instead of slowly dissolving into the
ocean, are often seen to fall to pieces and vanish at once.

Ice of this kind may be seen forming every winter on our sidewalks, on
the edge of the little ditches which drain them, or on the summits of
broad gateposts when capped with snow. Of such ice glaciers are
composed; but, in the glacier, another element comes in which we have
not considered as yet,--that of immense pressure in consequence of the
vast accumulations of snow within circumscribed spaces. We see the same
effects produced on a small scale, when snow is transformed into a
snowball between the hands. Every boy who balls a mass of snow in his
hands illustrates one side of glacial phenomena. Loose snow, light and
porous, and pure white from the amount of air contained in it, is in
this way presently converted into hard, compact, almost transparent ice.
This change will take place sooner, if the snow be damp at first,--but
if dry, the action of the hand will presently produce moisture enough to
complete the process. In this case, mere pressure produces the same
effect which, in the cases we have been considering above, was brought
about by alternate thawing and freezing,--only that in the latter the
ice is distinctly granular, instead of being uniform throughout, as when
formed under pressure. In the glaciers we have the two processes
combined. But the investigators of glacial phenomena have considered too
exclusively one or the other: some of them attributing glacial motion
wholly to the dilatation produced by the freezing of infiltrated
moisture in the mass of snow; others accounting for it entirely by
weight and pressure. There is yet a third class, who, disregarding the
real properties of ice, would have us believe, that, because tar, for
instance, is viscid when it moves, therefore ice is viscid because it
moves. We shall see hereafter that the phenomena exhibited in the onward
movement of glaciers are far more diversified than has generally been
supposed.

There is no chain of mountains in which the shape of the valleys is more
favorable to the formation of glaciers than the Alps. Contracted at
their lower extremity, these valleys widen upward, spreading into deep,
broad, trough-like depressions. Take, for instance, the valley of
Hassli, which is not more than half a mile wide where you enter it above
Meyringen; it opens gradually upward, till, above the Grimsel, at the
foot of the Finster-Aarhorn, it measures several miles across. These
huge mountain-troughs form admirable cradles for the snow, which
collects in immense quantities within them, and, as it moves slowly down
from the upper ranges, is transformed into ice on its way, and compactly
crowded into the narrower space below. At the lower extremity of the
glacier the ice is pure, blue and transparent, but, as we ascend, it
appears less compact, more porous and granular, assuming gradually the
character of snow, till in the higher regions the snow is as light, as
shifting, and incoherent, as the sand of the desert. A snow-storm on a
mountain-summit is very different from a snow-storm on the plain, on
account of the different degrees of moisture in the atmosphere. At great
heights, there is never dampness enough to allow the fine snow-crystals
to coalesce and form what are called "snow-flakes." I have even stood on
the summit of the Jungfrau when a frozen cloud filled the air with
ice-needles, while I could see the same cloud pouring down sheet of rain
upon Lauterbrunnen below. I remember this spectacle as one of the most
impressive I have witnessed in my long experience of Alpine scenery. The
air immediately about me seemed filled with rainbow-dust, for the
ice-needles glittered with a thousand hues under the decomposition of
light upon them, while the dark storm in the valley below offered a
strange contract to the brilliancy of the upper region in which I stood.
One wonder where even so much vapor as may be transformed into the
finest snow should come from at such heights. But the warm winds,
creeping up the sides of the valleys, the walls of which become heated
during the middle of the day, come laden with moisture which is changed
to a dry snow like dust as soon as it comes into contact with the
intense cold above.

Currents of warm air affect the extent of the glaciers, and influence
also the line of perpetual snow, which is by no means at the same level
even in neighboring localities. The size of glaciers, of course,
determines to a great degree the height at which they terminate, simply
because a small mass of ice will melt more rapidly, and at a lower
temperature, than a larger one. Thus, the small glaciers, such as those
of the Rothhorn or of Trift, above the Grimsel, terminate at a
considerable height above the plain, while the Mer de Glace, fed from
the great snow-caldrons of Mont Blanc, forces its way down to the bottom
of the valley of Chamouni, and the glacier of Grindelwald, constantly
renewed from the deep reservoirs where the Jungfrau hoards her vast
supplies of snow, descends to about four thousand feet above the
sea-level. But the glacier of the Aar, though also very large, comes to
a pause at about six thousand feet above the level of the sea; for the
south wind from the other side of the Alps, the warm sirocco of Italy,
blows across it, and it consequently melts at a higher level than either
the Mer de Glace or the Grindelwald. It is a curious fact, that in the
valley of Hassli the temperature frequently rises instead of falling as
you ascend; at the Grimsel, the temperature is at times higher than at
Meyringen below, where the warmer winds are not felt so directly. The
glacier of Aletsch, on the southern slope of the Jungfrau, and into
which many other glaciers enter, terminates also at a considerable
height, because it turns into the valley of the Rhone, through which the
southern winds blow constantly.

Under ordinary conditions, vegetation fades in these mountains at the
height of six thousand feet, but, in consequence of prevailing winds,
and the sheltering influence of the mountain-walls, there is no
uniformity in the limit of perpetual snow and ice. Where currents of
warm air are very constant, glaciers do not occur at all, even where
other circumstances are favorable to their formation. There are valleys
in the Alps far above six thousand feet which have no glaciers, and
where perpetual snow is seen only on their northern sides. These
contrasts in temperature lead to the most wonderful contrasts in the
aspect of the soil; summer and winter lie side by side, and bright
flowers look out from the edge of snows that never melt. Where the warm
winds prevail, there may be sheltered spots at a height of ten or eleven
thousand feet, isolated nooks opening southward where the most exquisite
flowers bloom in the midst of perpetual snow and ice; and occasionally I
have seen a bright little flower with a cap of snow over it that seemed
to be its shelter. The flowers give, indeed, a peculiar charm to these
high Alpine regions. Occurring often in beds of the same kind, forming
green, blue or yellow patches, they seem nestled close together in
sheltered spots, or even in fissures and chasms of the rock, where they
gather in dense quantities. Even in the sternest scenery of the Alps
some sign of vegetation lingers; and I remember to have found a tuft of
lichen growing on the only rock which pierced through the ice on the
summit of the Jungfrau. The absolute solitude, the intense stillness of
the upper Alps is most impressive; no cattle, no pasturage, no bird, nor
any sound of life,--and, indeed, even if there were, the rarity of the
air in these high regions is such that sound is hardly transmissible.
The deep repose, the purity of aspect of every object, the snow, broken
only by ridges of angular rocks, produce an effect no less beautiful
than solemn. Sometimes, in the midst of the wide expanse, one comes upon
a patch of the so-called red snow of the Alps. At a distance, one would
say that such a spot marked some terrible scene of blood, but, as you
come nearer, the hues are so tender and delicate, as they fade from deep
red to rose, and so die into the pure colorless snow around, that the
first impression is completely dispelled. This red snow is an organic
growth, a plant springing up in such abundance that it colors extensive
surfaces, just as the microscopic plants dye our pools with green in the
spring. It is an _Alga_ well known in the Arctics, where it forms wide
fields in the summer. With the above facts before us concerning the
materials of which glaciers are composed, we may now proceed to
consider their structure more fully in connection with their movements
and the effects they produce on the surfaces over which they extend. It
has already been stated that the ice of the glaciers has not the same
appearance everywhere, but differs according to the level at which it
stands. In consequence of this we distinguish three very distinct
regions in these frozen fields, the uppermost of which, upon the sides
of the steepest and highest slopes of the mountain-ridges, consists
chiefly of layers of snow piled one above another by the successive
snowfalls of the colder seasons, and which would remain in uniform
superposition but for the change to which they are subjected in
consequence of a gradual downward movement, causing the mass to descend
by slow degrees, while new accumulations in the higher regions annually
replace the snow which has been thus removed to an inferior level. We
shall consider hereafter the process by which this change of position is
brought about. For the present it is sufficient to state that such a
transfer, by which a balance is preserved in the distribution of the
snow, takes place in all glaciers, so that, instead of increasing
indefinitely in the upper regions, where on account of the extreme cold
there is little melting, they permanently preserve about the same
thickness, being yearly reduced by their downward motion in a proportion
equal to their annual increase by fresh additions of snow. Indeed, these
reservoirs of snow maintain themselves at the same level, much as a
stream, into which many rivulets empty, remains within its usual limits
in consequence of the drainage of the average supply. Of course, very
heavy rains or sudden thaws at certain seasons or in particular years
may cause an occasional overflow of such a stream; and irregularities of
the same kind are observed during certain years or at different periods
of the same year in the accumulations of snow, in consequence of which
the successive strata may vary in thickness. But in ordinary times
layers from six to eight feet deep are regularly added annually to the
accumulation of snow in the higher regions,--not taking into account, of
course, the heavy drifts heaped up in particular localities, but
estimating the uniform average increase over wide fields. This snow is
gradually transformed into more or less compact ice, passing through an
intermediate condition analogous to the slosh of our roads, and in that
condition chiefly occupies the upper part of the extensive troughs into
which these masses descend from the loftier heights. This region is
called the region of the _neve_. It is properly the birthplace of the
glaciers, for it is here that the transformation of the snow into ice
begins. The _neve_ ice, though varying in the degree of its compactness
and solidity, is always very porous and whitish in color, resembling
somewhat frozen slosh, while lower down in the region of the glacier
proper the ice is close, solid, transparent, and of a bluish tint.

But besides the differences in solidity and in external appearance,
there are also many other important changes taking place in the ice of
these different regions, to which we shall return presently. Such
modifications arise chiefly from the pressure to which it is subjected
in its downward progress, and to the alterations, in consequence of this
displacement, in the relative position of the snow- and ice-beds, as
well as to the influence exerted by the form of the valleys themselves,
not only upon the external aspect of the glaciers, but upon their
internal structure also. The surface of a glacier varies greatly in
character in these different regions. The uniform even surfaces of the
upper snow-fields gradually pass into a more undulating outline, the
pure white fields become strewn with dust and sand in the lower levels,
while broken bits of stone and larger fragments of rock collect upon
them, which assume a regular arrangement, and produce a variety of
features most startling and incomprehensible at first sight, but more
easily understood when studied in connection with the whole series of
glacial phenomena. They are then seen to be the consequence of the
general movement of the glacier, and of certain effects which the course
of the seasons, the action of the sun, the rain, the reflected heat from
the sides of the valley, or the disintegration of its rocky walls, may
produce upon the surface of the ice. In the next article we shall
consider in detail all these phenomena, and trace them in their natural
connection. Once familiar with these facts, it will not be difficult
correctly to appreciate the movement of the glacier and the cause of its
inequalities. We shall see, that, in consequence of the greater or less
rapidity in the movement of certain portions of the mass, its centre
progressing faster than its sides, and the upper, middle, and lower
regions of the same glacier advancing at different rates, the strata
which in the higher ranges of the snow-fields were evenly spread over
wide expanses, become bent and folded to such a degree that the
primitive stratification is nearly obliterated, while the internal mass
of the ice has also assumed new features under these new circumstances.
There is, indeed, as much difference between the newly formed beds of
snow in the upper region and the condition of the ice at the lower end
of a glacier as between a recent deposit of coral sand or a mud-bed in
an estuary and the metamorphic limestone or clay slate twisted and
broken as they are seen in the very chains of mountains from which the
glaciers descend. A geologist, familiar with all the changes to which a
bed of rock may be subjected from the time it was deposited in
horizontal layers up to the time when it was raised by Plutonic agencies
along the sides of a mountain-ridge, bent and distorted in a thousand
directions, broken through the thickness of its mass, and traversed by
innumerable fissures which are themselves filled with new materials,
will best be able to understand how the stratification of snow may be
modified by pressure and displacement so as finally to appear like a
laminated mass full of cracks and crevices, in which the original
stratification is recognized only by the practical student. I trust in
my next article I shall be able to explain intelligibly to my readers
even these extreme alterations in the condition of the primitive snow of
the Alpine summits.

* * * * *

TWO SCENES FROM THE LIFE OF BLONDEL.

SCENE I.--_Near a Castle in Germany._

'Twere no hard task, perchance, to win
The popular laurel for my song;
'Twere only to comply with sin,
And own the crown, though snatched by wrong:
Rather Truth's chaplet let me wear,
Though sharp as death its thorns may sting;
Loyal to Loyalty, I bear
No badge but of my rightful king.

Patient by town and tower I wait,
Or o'er the blustering moorland go;
I buy no praise at cheaper rate,
Or what faint hearts may fancy so:
For me, no joy in lady's bower,
Or hall, or tourney, will I sing,
Till the slow stars wheel round the hour
That crowns my hero and my king.

While all the land runs red with strife,
And wealth is won by peddler-crimes,
Let who will find content in life
And tinkle in unmanly rhymes:
I wait and seek; through dark and light,
Safe in my heart my hope I bring,
Till I once more my faith may plight
To him my whole soul owns her king.

When power is filched by drone and dolt,
And, with caught breath and flashing eye,
Her knuckles whitening round the bolt,
Vengeance leans eager from the sky,--
While this and that the people guess,
And to the skirts of praters cling,
Who court the crowd they should compress,--
I turn in scorn to seek my king.

Shut in what tower of darkling chance
Or dungeon of a narrow doom,
Dream'st thou of battle-axe and lance
That for the cross make crashing room?
Come! with strained eyes the battle waits
In the wild van thy mace's swing;
While doubters parley with their fates,
Make thou thine own and ours, my king!

Oh, strong to keep upright the old,
And wise to buttress with the new,
Prudent, as only are the bold,
Clear-eyed, as only are the true,
To foes benign, to friendship stern,
Intent to imp Law's broken wing,--
Who would not die, if death might earn
The right to kiss thy hand, my king?

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