telluric sphere of nature, it will be expedient to cast a preliminary glance
over the relations in space of solids and fluids, the form of the Earth, its
mean density, and the partial distribution of this density in the interior
of our planet, its temperature and its electro-magnetic tension. From the
consideration of these relations in space, and of the forces inherent in
matter, we shall pass to the reaction of the interior on the exterior of our
globe; and to the special consideration of a universally distributed natural
power -- subterranean heat; to the phenomena of earthquakes, exhibited in
unequally expanded circles of commotion, which are not referable to the
action of dynamic laws alone; to the springing forth of hot wells; and,
lastly, to the more powerful actions of volcanic processes. The crust of
the Earth, which may scarcely have been perceptibly elevated by the sudden
and repeated, or almost uninterrupted shocks by which it has been moved from
below, undergoes, nevertheless, great changes in the course of centuries in
the relations of the elevation of solid portions, when compared with the
surface of the liquid parts, and even in the form of the bottom of the sea.
In this manner simultaneous temporary or permanent fissures are opened, by
which the interior of the Earth is brought in contact with the external
atmosphere. Molten masses, rising from an unknown depth, flow in narrow
streams along the declivity of mountains, rushing impetuously onward, or
moving slowly and gently, until the fiery source is quenched in the midst of
exhalations, and the lava becomes incrusted, as it were, by
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the solidification of its outer surface. New masses of rocks are thus
formed before our eyes, while the older ones are in their turn converted
into other forms by the greater or lesser agency of Platonic forces. Even
where no disruption takes place the crystalline moleculres are displaced,
combining to form bodies of denser texture. The water presents structures
of a totally different nature, as, for instance, concretions of animal and
vegetable remains, of earthy, calcareous, or aluminous precipitates,
agglomerations of finely-pulverized mineral bodies, covered with layers of
the silicious shields of infusoria, and with transported soils containing
the bones of fossil animal forms of a more ancient world. The study of the
strata which are so differently formed and arranged before our eyes, and of
all that has been so variously dislocated, conforted, and upheaved, by
mutual compression and volcanic force, leads the reflective observer, by
simple analogies, to draw a comparison between the present and an age that
has long passed. It is by a combination of actual phenomena, by an ideal
enlargement of relations in space, and of the amount of active forces, that
we are able to advance into the long sought and indefinitely anticipated
domain of geognosy, which has only within the last half century been based
on the solid foundation of scientific deduction.
It has been acutely remarked, "that notwithstanding our continual employment
of large telescopes, we are less acquainted with the exterior than with the
interior of other planets, excepting, perhaps, our own satellite." They
have been weighed, and their volume measured; and their mass and density are
becoming known with constantly-increasing exactness; thanks to the progress
made in astronomical observation and calculation. Their physical character
is, however, hidden in obscurity, for it is only in our own globe that we
can be brought in immediate contact with all the elements of organic and
inorganic creation. The diversity of the most heterogenous substances,
their admixtures and metamorphoses, and the ever-changing play of the forces
called into action, afford to the human mind both nourishment and enjoyment,
and open an immeasurable field of observation, from which the intellectual
activity of man derives a great portion of its grandeur and power. The
world of perceptive phenomena is reflected in the depths of the ideal world,
and the richness of nature and the mass of all that admits of classification
gradually become the objects of inductive reasoning.
I would here allude to the advantage, of which I have already
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spoken, possessed by that portion of physical science whose origin is
familiar to us, and is connected with our earthly existence. The physical
description of celestial bodies from the remotely-glimmering nebulae with
their suns, to the central body of our own system, is limited, as we have
seen, to general conceptions of the volume and quantity of matter. No
manifestation of vital activity is there presented to our senses. It is
only from analogies, frequently from purely ideal combinations, that we
hazard conjectures on the specific elements of matter, or on their various
modifications in the different planetary bodies. But the physical knowledge
of the heterogeneous nature of matter, its chemical differences, the regular
forms in which its molecules combine together, whether in crystals or
granules; its relations to the deflected or decomposed waves of light by
which it is penetrated; to radiating, transmitted, or polarized heat; and to
the brilliant or invisible, but not, on that account, less active phenomena
of electro-magnetism -- all this inexhaustible treasure, by which the
enjoyment of the contemplation of nature is so much heightened, is dependent
on the surface of the planet which we inhabit, and more on its solid than on
its liquid parts. I have already remarked how greatly the study of natural
objects and forces, and the infinite diversity of the sources they open for
our consideration, strengthen the mental activity, and call into action
every manifestation of intellectual progress. These relations require,
however, as little comment as that concatenation of causes by which
particular nations are permitted to enjoy a superiority over others in the
exercise of a material power derived from their command of a portion of
these elementary forces of nature.
If, on the one hand, it were necessary to indicate the difference existing
between the nature of our knowledge of the Earth and of that of the
celestial regions and their contents, I am no less desirous, on the other
hand, to draw attention to the limited boundaries of that portion of
spacefrom which we derive all our knowledge of the heterogeneous character
of matter. This has been somewhat inappropriately termed the Earth's crust;
it includes the strata most contiguous to the upper surface of our planet,
and which have been laid open before us by deep fissure-like valleys, or by
the labors of man, in the bores and shafts formed by miners. These labors*
do not extend beyond a vertical depth of somewhat more than 2000 feet (about
one third of a geographical mile) below the
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level of the sea, and consequently only about 1/9800th of the Earth's
radius.
[footnote] *In speaking of the greatest depths within the Earth reached by
human labor, we must recollect that there is a difference between the
'absolute depth' (that is to say, the depth below the Earth's surface at
that point) and the 'relative depth' (or that beneath the level of the sea).
The greatest relative depth that man has hitherto reached is probably the
bore at the new salt-works at Minden, in Prussia: in June, 1814, it was
exactly 1993 feet, the absolute depth being 2231 feet. The temperature of
the water at the bottom was 98 degrees F., which assuming the mean
temperature of the air at 49.3 degrees gives an augmentation of temperature
of 1 degree for every 54 feet. The absolute depth of the Artesian well of
Grenelle, near Paris, is only 1795 feet. According to the account of the
missionary Imbert, the fire-springs, "Ho-tsing." of the Chinese, which are
sunk to obtain [carbureted] hydrogen gas for salt-boiling, far exceed our
Artesian springs in depth. In the Chinese province of Szu-tschuan these
fire-springs are very commonly of the depth of more than 2000 feet; indeed,
at Tseu-lieu-tsing (the place of continual flow) there is a Ho-tsing which,
in the year 1812, was found to be 3197 feet deep. (Humboldt, 'Asie
Centrale', t. ii., p. 521 and 525. 'Annales de l'Association de la
Propagation de la Foi', 1829, No. 16, p. 369.)
[footnote continues] The relative depth reached at Mount Massi, in Tuscany,
south of Volterra, amounts, according to Matteuci, to only 1253 feet. The
boring at the new salt-works near Minden is probably of about the same
relative depth as the coal-mine at Apendale, near Newcastle-under-Lyme, in
Staffordshire, where men work 725 yards below the surface of the earth.
(Thomas Smith, 'Miner's Guide', 1836, p. 160.) Unfortunately, I do not know
the exact height of its mouth above the level of the sea. The relative
depth of the Monk-wearmouth mine, near Newcastle, is only 1496 feet.
(Phillips, in the 'Philos. Mag.', vol. v., 1834, p. 446.) That of the Liege
coal-mine, 'l'Esperance' at Seraing, is, according to M. Gernaert, Ingenieur
des Mines, 1223 feet in depth. The works of greatest absolute depth that
have ever been formed are for the most part situated in such elevated plains
or valleys that they either do not descend so low as the level of the sea,
or at most reach very little below it. Thus the Eselchacht, at Kuttenberg,
in Bohemia, a mine which can not now be worked, had the enormous absolute
depth of 3778 feet. (Fr. A. Schmidt, 'Berggestze der oter Mon.', abth. i.,
bd. i., s. xxxii.) Also, at St. Daniel and at Geish, on the Rorerbubel, in
the 'Landgericht' (or provincial district) of Kitzbuhl, there were, in the
sixteenth century, excavations of 3107 feet. The plans of the works of the
Rorerbubel are still preserved. (See Joseph von Sperges, 'Tyroler
Bergwerksgeschichte', s. 121. Compare, also, Humboldt, 'Gutachten uber
√∫erantreibung des Meissner Stollens in die Freiberger Erzrevier', printed
in Herder, 'uber Herantreibung des Meissner Stollens in die Freiberger
Erzrevier', printed in Herder, 'uber den jetz begonnenen Erbstollen', 1838,
s. cxxiv.) We may presume that the knowledge of the extraordinary depth of
the Rorerbuhel reached England at an early period, for I find it remarked in
Gilbert, 'de Magnete', that men have penetrated 2400 or even 3000 feet into
the crust of the Earth. ("Exigua videtur terrae portio, quae unquam
hominibus spectanda emerget aut eruitur; cum profundinus in ejus viscera,
ultra efflorescentis extremitatis corruptelam, aut propter aquas in magnis
fodin, tanquam per venas scaturientesaut propter seris salubrioris ad vitam
operariorum sustinendam necessarii defectum, aut propter ingentex sumptus ad
tantos labores exantlandos, multasque difficultates, ad profundiores terrz'
partes penetrre non possumus; adeo ut quadrigentas aut [quod rarissime]
quingentas orgyas in quibusdam metallis descendisse, stupendus omnibus
videatur connatus." -- Guilielmi Gilberti, Colcestrensis, 'de Magnete
Physiologia nova'. Lond., 1600, p. 40.)
[footnote continues] The absolute depth of the mines in the Saxon
Erzgebirge, near Freiburg, are: in the Thurmhofer mines, 1944 feet; in the
Honenbirker mines, 1827 feet; the relative depths are only 677 and 277 feet,
if, in order to calculate the elevation of the mine's mouth above the level
of the sea, we regard the elevation of Freiburg as determined by Reich's
recent observations to be 1269 feet. The absolute depth of the celebrated
mine of Joachimsthal, in Bohemia (Verkreuzung des Jung Hauer Zechen-und
Andreasganges), is full 2120 feet; so that, as Von Dechen's measurements
show that its surface is about 2388 feet above the level of the sea, it
follows that the excavations have not as yet reached that point. In the
Harz, the Samson mine at Andreasberg has an absolute depth of 2197 feet. In
what was formerly Spanish America, I know of no mine deeper than the
Valenciana, near Guanaxuato (Mexico), where I found the absolute depth of
the Planes de San Bernardo to be 1686 feet; but these planes are 5960 feet
above the level of the sea. If we compare the depth of the old Kuttenberger
mine (a depth greater than the height of our Brocken, and only 200 feet less
than that of Vesuvius) with the loftiest structures that the hands of man
have erected (with the Pyramid of Cheops and with the Cathedral of
Strasburg), we find that they stand in the ratio of eight to one. In this
note I have collected all the certain information I could find regarding the
greatest absolute and relative depths of mines and borings. In descending
eastward from Jerusalem toward the Dead Sea, a view presents itself to the
eye, which, according to our present hypsometrical knowledge of the surface
of our planet, is unrivaled in any country; as we approach the open ravine
through which the Jordan takes its course, we tread, with the open sky above
us, on rocks which, according to the barometric measurements of Berton and
Russegger are 1385 feet below the level of the Mediterranean. (Humboldt,
'Asie Centrale', th. ii., p. 323.)
The crystalline masses that have been erupted from active volcanoes, and are
generally similar to the rocks on the upper surface, have come from depths
which, although not accurately determined, must certainly be sixty times
greater than those to which human labor has been enabled to penetrate. We
are able to give in numbers the depth of the shaft where the strata of coal,
after penetrating a certain way, rise again at a distance that admits of
being accurately defined by measurements. These dips show that the
carboniferous strata, together with the fossil organic remains which they
contain, must lie, as, for instance, in Belgium, more than five or six
thousand feet* below the present level
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of the sea, and that the calcareous and the curved strata of the Devonian
basin penetrate twice that depth.
[footnote] *Basin-shaped curved strata, which dip and reappear at
measureable distances, although their deepest portions are beyond the reach
of the miner, afford sensible evidence of the nature of the earth's crust at
great depths below its surface. Testimony of this kind possesses,
consequently, a great geognostic interest. I am indebted to that excellent
geognosist, Von Dechen, for the following observations. "The depth of the
coal basin of Liege, at Mont St. Gilles, which I, in conjunction with our
friend Von Oeynhausen, have ascertained to be 3890 feet below the surface,
extends 3464 feet below the surface of the sea, for the absolute height of
Mont St. Gilles certainly does not much exceed 400 feet; the coal basin of
Mons is fully 1865 feet deeper. But all these depths are trifling compared
with those which are presented by the coal strata of Saar-Revier
(Saarbrucken). I have found after repeated examinations, that the lowest
coal stratum which is known in the neighborhood of Duttweiler, near
Bettingen, northeast of Saarlouis, must descend to depths of 20,682 and
22,015 feet (or 3.6 geographical miles) below the level of the sea." This
result exceeds, by more than 8000 feet, the assumption made in the text
regarding the basin of the Devonian strata. This coal-field is therefore
sunk as far below the surface of the sea as Chimborazo is elevated above it
-- at a depth at which the Earth's temperature must be as high as
435ºdegrees F. Hence, from the highest pinnacles of the Himalaya to the
lowest basins containing the vegetation of an earlier world, there is a
vertical distance of about 48,000 feet, or of the 435th part of the Earth's
radius.
If we compare these subterranean basins with the summits of montains that
have hitherto been considered as the most elevated portions of the raised
crust of the Earth, we obtain a distance of 37,000 feet (about seven miles),
that is, about the 1/524th of the Earth's radius. These, therefore, would
be the limits of vertical depth and of the superposition of mineral strata
to which geognostical inquiry could penetrate, even if the general elevation
of the upper surface of the earth were equal to the height of the
Dhawalagigi in the Himalaya, or of the Sorata in Bolivia. All that lies at
a greater depth below the level of the sea than the shafts or the basins of
which I have spoken, the limits to which man's labors have penetrated, or
than the depths to which the sea has in some few instances been sounded (Sir
James Ross was unable to find bottom with 27,600 feet of line), is as much
unknown to us as the interior of the other planets of our solar system. We
only know the mass of the whole Earth and its mean density by comparing it
with the open strata, which alone are accessible to us. In the interior of
the Earth, where all knowledge of its chemical and mineralogical character
fails, we are again limited to as pure conjecture, as in the remotest bodies
that revolve round the Sun. We can determine nothing with certainty
regarding the depth at which the geological strata must be supposed to be in
state of softening or of liquid fusion, of the cavities occupied by elastic
vapor, of the condition of fluids when heated under an enormous pressure, or
of the law of the increase
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of density from the upper surface to the center of the Earth.
The consideration of the increase of heat with the increase of depth toward
the interior of our planet, and of the reaction of the interior on the
external crust, leads us to the long series of volcanic phenomena. These
elastic forces are manifested in earthquakes, eruptions of gas, hot wells,
mud volcanoes and lava currents from craters of eruption and even in
producing alterations in the level of the sea.*
[footnote] * [See Daubeney 'On Volcanoes', 2d edit., 3848, p. 539, etc., on
the so called 'mud volcanoes', and the reasons advanced in favor of adopting
the term "salses" to designate these phenomena.] -- Tr.
Large plains and variously indented continents are raised or sunk, lands are
separated from seas, and the ocean itself, which is permeated by hot and
cold currents, coagulates at both poles, converting water into dense masses
of rock, which are either stratified and fixed, or broken up into floating
banks. The boundaries of sea and land, of fluids and solids, are thus
variously and frequently changed. Plains have undergone oscillatory
movements, being alternately elevated and depressed. After the elevation of
continents, mountain chains were raised upon long fissures, mostly parallel,
and in that case, probably cotemporaneous; and salt lakes and inland seas,
long inhabited by the same creatures, were forcibly separated, the fossil
remains of shells and zoophytes still giving evidence of their original
connection. Thus, in following phenomena in their mutual dependence, we are
led from the consideration of the forces acting in the interior of the Earth
to those which cause eruptions on its surface, and by the pressure of
elastic vapors give rise to burning streams of lava that flow from open
fissures.
The same powers that raised the chains of the Andes and the Hiimalaya to the
regions of perpetual snow, have occasioned new compositions and new textures
in the rocky masses, and have altered the strata which had been previously
deposited from fluids impregnated with organic substances. We here trace
the series of formations, divided and superposed according to their age, and
depending upon the changes of configuration of the surface, the dynamic
relations of upheaving forces, and the chemical action of vapors issuing
from the fissures.
The form and distribution of continents, that is to say, of that solid
portion of the Earth's surface which is suited to the luxurious development
of vegetable life, are associated by intimate connection and reciprocal
action with the encircling
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sea in which organic life is almost entirely limited to the animal world.
The liquid element is again covered by the atmosphere, an aërial ocean in
which the mountain chains and high plains of the dry land rise like shoals,
occasioning a variety of currents and changes of temperature, collecting
vapor from the region of clouds, and distributing life and motion by the
action of the streams of water which flow from their declivities.
While the geography of plants and animals depends on these intricate
relations of the distribution of sea and land, the configuration of the
surface, and the direction of isothermal lines (or zones of equal mean
annual heat), we find that the case is totally different when we consider
the human race -- the last and noblest subject in a physical description of
the globe. The characteristic differences in races, and their relative
numerical distribution over the Earth's surface, are conditions affected not
by natural relations alone, but at the same time and specially, by the
progress of civilization, and by moral and intellectual cultivation on which
depends the political superiority that distinguishes national progress.
Some few races, clinging, as it were, to the soil, are supplanted and ruined
by the dangerous vicinity of others more civilized than themselves, until
scarce a trace of their existence remains. Other races, again, not the
strongest in numbers, traverse the liquid element, and thus become the first
to acquire, although late, a geographical knowledge of at least the maritime
lands of the whole surface of our globe, from pole to pole.
I have thus, before we enter on the individual characters of that portion of
the delineation of nature which includes the sphere of telluric phenomena,
shown generally in what manner the consideration of the form of the Earth
and the incessant action of electro-magnetism and subterranean heat may
enable us to embrace in one view the relations of horizontal expansion and
elevation on the Earth's surface, the geognostic type of formations, the
domain of the ocean (of the liquid portions of the Earth), the atmosphere
with its meteorological processes, the geographical distribution of plants
and animals, and, finally, the physical gradations of the human race, which
is, exclusively and every where, susceptible of intellectual culture. This
unity of contemplation presupposes a connection of phenomena according to
their internal combination. A mere tabular arrangement of these facts would
not fulfill the object I have proposed to myself, and would not satisfy that
requirement for cosmical presentation awakened in me by the
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aspect of nature in my journeyings by sea and land, by the careful study of
forms and forces, and by a vivid impression of the unity of nature in the
midst of the most varied portions of the Earth. In the rapid advance of all
branches of physical science, much that is deficient in this attempt will,
perhaps, at no remote period, be corrected and rendered more perfect, for it
belongs to the history of the development of knowledge that portions which
have long stood isolated become gradually connected, and subject to higher
laws. I only indicate the empirical path in which I and many others of
similar pursuits with myself are advancing, full of expectation that, as
Plato tells us Socrates once desired, "Nature may be interpreted by reason
alone."*
[footnote] *Plato, 'Phaedo', p. 97. (Arist., 'Metaph.', p. 985.) compare
Hegel, 'Philosophie der Geschichte', 1840, s. 16.
The delineation of the principal characteristics of telluric phenomena must
begin with the form of our planet and its relations in space. Here too, we
may say that it is not only the mineralogical character of rocks, whether
they are crystalline, granular, or densely fossiliferous, but the
geometrical form of the Earth itself, which indicates the mode of its
origin, and is, in fact, its history. An elliptical spheroid of revolution
gives evidence of having once been a soft or fluid mass. Thus the Earth's
compression constitutes one of the most ancient geognostic events, as every
attentive reader of the book of nature can easily discern; and an analogous
fact is presented in the case of the Moon, the perpetual direction of whose
axes toward the Earth, that is to say, the increased accumulation of matter
on that half of the Moon which is turned toward us, determines the relations
of the periods of rotation and revolution, and is probably contemporaneous
with the earliest epoch in the formative history of this satellite. The
mathematical figure of the Earth is that which it would have were its
surface covered entirely by water in a state of rest; and it is this assumed
form to which all geodesical measurements of degrees refer. This
mathematical surface is different from that true physical surface which is
affected by all the accidents and inequalities of the solid parts.*
[footnote] *Bessel, 'Allgemeine Betrachtungen uber Gradmessungen nach
astronomisch-geodätischen Arbeiten', at the conclusion of Bessel and
Baeyer, 'Gradmessung in Ostpreussen', s. 427. Regarding the accumulation of
matter on the side of the Moon turned toward us (a subject noticed in an
earlier part of the text), see Laplace, 'Expos. du Syst. du Monde', p. 308.
The whole figure of the Earth is determined when we know the amount of the
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compression at the poles and the equatorial diameter; in order, however, to
obtain a perfect representation of its form it is necessary to have
measurements in two directions, perpendicular to one another.
Eleven measurements of degrees (or determinations of the curvature of the
Earth's surface in different parts), of which nine only belong to the
present century, have made us acquainted with the size of our globe, which
Pliny names "a point in the immeasurable universe."*
[footnote] *Plin., ii., 68. Seneca, 'Nat. Quaest., Praef., c. ii. "El
mundo espoco" (the Earth is small and narrow), writes Columbus from Jamaica
to Queen Isabella on the 7th of July, 1503: not because he entertained the
philosophic views of the aforesaid Romans, but because it appeared
advantageous to him to maintain that the journey from Spain was not long,
if, as he observes, "we seek the east from the west." Compare my 'Examen
Crit. de l'Hist. de la Geogr. du 15 me Siecle', t.i., p. 83, and t. ii., p.
327, where I have shown that the opinion maintained by Delisle, Freret, and
Gosselin, that the excessive differences in the statements regarding the
Earth's circumference, found in the writings of the Greeks, are only
apparent, and dependent on different values being attached to the stadia,
was put forward as early as 1495 by Jaime Ferrer, in a proposition regarding
the determination of the line of demarkation of the papal dominions.