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Antiqua
Antiqua; Griechisch für Fremdsprachiges; Auszeichnung: Kursivierung; Schmuck: Kapitälchen; Tabellensatz.
At the meeting of the Berlin Academy of Sciences, on
18th
July 1842, a memoir by M. de Humboldt was read, of which
we think
it necessary to give a somewhat lengthened account.
It is entitled
“An attempt at determining the mean height
of Continents.”
“Among the numerical elements on which the progress of
physical
geography appears more particularly to depend, there
is one which no attempt
has been hitherto made to determine.
The notion which seemed to prevail,
that it was impossible
to come to such a determination, has perhaps been the
prin-
cipal cause of the subject being neglected. However, the
ex-
tension of our orographical knowledge, as well as the great-
er
accuracy of the maps which represent large portions of
country, determined
me, says M. de Humboldt, to undertake,
some years ago, a work of great
labour, and in appearance
barren in results, the object of which is the
knowledge of the
mean height of continents, and the determination of the
mean
height of the centre of gravity of their
volume. In such a case
as this, as with many others, such as the
dimensions of the
globe, the probable distance of the fixed stars, the mean
tem-
perature of the poles of the earth, the thickness of the
atmo-
spheric stratum above the level of the sea, or the enumeration
of
the general population of the globe, we arrive at limitednumbers, between which the results must fall. In like
man-
ner, it is by the perfect knowledge of the geometrical
and
hypsometrical surface of a country, of France, for example,
that we
may thus be led, by analogy, to extend the conclu-
sions to a great part of
Europe and America, and are en-
abled to establish numerical data, which
have recently been
completed in a very satisfactory manner in regard to
central
and western Asia.
“It was likewise necessary to collect, with the greatest
care,
astronomical determinations of the height of places, in order
to
establish, to about 300 or 400 metres of absolute height,
the limits between
the acclivities of the mountains and the
edges of the valleys. I long since
demonstrated the possibi-
which depends on it, I
have deduced the extent of the surface
of the plains, and the horizontal and
flat portions of moun-
tains, in my geognostical researches on South
America; a por-
tion of the globe in regard to which the length of the
im-
mense wall which forms the Cordillera of the Andes, and of
the
elevated masses of Parima and Brazil, was so incorrectly
limited and
circumscribed on all maps. In fact, there is a
general tendency in all
graphic representations to give the
mountains a greater degree of breadth
than they really pos-
sess, and even in the flat portions to confound
plateaux of va-
rious kinds with each other.”
M. de Humboldt published, in 1825, two memoirs inserted
in the Memoires dé
l’Académie des Sciences of Paris, on the
mean height of continents,
and an estimate of the volume
of the elevated ridges of mountains, compared
with the
extent of the surface of the lower regions. An assertion
of
Laplace in the Mécanique Céleste (vol. v., book
xi. chap. i.
page 13), gave rise to these researches. This great
geo-
meter had established in principle, that the agreement ob-
served
between the results of experiments made with the pen-
dulum and the
compression of the earth, deduced as well
from the trigonometrical
measurement of the degrees of the
meridian as from the inequality of the
moon, furnished a
proof “that the surface of the terrestrial spheroid
would
be nearly that of equilibrium, if that surface became
fluid.
Hence, and from the consideration that the sea leaves
vast
continents uncovered, we conclude that it cannot be of great
depth,
and that its mean depth is of the same order as the
mean height of the
continents and islands above its level,
a height which does not exceed 1000
metres” (or 3073
Parisian feet, that is to say, only 463 feet less
than the sum-
mit of the Brocken, according to M. Gauss, or a little
more
than the most elevated mountains of Thuringia). Laplace
further
adds, “This height is, then, a small fraction of the
excess of the
radius of the equator over that of the pole, an
excess which exceeds 20,000
mètres. Just as high moun-
tains cover some parts of continents, so there
may be great
cavities in the bed of the sea; but it is natural to
suppose
as the deposits from the waves, and the remains
of marine
animals, must have tended, in the lapse of time, to fill up
these
great cavities.”
Considering the profound and extensive knowledge which
the author of the Mécanique Céleste possessed in the highest
degree,
an assertion of this nature was the more striking, as
he could not be
ignorant that the most elevated plateau of
France, that from which the
extinct volcanoes of Auvergne
have risen, does not rise, according to
Ramond, to more than
1044 feet, and that the great Iberian plateau is not,
according
to my own measurements, more than 2100 feet above the level
of
the sea. Laplace has therefore fixed the upper limit at
1000 metres, merely
because he has considered the extent and
the mass of the elevations of
mountains to be much greater than
they really are, inasmuch as he has
confounded the height of
the insulated peaks or culminating points with the
mean height
of the mountain ridges; he has admitted much too low
a
number for the depth of seas, because, in his time, data could
not be
found on the subject, and he has thence inferred the
proportion of the
extent of the surface (in square miles) in re-
gard to all continents, to
the extent of the projection of the
surfaces covered by mountains.
A very exact calculation has shewn that the mass of the
chain of the Andes,
in South America, from where it leaves the
whole portion of the eastern
plains of the pampas and forests,
regions whose surface is one-third larger
than that of Europe,
does not rise above 486 feet. M. de Humboldt hence
con-
cludes, “That the mean height of continental lands
depends
much less on those chains or longitudinal ridges of
little
breadth which traverse continents, and on their
culminating
points or domes, which attract common observation, than
on
the general configuration of the different orders of plateaux
and
their ascending series, and on those gently undulating plains
with
alternating slopes, which have an influence, by their mass
and extent, on
the position of a mean surface, that is to say, on
the height of a plain
placed in such a manner that the sum of
its positive ordinates shall be
equal to the sum of its negative
ordinates.”
The comparison which Laplace has instituted in the pas-
sage quoted from the
Mécanique Céleste between the depth of
the sea
and the height of continents, recalls a passage of Plu-
tarch, in the 15th
chapter of his Life of Æmilius Paulus (ed.
Reiskii, vol. ii. page
276),—a passage the more remarkable, as
it makes us acquainted with
an opinion which generally pre-
vailed among the philosophers of the
Alexandrian school.
After quoting an inscription found on Mount Olympus,
and
giving the result of the measurement of its height by Xenago-
ras,
Plutarch adds, “But geometricians (probably those of
Alexandria)
believe that there is no mountain higher, and nosea
deeper, than ten stadia.” We can entertain no doubt
about
the exactness of the measurement made by Xenagoras; but it
is
striking to observe, that the philosophers of this school esta-
blished in
the structure of the earth a perfect equality be-
tween the heights or
positive and negative ordinates. Here
the maximum of the heights and depths
is alone taken into
account, and not the mean height,—a consideration
which
rarely presented itself to the mind of the ancient
philosophers,
and which, for variable magnitudes, was applied in a
useful
manner to astronomy by the Arabs. Even in the Metereologius
of Cleomedes (i. 10), we meet with an assertion
similar to that
of Plutarch; while in the Meteorologicis of the philosopher of
Stagira (Arist. Met. ii. 2),
the only point considered is the in-
fluence of the inclination of the
bottom of the sea, from east
to west, on its currents.
When we try to determine the mean height of the elevation
of continents above
the present level of the seas, it means
that the object is to find the
centre of gravity of the volume
of these continents above that
level,—an investigation very dif-
ferent from that which consists in
searching for the centre of
gravity of the volume of the continental mass,
or the centre of
gravity of the masses, seeing that the portion which rises
above
the sea, in the crust of the globe, is by no means of the
same
density, as has been demonstrated both by geognosy and
ex-
periments with the pendulum. The mode of simple calculation
is as
follows:—Each chain of mountains is considered as a tri-
angular
prism placed horizontally. The mean height of the
defiles or passes, which
determine the mean height of the crest
tically above the
surface, which constitutes the base of the
chain. The plateaux are
calculated as straight prisms, in or-
der to establish their solidity.
For the purpose of giving an example, taken from Europe,
of this kind of
calculation, M. de Humboldt states, that the
surface of France contains
10,087 square geographical miles.
According to M. Charpentier, the Pyrenees
cover 430 of these
square miles; and, although the mean height of the
summits
of the Pyrenees rises to 7500 feet, M. de Humboldt makes
a
reduction upon it, on account of the erosions produced on the
prism
supposed to be lying horizontally, and which have tended
specially to
diminish the size of the deep transverse valleys.
The effect of the Pyrenees
on the whole of France is not more
than 35 metres or 108 feet; that is to
say, it is to that extent
that the normal surface of the entire plain of
France would be
increased, and the elevation of that surface by the
comparison
of a great number of very accurate measurements at
places
towards the centre (such as Bourges, Chartres, Nevers,
Tours,
&c.) has been found to be 480 feet. This calculation,
which
M. de Humboldt has made along with M. Elie de Beaumont,
furnishes
the following general result, in measures thus given
by the
author:—
The Baltic, Sarmatian, and Russian plains are separated
from those of the
north of Asia only by the meridian chain
of the Oural. It is for this reason
that Herodotus, who was
acquainted with the connection of the southern
extremity of
Europe to the north of the Altai Mountains,
Asia. In the
neighbouring region of the Baltic plains, near the shores
of
the Baltic Sea, there are partial elevated masses which
deserve
particular attention. To the west of Dantzic, between that
town
and Butow, at the point where the shore of the sea ad-
vances much to the
north, there are many villages situated at a
height of 400 feet; the
Thurmberg, moreover, the measure-
ment of which has given rise to many
hypsometrical contro-
versies, rises, according to the trigonometrical
observations
of Major Baeyer, to 1024 feet, which is perhaps the
greatest
elevation to be found between the Harz and Oural. It is
sur-
prising that, according to the measurements made by M.
Struve of
the culminating point of Livonia, the Munamaggi,
this mountain rises only 4
toises higher than the Thurmberg
of Pomerania; while, on the other hand,
according to Captain
Albrecht’s chart, the greatest depth of the
Baltic Sea, between
Gothland and Windau, is not more than 167 toises, a
mea-
surement almost identical with that of the Thurmberg.
The flat countries exclusively European, the normal height
of which cannot be
estimated at more than 60 toises, occupy,
according to exact measurements, a
surface nine times that
of France. The extraordinary extent of this low
region is
the cause of the mean continental height of all Europe,
over
an extent of 17,000 square geographical miles, being 30
toises
below the result we have found for France. As to the rest,
not to
occupy more time with numbers, M. de Humboldt adds,
that an important
consideration in the study of the general
phenomena of geology is, that the
elevated masses, over ex-
tensive countries, in the form of plateaux,
produce an entirely
different effect on the elevation of the centre of
gravity of
the volume from that of chains of mountains, when they
have
the same importance in breadth and in height. While the
Pyrenees
produce scarcely the effect of a single toise on the
whole of Europe, the
system of the Alps, which cover a
surface almost quadruple that of the
Pyrenees, has the effect
of 3
plateau of 300 toises, produces the effect of 12 toises.
The
plateau just named, therefore, has an effect on the whole of
Alps. This result of calculations is the more satisfactory
as it
appears to be deduced without reference to any pre-
vious hypothesis.
We have recently acquired many new ideas respecting the
configuration of
Asia. The effect of the elevated colossal
masses of the southern portion is
found to be weakened, since
one-third of the whole continent of Asia, a
portion of Siberia,
which alone exceeds by a third the entire surface of
Europe, does
not reach a normal height of 40 toises. This is,
likewise,
the height of Orenbourg, on the northern shore of the
Cas-
pian Sea. Tobolsk does not attain the half of this height,
and
Casan, which is five times more distant from the shore of
the Icy Sea than
Berlin is from the Baltic, is scarcely half
the height of the last mentioned
city. In Upper Irtysch, be-
tween Buktormensy and Lake Saysan, at a point
nearer the
Indian than the Icy Ocean, M. de Humboldt has found that
the
plains only reached a height of about 800 feet; this, how-
ever, has been
called the plateau of Central Asia, and is not
half the height of the
streets of the city of Munich above the
sea-level. The celebrated plateau
between Lake Baikal and
the Wall of China (the stony desert of Gobi and
Cha-mo),
which the Russian academicians, MM. Bunge and Fuss,
have
measured with the barometer, has a mean height of only 660
toises,
which is nearly the same as that of the Müggelsberg at
the summit of the
Brocken. There is, moreover, in the centre
of this plateau, at the point
where Ergi is situated (lat. 45°31′)
a cauldron-shaped depression,
the bottom of which descends
to 400 toises, that is to say, the height of
Madrid. “This de-
pression,” says M. Bunge, in a memoir not
yet published,
“is covered with Halophytes and species of the genus
Arundo,
and, according to the tradition of the
Mongolians who ac-
companied us, it was formerly a great inland sea.”
The
two extremities of this ancient inland sea are bounded by
steep
rocks, just like an ordinary sea, in the neighbourhood of
Olonbaischan and
Zukeldakan.
The surface of Gobi, in its masses of uniform elevation, and
from the
south-west to north-west, is twice as large as that
of all Germany, and will
raise the centre of gravity of Asia
a prolongation of the
Hindoo-Kho, with the plateaux of Thibet,
which connect the Himalaya with the
Kouen-lun, will only pro-
duce an effect of 56 toises. In the examination of
the consi-
derable relief between the plains of the Indus and the
de-
pressed plateau of Tarim, which, on leaving Kaschgar, in-
clines to
the east towards Lake Lop, it is necessary to exa-
mine with more care the
point near the meridian of Kaylasa,
and the two sacred lakes of Manasa and
Ravana-Brada, on
leaving which the Himalaya no longer runs from east to
west
parallel with the Kouen-lun, but takes the direction
from
south-east to north-west, and reunites at the projecting ridges
of
Tsun-ling. The altitudes of the numerous passes of Bamian,
as far as
the meridian of Tschamalari (24,400 feet), by which
Turner reached the
Thibetian plateau of H’Lassa, are likewise
known for an extent of 21°
of longitude. The greater part
of them present a very uniform height of
14,000 English feet,
or 2200 toises, a height which is not of rare
occurrence in the
passes of the chain of the Andes. The great route which
M.
de Humboldt followed from Quito, on his way to Cuença,
was,
for example, at Assuay (Ladera de Cadlud), and without
snow, of the height
of 2428 toises, that is to say, 1400 feet
higher than this pass of the
Himalaya. The passes, as has
been stated, give the mean height of
mountains.
In a memoir on the relations between elevated summits or
culminating points,
and the height of mountain chains, M.
de Humboldt has demonstrated that the
chain of the Pyre-
nees, calculated from twenty-three passes, was 50 toises
high-
er than the mean chain of the Alps, although the
culminating
points of the Pyrenees and the Alps were in the proportion
of
1 to 1
ample, the Niti-Gate, by which we penetrate
into the plain
of the Cashmere goats, rise to the height of 2629 toises,
M.
de Humboldt has not admitted for the height of the Himalayan
chain
14,000 English feet, but he proposes to fix it, although
perhaps the
elevation may be still too considerable, at 15,500
feet, or 2432 toises. The
plateau of the three Thibets of
Iscardo, Ladak, and H’Lassa, is a
prominence between two
chains which unite with each other (the Himalaya and
the
appeared, the journal of the brothers Gerard,
published by
Lloyd, as well as the recent investigations undertaken in
India
respecting the relative height of perpetual snow on the Indian
and
Thibetian declivities of the Himalaya, have demonstrated
that the mean
height of the Thibetian plateaux has hitherto
been greatly exaggerated. In
his work entitled “Central
Asia,” of which only a few pages of
the third volume have
been yet printed, and which will be accompanied by a
hypso-
metrical map of Asia from the Phasis, as far as the gulf
of
Petcheli, and from the common embouchures of the Ob and
the Irtysch
to the parallel of Delhi, M. de Humboldt thinks
that he has demonstrated, by
bringing together a multitude
of facts, that the prominence between the
Himalaya and the
Kouen-Lun (chains which form the southern and
northern
limits of Thibet), does not rise above the mean height of
1800
toises, and that it is, consequently, 200 toises lower than
the
plateau of Lake Titicaca.
The hypsometrical configuration of the Asiatic continent
is perhaps still
more remarkable for its plains and depres-
sions, than for its colossal
heights. This continent is distin-
guished by two principal characteristic
features; 1st, by the
long series of meridian chains, which, with parallel
axes,
but alternating with each other (having perhaps been pro-
jected
comme des filons) extend from Lake Comorin,
opposite
Ceylon, to the shores of the Icy Sea, in a uniform
direction
from south-south-east to north-north-west, under the name
of
Ghates, the Soliman chain, Paralasa, Bolor, and Oural.
This
alternating situation of auriferous meridian chains (Vigne
has
recently visited, on the eastern declivity of Bolos, in the
valley
of Basha, in Baltistan, the auriferous sands mined, according
to
the Thibetians, by marmots, and, according to Herodotus,
by large ants)
reveals to us this law, that none of the meridian
chains just named, between
64° and 75° of longitude, extend
themselves upon the adjoining ones, either
towards the east
or the west, and that each of these longitudinal elevations
does
not begin to shew its extent, until a point is reached where
the
preceding has completely disappeared. 2d, Another cha-
racteristic trait in
the configuration of Asia, and which has
able elevation,
east and west, between 35° and 36
tude, from Takhialoudag,
in ancient Lycia, as far as the Chinese
province of Houpih, an elevation
thrice intersected by meridian
chains (Zagros, in Western Persia, Bolos, in
Affghanistan, and
the chain of Assam, in the valley of Dzangho) from the
west
to the east of this chain, from the parallel of Dicearchus,
which
is at the same time that of Rhodes, Taurus, Elbrouz, Hindou-
Kho,
and Kouen-Lun or A-Neoutha. In the third book of the
geography of
Eratosthenés, we find the first germ of the no-
tion of a chain of mountains
(Strabo, xv. p. 689, Cas.) run-
ning in a continuous manner, and dividing
Asia into two
parts. Dicearchus perceived the connection between
the
Taurus of Asia Minor and the snow-covered mountains of
Asia, which
had acquired so much celebrity among the Greeks
by the false accounts of
those who had accompanied the
Macedonians. Importance was assigned to the
parallel of
Rhodes, and to the direction of this endless chain of
moun-
tains. The chlamyde of Asia ought to be found further on
under
this parallel (Strabo, xi. p. 519), and perhaps, says Strabo,
a
little more to the east there may be another continent. The
Taurus and
the plateaux of Asia Minor disclosed for the first
time to the Greek
philosophers the influence of height on tem-
perature. “Even in the
southern latitudes,” says the great
geographer of Amasis, (Strabo,
ii. p. 73) when the climate of
the northern coasts of Cappadocia is compared
with that of the
plains of Argaios, situated 3000 stadia further south,
the
mountains and all the elevated lands are cold, even when
these lands
consist of plains.” Strabo is the only one among
Greek authors who
has made use of the word
οροπεδια or
mountain
plain.
According to the final result of the whole of M. de Hum-
boldt’s
investigations, the maximum assigned by Laplace for
the mean height of
continents is too considerable by two-thirds.
He found the following
numerical elements for the three
quarters of the world which have been the
object of his cal-
culations (Africa not yet presenting a sufficient number
of
data to be included).
For the whole of the new continent we have 146 toises
(285 metres), and for
the height of the centre of gravity of the
volume of all the continental
masses (Africa excepted) above
the level of the present seas, 157.8 toises
or 307 metres.
Von Hoff, who has measured with extreme accuracy 1076
different points, the
greater part of them in the mountainous
portion of Thuringia, over an extent
of 224 square geographical
miles, estimates that there are about five
heights for each
square mile, but that these heights are unequally
scattered.
M. de Humboldt has asked Von Hoff, always for the purpose
of
verifying Laplace’s hypothesis respecting the mass of con-
tinents,
to calculate the mean height of the hypsometrical
measurements which he has
made. This philosopher has found
it to be 166 toises, that is to say, 8
toises more than the result
at which M. de Humboldt had arrived. We ought
thence to
conclude, that, since a very mountainous country of
Thuringia
was measured, the number, 157 toises, or 942 feet, is a
limit
rather too high than too low.
In the certainty in which we now are respecting the pro-
gressive and partial
rising of Sweden (one of the most im-
portant facts in physical geography,
for a knowledge of which
we are indebted to M. de Buch), we may suppose that
the
centre of gravity will not always continue the same. At the
same
time, considering the smallness of the masses which are
raised and the
weakness of the subterranean forces in action,
it may be presumed, regarding
such variations, that they will
in a great measure compensate each other,
and that the posi-
tion of the centre of gravity above the ocean will not be
much
changed; but a new circumstance, which appears to result
from the
numerical calculations of this hypsometrical labour,
is, that the smallest
heights in our hemisphere belong to the
continental masses of the north.
Thus Europe has furnished
105 toises, North America 117 toises. The
prominent cha-
racter of Asia between 28° and 40° of latitude
compensates
the subtractive effect of the lower portions of Siberia.
Asia
so to speak, in these numbers, in what portions of the
surface
of our globe vulcanism, that is to say, the reaction of
the
interior on the exterior, has been felt with greatest intensity
in
the ancient soulèvements. (L’Institut,