A chapter on mountains will not be an inappropriate introduction to that
part of the world's history on which we are now entering, when the great
inequalities of the earth's surface began to make their appearance; and
before giving any special account of the geological succession in
Europe, I will say something of the formation of mountains in general,
and of the men whose investigations first gave us the clue to the
intricacies of their structure. It has been the work of the nineteenth
century to decipher the history of the mountains, to smooth out these
wrinkles in the crust of the earth, to show that there was a time when
they did not exist, to decide at least comparatively upon their age, and
to detect the forces which have produced them.
But while I speak of the reconstructive labors of the geologist with so
much confidence, because to my mind they reveal an intelligible
coherence in the whole physical history of the world, yet I am well
aware that there are many and wide gaps in our knowledge to be filled
up. All the attempts to represent the appearance of the earth in past
periods by means of geological maps are, of course, but approximations
of the truth, and will compare with those of future times, when the
phenomena are better understood, much as our present geographical maps,
the result of repeated surveys and of the most accurate measurements,
compare with those of the ancients.
Homer's world was a flat expanse, surrounded by ocean, of which Greece
was the centre. Asia Minor, the Ægean Islands, Egypt, part of Italy and
Sicily, the Mediterranean and the Black Sea filled out and completed his
map.
Hecatæus, the Greek historian and geographer, who lived more than five
hundred years before Christ, had not enlarged it much. He was, to be
sure, a voyager on the Mediterranean, and had an idea of the extent of
Italy. Acquaintance with Phoenician merchants also had enlarged his
knowledge of the world; Sardinia, Corsica, and Spain were known to him;
he was familiar with the Black and Red Seas; and though an indentation
on his map in the neighborhood of the Caspian would seem to indicate
that he was aware of the existence of this sea also, it is not otherwise
marked.
Herodotus makes a considerable advance beyond his predecessors: the
Caspian Sea has a place on his map; Asia is sketched out, including the
Persian Gulf with the large rivers pouring into it; and the course of
the Ganges is traced, though he makes it flow east and empty into the
Pacific, instead of turning southward and emptying into the Indian
Ocean.
Eratosthenes, two centuries before Christ, is the first geographer who
makes some attempt to determine the trend of the land and water,
presenting a suggestion that the earth is broader in one direction than
in the other. In his map, he adds also the geographical results derived
from the expeditions of Alexander the Great.
Ptolemy, who flourished in Alexandria in the reign of Hadrian, is the
next geographer of eminence, and he shows us something of Africa; for,
in his time, the Phoenicians, in their commercial expeditions, had
sailed far to the south, had reached the termination of Africa, with
ocean lying all around it, and had seen the sun to the north of them.
This last assertion, however, Ptolemy does not credit, and he is as
skeptical of the open ocean surrounding the extremity of Africa as
modern geographers and explorers have been of the existence of Kane's
open Arctic Sea. He believes that what the Phoenician traders took to
be the broad ocean must be part of an inland sea, corresponding to the
Mediterranean, with which he was so familiar. His map includes also
England, Ireland, and Scotland; and his Ultima Thule is, no doubt, the
Hebrides of our days.
Our present notions of the past periods of the world's history probably
bear about the same relation to the truth that these ancient
geographical maps bear to the modern ones. But this should not
discourage us, for, after all, those maps were in the main true as far
as they went; and as the ancient geographers were laying the foundation
for all our modern knowledge of the present conformation of the globe,
so are the geologists of the nineteenth century preparing the ground for
future investigators, whose work will be as far in advance of theirs as
are the delineations of Carl Ritter, the great master of physical
geography in our age, in advance of the map drawn by the old Alexandrian
geographer. We shall have our geological explorers and discoverers in
the lands and seas of past times, as we have had in the present,--our
Columbuses, our Captain Cooks, our Livingstones in geology, as we have
had in geography. There are undiscovered continents and rivers and
inland seas in the past world to exercise the ingenuity, courage, and
perseverance of men, after they shall have solved all the problems,
sounded all the depths, and scaled all the heights of the present
surface of the earth.
What has been done thus far is chiefly to classify the inequalities of
the earth's surface, and to detect the different causes which have
produced them. Foldings of the earth's crust, low hills, extensive
plains, mountain-chains and narrow valleys, broad table-lands and wide
valleys, local chimneys or volcanoes, river-beds, lake-basins, inland
seas,--such are some of the phenomena which, disconnected as they seem
at first glance, have nevertheless been brought under certain
principles, and explained according to definite physical laws.
Formerly, men looked upon the earth as a unit in time, as the result of
one creative act, with all its outlines established from the beginning.
It has been the work of modern science to show that its inequalities are
not contemporaneous or simultaneous, but successive, including a law of
growth,--that heat and cold, and the consequent expansion and
contraction of its crust, have produced wrinkles and folds upon the
surface, while constant oscillations, changes of level which are even
now going on, have modified its conformation, and moulded its general
outline through successive ages.
In thinking of the formation of the globe, we must at once free
ourselves from the erroneous impression that the crust of the earth is a
solid, steadfast foundation. So far from being immovable, it has been
constantly heaving and falling; and if we are not impressed by its
oscillations, it is because they are not so regular or so evident to our
senses as the rise and fall of the sea. The disturbances of the ocean,
and the periodical advance and retreat of its tides, are known to our
daily experience; we have seen it tossed into great billows by storms,
or placid as a lake when undisturbed. But the crust of the earth also
has had its storms, to which the tempests of the sea are as
nothing,--which have thrown up mountain waves twenty thousand feet high,
and fixed them where they stand, perpetual memorials of the convulsions
that upheaved them. Conceive an ocean wave that should roll up for
twenty thousand feet, and be petrified at its greatest height: the
mountains are but the gigantic waves raised on the surface of the land
by the geological tempests of past times. Besides these sudden storms of
the earth's surface, there have been its gradual upheavals and
depressions, going on now as steadily as ever, and which may be compared
to the regular action of the tides. These, also, have had their share in
determining the outlines of the continents, the height of the lands, and
the depth of the seas.
Leaving aside the more general phenomena, let us look now at the
formation of mountains especially. I have stated in a previous article
that the relative position of the stratified and unstratified rocks
gives us the key to their comparative age. To explain this I must enter
into some details respecting the arrangement of stratified deposits on
mountain-slopes and in mountain-chains, taking merely theoretical cases,
however, to illustrate phenomena which we shall meet with repeatedly in
actual facts, when studying special geological formations.
[Illustration: Fig. 1.]
We have, for instance, in Figure 1, a central granite mountain, with a
succession of stratified beds sloping against its sides, while at its
base are deposited a number of horizontal beds which have evidently
never been disturbed from the position in which they were originally
accumulated. The reader will at once perceive the method by which the
geologist decides upon the age of such a mountain. He finds the strata
upon its slopes in regular superposition, the uppermost belonging, we
will suppose, to the Triassic period; at its base he finds undisturbed
horizontal deposits, also in regular superposition, belonging to the
Jurassic and Cretaceous periods. Therefore, he argues, this mountain
must have been uplifted after the Triassic and all preceding deposits
were formed, since it has broken its way through them, and forced them
out of their natural position; and it must have been previous to the
Jurassic and Cretaceous deposits, since they have been accumulated
peacefully at its base, and have undergone no such perturbations.
The task of the geologist would be an easy one, if all the problems he
has to deal with were as simple as the case I have presented here; but
the most cursory glance at the intricacies of mountain-structure will
show us how difficult it is to trace the connection between the
phenomena. We must not form an idea of ancient mountain-upheavals from
existing active volcanoes, although the causes which produced them were,
in a modified and limited sense, the same. Our present volcanic
mountains are only chimneys, or narrow tunnels, as it were, pierced in
the thickness of the earth's surface, through which the molten lava
pours out, flowing over the edges and down the sides and hardening upon
the slopes, so as to form conical elevations. The mountain-ranges
upheaved by ancient eruptions, on the contrary, are folds of the earth's
surface, produced by the cooling of a comparatively thin crust upon a
hot mass. The first effect of this cooling process would be to cause
contractions; the next, to produce corresponding protrusions,--for,
wherever such a shrinking and subsidence of the crust occurred, the
consequent pressure upon the melted materials beneath must displace them
and force them upward. While the crust continued so thin that these
results could go on without very violent dislocations,--the materials
within easily finding an outlet, if displaced, or merely lifting the
surface without breaking through it,--the effect would be moderate
elevations divided by corresponding depressions. We have seen this kind
of action, during the earlier geological epochs, in the upheaval of the
low hills in the United States, leading to the formation of the
coal-basins.
On our return to the study of the American continent, we shall find in
the Alleghany chain, occurring at a later period, between the
Carboniferous and Triassic epochs, a good illustration of the same kind
of phenomena, though the action of the Plutonic agents was then much
more powerful, owing to the greater thickness of the crust and the
consequent increase of resistance. The folds forced upward in this chain
by the subsidence of the surface are higher than any preceding
elevations; but they are nevertheless a succession of parallel folds
divided by corresponding depressions, nor does it seem that the
displacement of the materials within the crust was so violent as to
fracture it extensively.
Even so late as the formation of the Jura mountains, between the
Jurassic and Cretaceous periods, the character of the upheaval is the
same, though there are more cracks at right angles with the general
trend of the chain, and here and there the masses below have broken
through. But the chain, as a whole consists of a succession of parallel
folds, forming long domes or arches, divided by longitudinal valleys.
The valleys represent the subsidences of the crust; the domes are the
corresponding protrusions resulting from these subsidences. The lines of
gentle undulation in this chain, so striking in contrast to the rugged
and abrupt character of the Alps immediately opposite, are the result of
this mode of formation.
After the crust of the earth had grown so thick, as it was, for
instance, in the later Tertiary periods, when the Alps were uplifted,
such an eruption could take place only by means of an immense force, and
the extent of the fracture would be in proportion to the resistance
opposed. It is hardly to be doubted, from the geological evidence
already collected, that the whole mountain-range from Western Europe
through the continent of Asia, including the Alps, the Caucasus, and the
Himalayas, was raised at the same time. A convulsion that thus made a
gigantic rent across two continents, giving egress to three such
mountain-ranges, must have been accompanied by a thousand fractures and
breaks in contrary directions. Such a pressure along so extensive a
tract could not be equal everywhere; the various thicknesses of the
crust, the greater or less flexibility of the deposits, the direction of
the pressure, would give rise to an infinite variety in the results;
accordingly, instead of the long, even arches, such as characterize the
earlier upheavals of the Alleghanies and the Jura, there are violent
dislocations of the surface, cracks, rents, and fissures in all
directions, transverse to the general trend of the upheaval, as well as
parallel with it.
Leaving aside for the moment the more baffling and intricate problems of
the later mountain-formations, I will first endeavor to explain the
simpler phenomena of the earlier upheavals.
[Illustration: Fig. 2.]
[Illustration: Fig. 3.]
Suppose that the melted materials within the earth are forced up against
a mass of stratified deposits, the direction of the pressure being
perfectly vertical, as represented in Figure 2. Such a pressure, if not
too violent, would simply lift the strata out of their horizontal
position into an arch or dome, (as in Figure 3,) and if continued or
repeated in immediate sequence, it would produce a number of such domes,
like long billows following each other, such as we have in the Jura. But
though this is the prevailing character of the range, there are many
instances even here where an unequal pressure has caused a rent at right
angles with the general direction of the upheaval; and one may trace the
action of this unequal pressure, from the unbroken arch, where it has
simply lifted the surface into a dome, to the granite crest, where the
melted rock has forced its way out and crystallized between the broken
beds that rest against its slopes.
[Illustration: Fig. 4.]
[Illustration: Fig. 5.]
In other instances, the upper beds alone may have been cracked, while
the continuity of the lower ones remains unbroken. In this case we have
a longitudinal valley on the top of a mountain-range, lying between the
two sides of the broken arch (as in Figure 4). Suppose, now, that there
are also transverse cracks across such a longitudinal split, we have
then a longitudinal valley with transverse valleys opening into it.
There are many instances of this in the Alleghanies and in the Jura.
Sometimes such transverse valleys are cut straight across, so that their
openings face each other; but often the cracks have taken place at
different points on the opposite sides, so that, in travelling through
such a transverse valley, you turn to the right or left, as the case may
be, where it enters the longitudinal valley, and follow that till you
come to another transverse valley opening into it from the opposite
side, through which you make your way out, thus crossing the chain in a
zigzag course (as in Figure 5). Such valleys are often much narrower at
some points than at others. There are even places in the Jura where a
rent in the chain begins with a mere crack,--a slit but just wide enough
to admit the blade of a knife; follow it for a while, and you may find
it spreading gradually into a wider chasm, and finally expanding into a
valley perhaps half a mile wide, or even wider.
By means of such cracks, rivers often pass through lofty
mountain-chains, and when we come to the investigation of the glacial
phenomena connected with the course of the Rhone, we shall find that
river following the longitudinal valley which separates the northern and
southern parts of the chain of the Alps till it comes to Martigny, where
it takes a sharp turn to the right through a transverse crack, flowing
northward between walls fourteen thousand feet high, till it enters the
Lake of Geneva, through which it passes, issuing at the other end, where
it takes a southern direction. For a long time mountains were supposed
to be the limitations of rivers, and old maps represent them always as
flowing along the valleys without ever passing through the
mountain-chains that divide them; but geology is fast correcting the
errors of geography, and a map which represents merely the external
features of a country, without reference to their structural relations,
is no longer of any scientific value.
It is not, however, by rents in mountain-chains alone, or by depressions
between them, that valleys are produced; they are often due to the
unequal hardness of the beds raised, and to their greater or less
liability to be worn away and disintegrated by the action of the rains.
This inequality in the hardness of the rocks forming a mountain-range
not only adds very much to the picturesqueness of outline, but also
renders the landscape more varied through the greater or less fertility
of the soil. On the hard rocks, where little soil can gather, there are
only pines, or a low, dwarfed growth; but on the rocks of softer
materials, more easily acted upon by the rain, a richer soil gathers,
and there, in the midst of mountain-scenery, may be found the most
fertile growth, the richest pasturage, the brightest flowers. Where such
a patch of arable soil has a southern exposure on a mountain-side, we
may have a most fertile vegetation at a great height and surrounded by
the dark pine-forests. Many of the pastures on the Alps, to which from
height to height the shepherds ascend with their flocks in the
summer,--seeking the higher ones as the lower become dry and
exhausted,--are due to such alternations in the character of the rocks.
In consequence of the influence of time, weather, atmospheric action of
all kinds, the apparent relation of beds has often become so completely
reversed that it is exceedingly difficult to trace their original
relation. Take, for instance, the following case. An eruption has
upheaved the strata over a given surface in such a manner as to lift
them into a mountain, cracking open the upper beds, but leaving the
lower ones unbroken. We have then a valley on a mountain-summit between
two crests resembling the one already shown in Figure 4. Such a narrow
passage between two crests may be changed in the course of time to a
wide expansive valley by the action of the rains, frosts, and other
disintegrating agents, and the relative position of the strata forming
its walls may seem to be entirely changed.
[Illustration: Fig. 6.]
Suppose, for example, that the two upper layers of the strata rent apart
by the upheaval of the mountain are limestone and sandstone, while the
third is clay and the fourth again limestone (as in Figure 6). Clay is
soft, and yields very readily to the action of rain. In such a valley
the edges of the strata forming its walls are of course exposed, and the
clay formation will be the first to give way under the action of
external influences. Gradually the rains wear away its substance till
it is completely hollowed out. By the disintegration of the bed beneath
them, the lime and sandstone layers above lose their support and crumble
down, and this process goes on, the clay constantly wearing away, and
the lime and sand above consequently falling in, till the upper beds
have receded to a great distance, the valley has opened to a wide
expanse instead of being inclosed between two walls, and the lowest
limestone bed now occupies the highest position on the mountain. Figure
7 represents one of the crests shown in Figure 6, after such a levelling
process has changed its outline.
[Illustration: Fig. 7.]
But the phenomena of eruptions in mountain-chains are far more difficult
to trace than the effects thus gradually produced. Plutonic action has,
indeed, played the most fantastic tricks with the crust of the earth,
which seems as plastic in the grasp of the fiery power hidden within it
as does clay in the hands of the sculptor.
We have seen that an equal vertical pressure from below produces a
regular dome,--or that, if the dome be broken through, a granite crest
is formed, with stratified materials resting against its slopes. But the
pressure has often been oblique instead of vertical, and then the slope
of the mountain is uneven, with a gradual ascent on one side and an
abrupt wall on the other; or in some instances the pressure has been so
lateral that the mountain is overturned and lies upon its side, and
there are still other cases where one mountain has been tilted over and
has fallen upon an adjoining one.
Sometimes, when beds have been torn asunder, one side of them has been
forced up above the other; and there are even instances where one side
of a mountain has been forced under the surface of the earth, while the
other has remained above. Stratified beds of rock are even found which
have been so completely capsized, that the layers, which were of course
deposited horizontally, now stand on end, side by side, in vertical
rows. I remember, after a lecture on some of these extravagances in
mountain-formations, a friend said to me, not inaptly,--"One can hardly
help thinking of these extraordinary contortions as a succession of
frantic frolics: the mountains seem like a troop of rollicking boys,
hunting one another in and out and up and down in a gigantic game of
hide-and-seek."
The width of the arch of a mountain depends in a great degree on the
thickness and flexibility of the beds of which it is composed. There is
not only a great difference in the consistency of stratified material,
but every variety in the thickness of the layers, from an inch, and even
less, to those measuring from ten or twenty to one hundred feet and more
in depth, without marked separation of the successive beds. This is
accounted for by the frequent alternations of subsidence and upheaval;
the continents having tilted sometimes in one direction, sometimes in
another, so that in certain localities there has been much water and
large deposits, while elsewhere the water was shallow and the deposits
consequently less. Thin and flexible strata have been readily lifted
into a sharp, abrupt arch with narrow base, while the thick and rigid
beds have been forced up more slowly in a wider arch with broader base.
Table-lands are only long unbroken folds of the earth's surface, raised
uniformly and in one direction. It is the same pressure from below,
which, when acting with more intense force in one direction, makes a
narrow and more abrupt fold, forming a mountain-ridge, but, when acting
over a wider surface with equal force, produces an extensive uniform
elevation. If the pressure be strong enough, it will cause cracks and
dislocations at the edges of such a gigantic fold, and then we have
table-lands between two mountain-chains, like the Gobi in Asia between
the Altai Mountains and the Himalayas, or the table-land inclosed
between the Rocky Mountains and the coast-range on the Pacific shore.
We do not think of table-lands as mountainous elevations, because their
broad, flat surfaces remind us of the level tracts of the earth; but
some of the table-lands are nevertheless higher than many
mountain-chains, as, for instance, the Gobi, which is higher than the
Alleghanies, or the Jura, or the Scandinavian Alps. One of Humboldt's
masterly generalizations was his estimate of the average thickness of
the different continents, supposing their heights to be levelled and
their depressions filled up, and he found that upon such an estimate
Asia would be much higher than America, notwithstanding the great
mountain-chains of the latter. The extensive table-land of Asia, with
the mountains adjoining it, outweighed the Alleghanies, the Rocky
Mountains, the Coast-Chain, and the Andes.
* * * * *
When we compare the present state of our knowledge of geological
phenomena with that which prevailed fifty years ago, it seems difficult
to believe that so great and important a change can have been brought
about in so short a time. It was on German soil and by German students
that the foundation was laid for the modern science of systematic
geology.
In the latter part of the eighteenth century, extensive mining
operations in Saxony gave rise to an elaborate investigation of the soil
for practical purposes. It was found that the rocks consisted of a
succession of materials following each other in regular sequence, some
of which were utterly worthless for industrial purposes, while others
were exceedingly valuable. The _Muschel-Kalk_ formation, so called from
its innumerable remains of shells, and a number of strata underlying it,
must be penetrated before the miners reached the rich veins of
_Kupferschiefer_ (copper slate), and below this came what was termed the
_Todtliegende_ (dead weight), so called because it contained no
serviceable materials for the useful arts, and had to be removed before
the valuable beds of coal lying beneath it, and making the base of the
series, could be reached. But while the workmen wrought at these
successive layers of rock to see what they would yield for practical
purposes, a man was watching their operations who considered the crust
of the earth from quite another point of view.
Abraham Gottlob Werner was born more than a century ago in Upper
Lusatia. His very infancy seemed to shadow forth his future studies, for
his playthings were the minerals he found in his father's forge. At a
suitable age he was placed at the mining school of Freiberg in Saxony,
and having, when only twenty-four years of age, attracted attention in
the scientific world by the publication of an "Essay on the Characters
of Minerals," he was soon after appointed to the professorship of
mineralogy in Freiberg. His lot in life could not have fallen in a spot
more advantageous for his special studies, and the enthusiasm with which
he taught communicated itself to his pupils, many of whom became his
devoted disciples, disseminating his views in their turn with a zeal
which rivalled the master's ardor.
Werner took advantage of the mining operations going on in his
neighborhood, the blasting, sinking of shafts, etc., to examine
critically the composition of the rocks thus laid open, and the result
of his analysis was the establishment of the Neptunic school of geology
alluded to in a previous article, and so influential in science at the
close of the eighteenth and the opening of the nineteenth century. From
the general character of these rocks, as well as the number of marine
shells contained in them, he convinced himself that the whole series,
including the Coal, the _Todtliegende_, the _Kupferschiefer_, the
_Zechstein_, the Red Sandstone, and the _Muschel-Kalk_, had been
deposited under the agency of water, and were the work of the ocean.
Thus far he was right, with the exception that he did not include the
local action of fresh water in depositing materials, afterwards traced
by Cuvier and Brogniart in the Tertiary deposits about Paris. But from
these data he went a step too far, and assumed that all rocks, except
the modern lavas, must have been accumulated by the sea,--believing even
the granites, porphyries, and basalts to have been deposited in the
ocean and crystallized from the substances it contained in solution.
But, in the mean time, James Hutton, a Scotch geologist, was looking at
phenomena of a like character from a very different point of view. In
the neighborhood of Edinburgh, where he lived, was an extensive region
of trap-rock,--that is, of igneous rock, which had forced itself through
the stratified deposits, sometimes spreading in a continuous sheet over
large tracts, or splitting them open and tilling all the interstices and
cracks so formed. Thus he saw igneous rocks not only covering or
underlying stratified deposits, but penetrating deep into their
structure, forming dikes at right angles with them, and presenting, in
short, all the phenomena belonging to volcanic rocks in contact with
stratified materials. He again pushed his theory too far, and, inferring
from the phenomena immediately about him that heat had been the chief
agent in the formation of the earth's crust, he was inclined to believe
that the stratified materials also were in part at least due to this
cause. I have alluded in a former number to the hot disputes and
long-contested battles of geologists upon this point. It was a pupil of
Werner's who at last set at rest this much vexed question.
At the age of sixteen, in the year 1790, Leopold von Buch was placed
under Werner's care at the mining school of Freiberg. Werner found him a
pupil after his own heart. Warmly adopting his teacher's theory, he
pursued his geological studies with the greatest ardor, and continued
for some time under the immediate influence and guidance of the Freiberg
professor. His university-studies over, however, he began to pursue his
investigations independently, and his geological excursions led him into
Italy, where his confidence in the truth of Werner's theory began to be
shaken. A subsequent visit to the region of extinct volcanoes in
Auvergne, in the South of France, convinced him that the aqueous theory
was at least partially wrong, and that fire had been an active agent in
the rock-formations of past times. This result did not change the
convictions of his master, Werner, who was too old or too prejudiced to
accept the later views, which were nevertheless the result of the
stimulus he himself had given to geological investigations.
But Von Buch was indefatigable. For years he lived the life of an
itinerant geologist. With a shirt and a pair of stockings in his pocket
and a geological hammer in his hand he travelled all over Europe on
foot. The results of his foot-journey to Scandinavia were among his most
important contributions to geology. He went also to the Canary Islands;
and it is in his extensive work on the geological formations of these
islands that he showed conclusively not only the Plutonic character of
all unstratified rocks, but also that to their action upon the
stratified deposits the inequalities of the earth's surface are chiefly
due. He first demonstrated that the melted masses within the earth had
upheaved the materials deposited in layers upon its surface, and had
thus formed the mountains.
No geologist has ever collected a larger amount of facts than Von Buch,
and to him we owe a great reform not only in geological principles, but
in methods of study also. An amusing anecdote is told of him, as
illustrating his untiring devotion to his scientific pursuits. In
studying the rocks, he had become engaged also in the investigation of
the fossils contained in them. He was at one time especially interested
in the _Terebratulæ_ (fossil shells), and one evening in Berlin, where
he was engaged in the study of these remains, he came across a notice
in a Swedish work of a particular species of that family which he could
not readily identify without seeing the original specimens. The next
morning Von Buch was missing, and as he had invited guests to dine with
him, some anxiety was felt on account of his non-appearance. On inquiry,
it was found that he was already far on his way to Sweden: he had
started by daylight on a pilgrimage after the new, or rather the old,
_Terebratula_. I tell the story as I heard it from one of the
disappointed guests.
All great natural phenomena impressed him deeply. On one occasion it was
my good fortune to make one of a party from the "Helvetic Association
for the Advancement of Science" on an excursion to the eastern extremity
of the Lake of Geneva. I well remember the expressive gesture of Von
Buch, as he faced the deep gorge through which the Rhone issues from the
interior of the Alps. While others were chatting and laughing about him,
he stood for a moment absorbed in silent contemplation of the grandeur
of the scene, then lifted his hat and bowed reverently before the
mountains.
Next to Von Buch, no man has done more for modern geology than Elie de
Beaumont, the great French geologist. Perhaps the most important of his
generalizations is that by which he has given us the clue to the
limitation of the different epochs in past times by connecting them with
the great revolutions in the world's history. He has shown us that the
great changes in the aspect of the globe, as well as in its successive
sets of animals, coincide with the mountain-upheavals.
I might add a long list of names, American as well as European, which
will be forever honored in the history of science for their
contributions to geology in the last half-century. But I have intended
only to close this chapter on mountains with a few words respecting the
men who first investigated their intimate structural organization, and
established methods of study in reference to them now generally adopted
throughout the scientific world. In my next article I shall proceed to
give some account of special geological formations in Europe, and the
gradual growth of that continent.