OF THE MATERIALS OF MOUNTAINS:--FIRST, COMPACT CRYSTALLINES.
Sec. 1. In the early days of geological science, the substances which
composed the crust of the earth, as far as it could be examined, were
supposed to be referable to three distinct classes: the first consisting
of rocks which not only supported all the rest, but from which all the
rest were derived, therefore called "Primary;" the second class
consisting of rocks formed of the broken fragments or altered substance
of the primary ones, therefore called "Secondary;" and, thirdly, rocks
or earthy deposits formed by the ruins and detritus of both primary and
secondary rocks, called, therefore, "Tertiary." This classification was
always, in some degree, uncertain; and has been lately superseded by
more complicated systems, founded on the character of the fossils
contained in the various deposits, and on the circumstances of position,
by which their relative ages are more accurately ascertainable. But the
original rude classification, though of little, if any, use for
scientific purposes, was based on certain broad and conspicuous
phenomena, which it brought clearly before the popular mind. In this way
it may still be serviceable, and ought, I think, to be permitted to
retain its place, as an introduction to systems more defined and
authoritative.
Sec. 2. For the fact is, that in approaching any large mountain range, the
ground over which the spectator passes, if he examine it with any
intelligence, will almost always arrange itself in his mind under three
great heads. There will be, first, the ground of the plains or valleys
he is about to quit, composed of sand, clay, gravel, rolled stones, and
variously mingled soils; which, if he has any opportunity,--at the banks
of a stream, or the sides of a railway cutting,--to examine to any
depth, he will find arranged in beds exactly resembling those of modern
sand-banks or sea-beaches, and appearing to have been formed under such
natural laws as are in operation daily around us. At the outskirts of
the hill district, he may, perhaps, find considerable eminences, formed
of these beds of loose gravel and sand; but, as he enters into it
farther, he will soon discover the hills to be composed of some harder
substance, properly deserving the name of rock, sustaining itself in
picturesque forms, and appearing, at first, to owe both its hardness and
its outlines to the action of laws such as do not hold at the present
day. He can easily explain the nature, and account for the distribution,
of the banks which overhang the lowland road, or of the dark earthy
deposits which enrich the lowland pasture; but he cannot so distinctly
imagine how the limestone hills of Derbyshire and Yorkshire were
hardened into their stubborn whiteness, or raised into their cavernous
cliffs. Still, if he carefully examines the substance of these more
noble rocks, he will, in nine cases out of ten, discover them to be
composed of fine calcareous dust, or closely united particles of sand;
and will be ready to accept as possible, or even probable, the
suggestion of their having been formed, by slow deposit, at the bottom
of deep lakes and ancient seas, under such laws of Nature as are still
in operation.
Sec. 3. But, as he advances yet farther into the hill district, he finds
the rocks around him assuming a gloomier and more majestic condition.
Their tint darkens; their outlines become wild and irregular; and
whereas before they had only appeared at the roadside in narrow ledges
among the turf, or glanced out from among the thickets above the brooks
in white walls and fantastic towers, they now rear themselves up in
solemn and shattered masses far and near; softened, indeed, with strange
harmony of clouded colors, but possessing the whole scene with their
iron spirit; and rising, in all probability, into eminences as much
prouder in actual elevation than those of the intermediate rocks, as
more powerful in their influence over every minor feature of the
landscape.
Sec. 4. And when the traveller proceeds to observe closely the materials of
which these noble ranges are composed, he finds also a complete change
in their internal structure. They are no longer formed of delicate sand
or dust--each particle of that dust the same as every other, and the
whole mass depending for its hardness merely on their closely cemented
unity; but they are now formed of several distinct substances, visibly
unlike each other; and not _pressed_ but _crystallized_ into one
mass,--crystallized into a unity far more perfect than that of the dusty
limestone, but yet without the least mingling of their several natures
with each other. Such a rock, freshly broken, has a spotty, granulated,
and, in almost all instances, sparkling, appearance; it requires a much
harder blow to break it than the limestone or sandstone; but, when once
thoroughly shattered, it is easy to separate from each other the various
substances of which it is composed, and to examine them in their
individual grains or crystals; of which each variety will be found to
have a different degree of hardness, a different shade of color, and a
different character of form.
But this examination will not enable the observer to comprehend the
method either of their formation or aggregation, at least by any process
such as he now sees taking place around him; he will at once be driven
to admit that some strange and powerful operation has taken place upon
these rocks, different from any of which he is at present cognizant; and
farther inquiry will probably induce him to admit, as more than
probable, the supposition that their structure is in great part owing to
the action of enormous heat prolonged for indefinite periods.
Sec. 5. Now, although these three great groups of rocks do indeed often
pass into each other by imperceptible gradations, and although their
peculiar aspect is never a severe indication of their relative ages, yet
their characters are for the most part so defined as to make a strong
impression on the mind of an ordinary observer, and their age is also
for the most part approximately indicated by their degrees of hardness,
and crystalline aspect. It does, indeed, sometimes happen that a soft
and slimy clay will pass into a rock like Aberdeen granite by
transitions so subtle that no point of separation can be determined; and
it very often happens that rocks like Aberdeen granite are of more
recent formation than certain beds of sandstone and limestone. But, in
spite of all these uncertainties and exceptions, I believe that unless
actual pains be taken to efface from the mind its natural impressions,
the idea of three great classes of rocks and earth will maintain its
ground in the thoughts of the general observer; that whether he desire
it or not, he will find himself throwing the soft and loose clays and
sands together under one head; placing the hard rocks, of a dull,
compact, homogeneous substance, under another head; and the hardest
rocks, of a crystalline, glittering, and various substance, under a
third head; and having done this, he will also find that, with certain
easily admissible exceptions, these three classes of rocks are, in every
district which he examines, of three different ages; that the softest
are the youngest, the hard and homogeneous ones are older, and the
crystalline are the oldest; and he will, perhaps, in the end, find it a
somewhat inconvenient piece of respect to the complexity and accuracy of
modern geological science, if he refuse to the three classes, thus
defined in his imagination, their ancient title of Tertiary, Secondary,
and Primary.
Sec. 6. But however this may be, there is one lesson evidently intended to
be taught by the different characters of these rocks, which we must not
allow to escape us. We have to observe, first, the state of perfect
powerlessness, and loss of all beauty, exhibited in those beds of earth
in which the separated pieces or particles are entirely independent of
each other, more especially in the gravel whose pebbles have all been
_rolled into one shape_: secondly, the greater degree of permanence,
power, and beauty possessed by the rocks whose component atoms have some
affection and attraction for each other, though all of one kind; and
lastly, the utmost form and highest beauty of the rocks in which the
several atoms have all _different shapes_, _characters_, and _offices_;
but are inseparably united by some fiery process which has purified them
all.
It can hardly be necessary to point out how these natural ordinances
seem intended to teach us the great truths which are the basis of all
political science; how the polishing friction which separates, the
affection which binds, and the affliction that fuses and confirms, are
accurately symbolized by the processes to which the several ranks of
hills appear to owe their present aspect; and how, even if the knowledge
of those processes be denied to us, that present aspect may in itself
seem no imperfect image of the various states of mankind: first, that
which is powerless through total disorganization; secondly, that which,
though united, and in some degree powerful, is yet incapable of great
effort or result, owing to the too great similarity and confusion of
offices, both in ranks and individuals; and finally, the perfect state
of brotherhood and strength in which each character is clearly
distinguished, separately perfected, and employed in its proper place
and office.
Sec. 7. I shall not, however, so oppose myself to the views of our leading
geologists as to retain here the names of Primary, Secondary, and
Tertiary rocks. But as I wish the reader to keep the ideas of the three
classes clearly in his mind, I will ask his leave to give them names
which involve no theory, and can be liable, therefore, to no great
objections. We will call the hard, and (generally) central, masses
Crystalline Rocks, because they almost always present an appearance of
crystallization. The less hard substances, which appear compact and
homogeneous, we will call Coherent Rocks, and for the scattered debris
we will use the general term Diluvium.
Sec. 8. All these substances agree in one character, that of being more or
less soft and destructible. One material, indeed, which enters largely
into the composition of most of them, flint, is harder than iron; but
even this, their chief source of strength, is easily broken by a sudden
blow; and it is so combined in the large rocks with softer substances,
that time and the violence of the weather invariably produce certain
destructive effects on their masses. Some of them become soft, and
moulder away; others break, little by little, into angular fragments or
slaty sheets; but all yield in some way or other; and the problem to be
solved in every mountain range appears to be, that under these
conditions of decay, the cliffs and peaks may be raised as high, and
thrown into as noble forms, as is possible, consistently with an
effective, though not perfect permanence, and a general, though not
absolute security.
Sec. 9. Perfect permanence and absolute security were evidently in nowise
intended.[42] It would have been as easy for the Creator to have made
mountains of steel as of granite, of adamant as of lime; but this was
clearly no part of the Divine counsels: mountains were to be
destructible and frail; to melt under the soft lambency of the
streamlet; to shiver before the subtle wedge of the frost; to wither
with untraceable decay in their own substance; and yet, under all these
conditions of destruction, to be maintained in magnificent eminence
before the eyes of men.
Nor is it in any wise difficult for us to perceive the beneficent
reasons for this appointed frailness of the mountains. They appear to be
threefold: the first, and the most important, that successive soils
might be supplied to the plains, in the manner explained in the last
chapter, and that men might be furnished with a material for their works
of architecture and sculpture, at once soft enough to be subdued, and
hard enough to be preserved; the second, that some sense of danger might
always be connected with the most precipitous forms, and thus increase
their sublimity; and the third, that a subject of perpetual interest
might be opened to the human mind in observing the changes of form
brought about by time on these monuments of creation.
In order, therefore, to understand the method in which these various
substances break, so as to produce the forms which are of chief
importance in landscape, as well as the exquisite adaptation of all
their qualities to the service of men, it will be well that I should
take some note of them in their order; not with any mineralogical
accuracy, but with care enough to enable me hereafter to explain,
without obscurity, any phenomena dependent upon such peculiarities of
substance.
1. CRYSTALLINE ROCKS.
Sec. 10. 1st. CRYSTALLINE ROCKS.--In saying, above, that the hardest rocks
generally presented an appearance of "crystallization," I meant a
glittering or granulated look, somewhat like that of a coarse piece of
freshly broken loaf sugar.
Are always Compound.
But this appearance may also exist in rocks of uniform and softer
substance, such as statuary marble, of which freshly broken pieces, put
into a sugar-basin, cannot be distinguished by the eye from the real
sugar. Such rocks are truly crystalline in structure; but the group to
which I wish to limit the term "crystalline," is not only thus
granulated and glittering, but is always composed of at least two,
usually three or four, substances, intimately mingled with each other in
the form of small grains or crystals, and giving the rock a more or less
speckled or mottled look, according to the size of the crystals and
their variety of color. It is a law of nature, that whenever rocks are
to be employed on hard service, and for great purposes, they shall be
thus composed. And there appear to be two distinct providential reasons
for this.
Sec. 11. The first, that these crystalline rocks being, as we saw above,
generally the oldest and highest, it is from them that other soils of
various kinds must be derived; and they were therefore made a kind of
storehouse, from which, wherever they were found, all kinds of treasures
could be developed necessary for the service of man and other living
creatures. Thus the granite of Mont Blanc is a crystalline rock composed
of four substances; and in these four substances are contained the
elements of nearly all kinds of sandstone and clay, together with
potash, magnesia, and the metals of iron and manganese. Wherever the
smallest portion of this rock occurs, a certain quantity of each of
these substances may be derived from it, and the plants and animals
which require them sustained in health.
The second reason appears to be that rocks composed in this manner are
capable of more interesting variety in form than any others; and as they
were continually to be exposed to sight in the high ranges, they were so
prepared as to be always as interesting and beautiful as possible.
And divisible into two classes, Compact Crystallines and Slaty
Crystallines.
Sec. 12. These crystalline or spotted rocks we must again separate into two
great classes, according to the arrangement, in them, of the particles
of a substance called mica. It is not present in all of them; but when
it occurs, it is usually in large quantities, and a notable source of
character. It varies in color, occurring white, brown, green, red, and
black; and in aspect, from shining plates to small dark grains, even
these grains being seen, under a magnifier, to be composed of little
plates, like pieces of exceedingly thin glass; but with this great
difference from glass, that, whether large or small, the plates will not
easily break _across_, but are elastic, and capable of being bent into a
considerable curve; only if pressed with a knife upon the edge, they
will separate into any number of thinner plates, more and more elastic
and flexible according to their thinness, and these again into others
still finer; there seeming to be no limit to the possible subdivision
but the coarseness of the instrument employed.
[Illustration: FIG. 3.]
Sec. 13. Now, when these crystals or grains, represented by the black spots
and lines in Fig. 3, lie as they do at _a_ in that figure, in all
directions, cast hither and thither among the other materials of the
stone,--sometimes on their faces, sometimes on their sides, sometimes on
their edges,--they give the rock an irregularly granulated appearance
and structure, so that it will break with equal ease in any direction;
but if these crystals lie all one way, with their sides parallel, as at
_b_, they give the rock a striped or slaty look, and it will most
readily break in the direction in which they lie, separating itself into
folia or plates, more or less distinctly according to the quantity of
mica in its mass. In the example Fig. 4, a piece of rock from the top of
Mont Breven, there are very few of them, and the material with which
they are surrounded is so hard and compact that the whole mass breaks
irregularly, like a solid flint, beneath the hammer; but the plates of
mica nevertheless influence the fracture on a large scale, and occasion,
as we shall see hereafter, the peculiar form of the precipice at the
summit of the mountain.[43]
The rocks which are destitute of mica, or in which the mica lies
irregularly, or in which it is altogether absent, I shall call Compact
Crystallines. The rocks in which the mica lies regularly I shall call
Slaty Crystallines.
[Illustration: FIG. 4.]
COMPACT CRYSTALLINES.
Sec. 14. 1st. Compact Crystallines.--Under this head are embraced the large
group of the granites, syenites, and porphyries,--rocks which all agree
in the following particulars:--
Their first characteristic. _Speckledness._
A. Variety of color.--The method of their composition out of different
substances necessitates their being all more or less spotted or dashed
with various colors; there being generally a prevalent ground color,
with other subordinate hues broken over it, forming, for the most part,
tones of silver grey, of warm but subdued red, or purple. Now, there is
in this a very marvellous provision for the beauty of the central
ranges. Other rocks, placed lower among the hills, receive color upon
their surfaces from all kinds of minute vegetation; but these higher and
more exposed rocks are liable to be in many parts barren; and the wild
forms into which they are thrown necessitate their being often freshly
broken, so as to bring their pure color, untempered in anywise, frankly
into sight. Hence it is appointed that this color shall not be raw or
monotonous, but composed--as all beautiful color must be composed--by
mingling of many hues in one. Not that there is any aim at _attractive_
beauty in these rocks; they are intended to constitute solemn and
desolate scenes; and there is nothing delicately or variously disposed
in their colors. Such beauty would have been inconsistent with their
expression of power and terror, and it is reserved for the marbles and
other rocks of inferior office. But their color is grave and perfect;
closely resembling, in many cases, the sort of hue reached by
cross-chequering in the ground of fourteenth-century manuscripts, and
peculiarly calculated for distant effects of light; being, for the most
part, slightly warm in tone, so as to receive with full advantage the
red and orange rays of sunlight. This warmth is almost always farther
aided by a glowing orange color, derived from the decomposition of the
iron which, though in small quantity, usually is an essential element in
them: the orange hue forms itself in unequal veins and spots upon the
surfaces which have been long exposed, more or less darkening them; and
a very minute black lichen,--so minute as to look almost like spots of
dark paint,--a little opposed and warmed by the golden Lichen
geographicus, still farther subdues the paler hues of the highest
granite rocks. Now, when a surface of this kind is removed to a distance
of four or five miles, and seen under warm light through soft air, the
orange becomes russet, more or less inclining to pure red, according to
the power of the rays: but the black of the lichen becomes pure dark
blue; and the result of their combination is that peculiar reddish
purple which is so strikingly the characteristic of the rocks of the
higher Alps. Most of the travellers who have seen the Valley of Chamouni
carry away a strong impression that its upper precipices are of red
rock. But they are, without exception, of a whitish grey, toned and
raised by this united operation of the iron, the lichen, and the light.
Sec. 15. I have never had an opportunity of studying the effects of these
tones upon rocks of porphyry; but the beautiful color of that rock in
its interior substance has rendered it one of the favorite materials of
the architects of all ages, in their most costly work. Not that all
porphyry is purple; there are green and white porphyries, as there are
yellow and white roses; but the first idea of a porphyry rock is that it
shall be purple,--just as the first idea of a rose is that it shall be
red. The purple inclines always towards russet[44] rather than blue, and
is subdued by small spots of grey or white. This speckled character,
common to all the crystalline rocks, fits them, in art, for large and
majestic work; it unfits them for delicate sculpture; and their second
universal characteristic is altogether in harmony with this consequence
of their first.
Their second characteristic. _Toughness._
Sec. 16. This second characteristic is a tough hardness, not a brittle
hardness, like that of glass or flint, which will splinter violently at
a blow in the most unexpected directions; but a grave hardness, which
will bear many blows before it yields, and when it is forced to yield at
last, will do so, as it were, in a serious and thoughtful way; not
spitefully, nor uselessly, nor irregularly, but in the direction in
which it is wanted, and where the force of the blow is directed--there,
and there only. A flint which receives a shock stronger than it can
bear, gives up everything at once, and flies into a quantity of pieces,
each piece full of flaws. But a piece of granite seems to say to itself,
very solemnly: "If these people are resolved to split me into two
pieces, that is no reason why I should split myself into three. I will
keep together as well as I can, and as long as I can; and if I must fall
to dust at last, it shall be slowly and honorably; not in a fit of
fury." The importance of this character, in fitting the rock for human
uses, cannot be exaggerated: it is essential to such uses that it should
be hard, for otherwise it could not bear enormous weights without being
crushed; and if, in addition to this hardness, it had been brittle, like
glass, it could not have been employed except in the rudest way, as
flints are in Kentish walls. But now it is possible to cut a block of
granite out of its quarry to exactly the size we want; and that with
perfect ease, without gunpowder, or any help but that of a few small
iron wedges, a chisel, and a heavy hammer. A single workman can detach a
mass fifteen or twenty feet long, by merely drilling a row of holes, a
couple of inches deep, and three or four inches apart, along the
surface, in the direction in which he wishes to split the rock, and then
inserting wedges into each of these holes, and striking them,
consecutively, with small, light, repeated blows along the whole row.
The granite rends, at last, along the line, quite evenly, requiring very
little chiselling afterwards to give the block a smooth face.
Sec. 17. This after-chiselling, however, is necessarily tedious work, and
therefore that condition of speckled color, which is beautiful if
exhibited in broad masses, but offensive in delicate forms, exactly
falls in with the conditions of _possible_ sculpture. Not only is it
more laborious to carve granite delicately, than a softer rock; but it
is physically impossible to bring it into certain refinements of form.
It cannot be scraped and touched into contours, as marble can; it must
be struck hard, or it will not yield at all; and to strike a delicate
and detached form hard, is to break it. The detached fingers of a
delicate hand, for instance, cannot, as far as I know, be cut in
granite. The smallest portion could not be removed from them without a
strength of blow which would break off the finger. Hence the sculptor of
granite is forced to confine himself to, and to seek for, certain types
of form capable of expression in his material; he is naturally driven to
make his figures simple in surface, and colossal in size, that they may
bear his blows; and this simplicity and magnitude are exactly the
characters necessary to show the granitic or porphyritic color to the
best advantage. And thus we are guided, almost forced, by the laws of
nature, to do right in art. Had granite been white, and marble speckled
(and why should this not have been, but by the definite Divine
appointment for the good of man?), the huge figures of the Egyptian
would have been as oppressive to the sight as cliffs of snow, and the
Venus de Medicis would have looked like some exquisitely graceful
species of frog.
Their third characteristic. _Purity in decomposition._
Sec. 18. The third universal characteristic of these rocks is their
decomposition into the purest sand and clay. Some of them decompose
spontaneously, though slowly, on exposure to weather; the greater number
only after being mechanically pulverized; but the sand and clay to which
by one or the other process they are reducible, are both remarkable for
their purity. The clay is the finest and best that can be found for
porcelain; the sand often of the purest white, always lustrous and
bright in its particles. The result of this law is a peculiar aspect of
purity in the landscape composed of such rocks. It cannot become muddy,
or foul, or unwholesome. The streams which descend through it may indeed
be opaque, and as white as cream with the churned substance of the
granite; but their water, after this substance has been thrown down, is
good and pure, and their shores are not slimy or treacherous, but of
pebbles, or of firm and sparkling sand. The quiet streams, springs, and
lakes are always of exquisite clearness, and the sea which washes a
granite coast is as unsullied as a flawless emerald. It is remarkable to
what extent this intense purity in the country seems to influence the
character of its inhabitants. It is almost impossible to make a cottage
built in a granite country look absolutely miserable. Rough it may
be,--neglected, cold, full of aspect of hardship,--but it never can look
_foul_; no matter how carelessly, how indolently, its inhabitants may
live, the water at their doors will not stagnate, the soil beneath their
feet will not allow itself to be trodden into slime, the timbers of
their fences will not rot, they cannot so much as dirty their faces or
hands if they try; do the worst they can, there will still be a feeling
of firm ground under them, and pure air about them, and an inherent
wholesomeness in their abodes which it will need the misery of years to
conquer. And, as far as I remember, the inhabitants of granite countries
have always a force and healthiness of character, more or less abated
or modified, of course, according to the other circumstances of their
life, but still definitely belonging to them, as distinguished from the
inhabitants of the less pure districts of the hills.
These, then, are the principal characters of the compact crystallines,
regarded in their minor or detached masses. Of the peculiar forms which
they assume we shall have to speak presently; meantime, retaining these
general ideas touching their nature and substance, let us proceed to
examine, in the same point of view, the neighboring group of slaty
crystallines.
FOOTNOTES
[42] I am well aware that to the minds of many persons nothing bears
a greater appearance of presumption than any attempt at reasoning
respecting the purposes of the Divine Being; and that in many cases
it would be thought more consistent with the modesty of humanity to
limit its endeavor to the ascertaining of physical causes than to
form conjectures respecting Divine intentions. But I believe this
feeling to be false and dangerous. Wisdom can only be demonstrated
in its ends, and goodness only perceived in its motives. He who in a
morbid modesty supposes that he is incapable of apprehending any of
the purposes of God, renders himself also incapable of witnessing
his wisdom; and he who supposes that favors may be bestowed without
intention, will soon learn to receive them without gratitude.
[43] See Appendix 2. Slaty Cleavage.
[44] As we had to complain of Dante for not enough noticing the
colors of rocks in wild nature, let us do him the justice to refer
to his noble symbolic use of their colors when seen in the hewn
block.
"The lowest stair was marble white, so smooth
And polished that therein my mirrored form
Distinct I saw. The next of hue more dark
Than sablest grain, a rough and singed block,
Cracked lengthwise and across. The third, that lay
Massy above, seemed porphyry, that flamed
Red as the life-blood spouting from a vein."
This stair is at the gate of Purgatory. The white step means
sincerity of conscience; the black, contrition; the purple (I
believe), pardon by the Atonement.