Digitale Ausgabe

At the meeting of the Berlin Academy of Sciences, on 18thJuly 1842, a memoir by M. de Humboldt was read, of whichwe think it necessary to give a somewhat lengthened account.It is entitled “An attempt at determining the mean heightof Continents.” “Among the numerical elements on which the progress ofphysical geography appears more particularly to depend, thereis one which no attempt has been hitherto made to determine.The notion which seemed to prevail, that it was impossibleto 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 ofcountry, determined me, says M. de Humboldt, to undertake,some years ago, a work of great labour, and in appearancebarren in results, the object of which is the knowledge of themean height of continents, and the determination of the meanheight of the centre of gravity of their volume. In such a caseas this, as with many others, such as the dimensions of theglobe, 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 enumerationof 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 andhypsometrical 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 beencompleted in a very satisfactory manner in regard to centraland western Asia. “It was likewise necessary to collect, with the greatest care,astronomical determinations of the height of places, in orderto establish, to about 300 or 400 metres of absolute height,the limits between the acclivities of the mountains and theedges of the valleys. I long since demonstrated the possibi-|327| lity of such a determination of limits, and, from the comparisonwhich depends on it, I have deduced the extent of the surfaceof 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 ofthe elevated masses of Parima and Brazil, was so incorrectlylimited and circumscribed on all maps. In fact, there is ageneral tendency in all graphic representations to give themountains 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 insertedin the Memoires dé l’Académie des Sciences of Paris, on themean height of continents, and an estimate of the volumeof the elevated ridges of mountains, compared with theextent of the surface of the lower regions. An assertion ofLaplace 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 wellfrom the trigonometrical measurement of the degrees of themeridian as from the inequality of the moon, furnished aproof “that the surface of the terrestrial spheroid wouldbe nearly that of equilibrium, if that surface became fluid.Hence, and from the consideration that the sea leaves vastcontinents uncovered, we conclude that it cannot be of greatdepth, and that its mean depth is of the same order as themean height of the continents and islands above its level,a height which does not exceed 1000 metres” (or 3073Parisian feet, that is to say, only 463 feet less than the sum-mit of the Brocken, according to M. Gauss, or a little morethan the most elevated mountains of Thuringia). Laplacefurther adds, “This height is, then, a small fraction of theexcess of the radius of the equator over that of the pole, anexcess which exceeds 20,000 mètres. Just as high moun-tains cover some parts of continents, so there may be greatcavities in the bed of the sea; but it is natural to suppose|328| that their depth is less than the elevation of high mountains,as the deposits from the waves, and the remains of marineanimals, must have tended, in the lapse of time, to fill up thesegreat cavities.” Considering the profound and extensive knowledge whichthe author of the Mécanique Céleste possessed in the highestdegree, an assertion of this nature was the more striking, ashe could not be ignorant that the most elevated plateau ofFrance, that from which the extinct volcanoes of Auvergnehave risen, does not rise, according to Ramond, to more than1044 feet, and that the great Iberian plateau is not, accordingto my own measurements, more than 2100 feet above the levelof the sea. Laplace has therefore fixed the upper limit at1000 metres, merely because he has considered the extent andthe mass of the elevations of mountains to be much greater thanthey really are, inasmuch as he has confounded the height ofthe insulated peaks or culminating points with the mean heightof the mountain ridges; he has admitted much too low anumber for the depth of seas, because, in his time, data couldnot be found on the subject, and he has thence inferred theproportion of the extent of the surface (in square miles) in re-gard to all continents, to the extent of the projection of thesurfaces covered by mountains. A very exact calculation has shewn that the mass of thechain of the Andes, in South America, from where it leaves thewhole 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 dependsmuch less on those chains or longitudinal ridges of littlebreadth which traverse continents, and on their culminatingpoints or domes, which attract common observation, than onthe general configuration of the different orders of plateaux andtheir ascending series, and on those gently undulating plainswith alternating slopes, which have an influence, by their massand extent, on the position of a mean surface, that is to say, onthe height of a plain placed in such a manner that the sum ofits positive ordinates shall be equal to the sum of its negativeordinates.” |329| The comparison which Laplace has instituted in the pas-sage quoted from the Mécanique Céleste between the depth ofthe 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, asit 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, andgiving the result of the measurement of its height by Xenago-ras, Plutarch adds, “But geometricians (probably those ofAlexandria) believe that there is no mountain higher, and nosea deeper, than ten stadia.” We can entertain no doubt aboutthe exactness of the measurement made by Xenagoras; but itis 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. Herethe maximum of the heights and depths is alone taken intoaccount, and not the mean height,—a consideration whichrarely presented itself to the mind of the ancient philosophers,and which, for variable magnitudes, was applied in a usefulmanner to astronomy by the Arabs. Even in the Metereologiusof Cleomedes (i. 10), we meet with an assertion similar to thatof Plutarch; while in the Meteorologicis of the philosopher ofStagira (Arist. Met. ii. 2), the only point considered is the in-fluence of the inclination of the bottom of the sea, from eastto west, on its currents. When we try to determine the mean height of the elevationof continents above the present level of the seas, it meansthat the object is to find the centre of gravity of the volumeof these continents above that level,—an investigation very dif-ferent from that which consists in searching for the centre ofgravity of the volume of the continental mass, or the centre ofgravity of the masses, seeing that the portion which rises abovethe sea, in the crust of the globe, is by no means of the samedensity, as has been demonstrated both by geognosy and ex-periments with the pendulum. The mode of simple calculationis as follows:—Each chain of mountains is considered as a tri-angular prism placed horizontally. The mean height of thedefiles or passes, which determine the mean height of the crest|330| of the mountains, is the height of the ridge of the prism ver-tically above the surface, which constitutes the base of thechain. 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 thesurface of France contains 10,087 square geographical miles.According to M. Charpentier, the Pyrenees cover 430 of thesesquare miles; and, although the mean height of the summitsof the Pyrenees rises to 7500 feet, M. de Humboldt makes areduction upon it, on account of the erosions produced on theprism supposed to be lying horizontally, and which have tendedspecially to diminish the size of the deep transverse valleys.The effect of the Pyrenees on the whole of France is not morethan 35 metres or 108 feet; that is to say, it is to that extentthat the normal surface of the entire plain of France would beincreased, and the elevation of that surface by the comparisonof a great number of very accurate measurements at placestowards the centre (such as Bourges, Chartres, Nevers, Tours,&c.) has been found to be 480 feet. This calculation, whichM. de Humboldt has made along with M. Elie de Beaumont,furnishes the following general result, in measures thus givenby the author:—

	Toises.
1. Effect of the Pyrenees,	18
2. The French Alps, the Jura, and the Vosges, a fewtoises more than the Pyrenees; common effect,	20
3. The plateaux of Limousin, Auvergne, the Cevennes,Aveyron, Forez, Morvant, Cote d’Or; common ef-fect, nearly equal to that of the Pyrenees,	18
Now, as the normal height of the plain of France is atits maximum about	80
It follows that the mean height of France does not ex-ceed	136 toises,or 816 feet.

The Baltic, Sarmatian, and Russian plains are separatedfrom those of the north of Asia only by the meridian chainof the Oural. It is for this reason that Herodotus, who wasacquainted with the connection of the southern extremity of|331| the Oural in the country of the Issidones, called the whole ofEurope to the north of the Altai Mountains, Asia. In theneighbouring region of the Baltic plains, near the shores ofthe Baltic Sea, there are partial elevated masses which deserveparticular attention. To the west of Dantzic, between thattown and Butow, at the point where the shore of the sea ad-vances much to the north, there are many villages situated at aheight of 400 feet; the Thurmberg, moreover, the measure-ment of which has given rise to many hypsometrical contro-versies, rises, according to the trigonometrical observationsof Major Baeyer, to 1024 feet, which is perhaps the greatestelevation 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 Thurmbergof Pomerania; while, on the other hand, according to CaptainAlbrecht’s chart, the greatest depth of the Baltic Sea, betweenGothland 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 heightof which cannot be estimated at more than 60 toises, occupy,according to exact measurements, a surface nine times thatof France. The extraordinary extent of this low region isthe cause of the mean continental height of all Europe, overan extent of 17,000 square geographical miles, being 30 toisesbelow 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 generalphenomena of geology is, that the elevated masses, over ex-tensive countries, in the form of plateaux, produce an entirelydifferent effect on the elevation of the centre of gravity ofthe volume from that of chains of mountains, when they havethe same importance in breadth and in height. While thePyrenees produce scarcely the effect of a single toise on thewhole of Europe, the system of the Alps, which cover asurface almost quadruple that of the Pyrenees, has the effectof 3\( \frac{1}{2} \) toises; the Iberian peninsula, with its compact massiveplateau of 300 toises, produces the effect of 12 toises. Theplateau just named, therefore, has an effect on the whole of|332| Europe four times more considerable than the system of theAlps. This result of calculations is the more satisfactoryas it appears to be deduced without reference to any pre-vious hypothesis. We have recently acquired many new ideas respecting theconfiguration of Asia. The effect of the elevated colossalmasses of the southern portion is found to be weakened, sinceone-third of the whole continent of Asia, a portion of Siberia,which alone exceeds by a third the entire surface of Europe, doesnot 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 ofthe Icy Sea than Berlin is from the Baltic, is scarcely halfthe height of the last mentioned city. In Upper Irtysch, be-tween Buktormensy and Lake Saysan, at a point nearer theIndian than the Icy Ocean, M. de Humboldt has found thatthe plains only reached a height of about 800 feet; this, how-ever, has been called the plateau of Central Asia, and is nothalf the height of the streets of the city of Munich above thesea-level. The celebrated plateau between Lake Baikal andthe Wall of China (the stony desert of Gobi and Cha-mo),which the Russian academicians, MM. Bunge and Fuss, havemeasured with the barometer, has a mean height of only 660toises, which is nearly the same as that of the Müggelsberg atthe summit of the Brocken. There is, moreover, in the centreof this plateau, at the point where Ergi is situated (lat. 45°31′)a cauldron-shaped depression, the bottom of which descendsto 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.” Thetwo extremities of this ancient inland sea are bounded bysteep rocks, just like an ordinary sea, in the neighbourhood ofOlonbaischan and Zukeldakan. The surface of Gobi, in its masses of uniform elevation, andfrom the south-west to north-west, is twice as large as thatof all Germany, and will raise the centre of gravity of Asia|333| 20 toises; while the Himalaya and the Houen-lun, which isa 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, onleaving which the Himalaya no longer runs from east to westparallel with the Kouen-lun, but takes the direction fromsouth-east to north-west, and reunites at the projecting ridges ofTsun-ling. The altitudes of the numerous passes of Bamian,as far as the meridian of Tschamalari (24,400 feet), by whichTurner reached the Thibetian plateau of H’Lassa, are likewiseknown for an extent of 21° of longitude. The greater partof them present a very uniform height of 14,000 English feet,or 2200 toises, a height which is not of rare occurrence in thepasses 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 withoutsnow, of the height of 2428 toises, that is to say, 1400 feethigher than this pass of the Himalaya. The passes, as hasbeen stated, give the mean height of mountains. In a memoir on the relations between elevated summits orculminating 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 culminatingpoints of the Pyrenees and the Alps were in the proportion of1 to 1 \( \frac{4}{10} \). As the insulated passes of the Himalaya, for ex-ample, the Niti-Gate, by which we penetrate into the plainof the Cashmere goats, rise to the height of 2629 toises, M.de Humboldt has not admitted for the height of the Himalayanchain 14,000 English feet, but he proposes to fix it, althoughperhaps the elevation may be still too considerable, at 15,500feet, or 2432 toises. The plateau of the three Thibets ofIscardo, Ladak, and H’Lassa, is a prominence between twochains which unite with each other (the Himalaya and the|334| Kouen-Lun). Mr Vigne’s travels in Baltistan, which have justappeared, the journal of the brothers Gerard, published byLloyd, as well as the recent investigations undertaken in Indiarespecting the relative height of perpetual snow on the Indianand Thibetian declivities of the Himalaya, have demonstratedthat the mean height of the Thibetian plateaux has hithertobeen greatly exaggerated. In his work entitled “CentralAsia,” of which only a few pages of the third volume havebeen yet printed, and which will be accompanied by a hypso-metrical map of Asia from the Phasis, as far as the gulf ofPetcheli, and from the common embouchures of the Ob andthe Irtysch to the parallel of Delhi, M. de Humboldt thinksthat he has demonstrated, by bringing together a multitudeof facts, that the prominence between the Himalaya and theKouen-Lun (chains which form the southern and northernlimits of Thibet), does not rise above the mean height of 1800toises, and that it is, consequently, 200 toises lower than theplateau of Lake Titicaca. The hypsometrical configuration of the Asiatic continentis 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 thelong 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, oppositeCeylon, to the shores of the Icy Sea, in a uniform directionfrom south-south-east to north-north-west, under the name ofGhates, the Soliman chain, Paralasa, Bolor, and Oural. Thisalternating situation of auriferous meridian chains (Vigne hasrecently visited, on the eastern declivity of Bolos, in the valleyof Basha, in Baltistan, the auriferous sands mined, accordingto the Thibetians, by marmots, and, according to Herodotus,by large ants) reveals to us this law, that none of the meridianchains just named, between 64° and 75° of longitude, extendthemselves upon the adjoining ones, either towards the eastor the west, and that each of these longitudinal elevations doesnot begin to shew its extent, until a point is reached wherethe preceding has completely disappeared. 2d, Another cha-racteristic trait in the configuration of Asia, and which has|335| not been sufficiently observed, is the continuity of a consider-able elevation, east and west, between 35° and 36\( \frac{1}{2} \)° of lati-tude, from Takhialoudag, in ancient Lycia, as far as the Chineseprovince of Houpih, an elevation thrice intersected by meridianchains (Zagros, in Western Persia, Bolos, in Affghanistan, andthe chain of Assam, in the valley of Dzangho) from the westto the east of this chain, from the parallel of Dicearchus, whichis at the same time that of Rhodes, Taurus, Elbrouz, Hindou-Kho, and Kouen-Lun or A-Neoutha. In the third book of thegeography 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 twoparts. Dicearchus perceived the connection between theTaurus of Asia Minor and the snow-covered mountains ofAsia, which had acquired so much celebrity among the Greeksby the false accounts of those who had accompanied theMacedonians. Importance was assigned to the parallel ofRhodes, and to the direction of this endless chain of moun-tains. The chlamyde of Asia ought to be found further on underthis parallel (Strabo, xi. p. 519), and perhaps, says Strabo, alittle more to the east there may be another continent. TheTaurus and the plateaux of Asia Minor disclosed for the firsttime to the Greek philosophers the influence of height on tem-perature. “Even in the southern latitudes,” says the greatgeographer of Amasis, (Strabo, ii. p. 73) when the climate ofthe northern coasts of Cappadocia is compared with that of theplains of Argaios, situated 3000 stadia further south, themountains and all the elevated lands are cold, even whenthese lands consist of plains.” Strabo is the only one amongGreek authors who has made use of the word οροπεδια ormountain plain. According to the final result of the whole of M. de Hum-boldt’s investigations, the maximum assigned by Laplace forthe mean height of continents is too considerable by two-thirds.He found the following numerical elements for the threequarters of the world which have been the object of his cal-culations (Africa not yet presenting a sufficient number ofdata to be included). |336|

Europe,	105 toises	(205 metres).
North America,	117 ...	(228 ...).
South America,	177 ...	(345 ...).
Asia,	180 ...	(351 ...).

For the whole of the new continent we have 146 toises(285 metres), and for the height of the centre of gravity of thevolume of all the continental masses (Africa excepted) abovethe level of the present seas, 157.8 toises or 307 metres. Von Hoff, who has measured with extreme accuracy 1076different points, the greater part of them in the mountainousportion of Thuringia, over an extent of 224 square geographicalmiles, estimates that there are about five heights for eachsquare mile, but that these heights are unequally scattered.M. de Humboldt has asked Von Hoff, always for the purposeof verifying Laplace’s hypothesis respecting the mass of con-tinents, to calculate the mean height of the hypsometricalmeasurements which he has made. This philosopher has foundit to be 166 toises, that is to say, 8 toises more than the resultat which M. de Humboldt had arrived. We ought thence toconclude, that, since a very mountainous country of Thuringiawas measured, the number, 157 toises, or 942 feet, is a limitrather 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 whichwe are indebted to M. de Buch), we may suppose that thecentre of gravity will not always continue the same. At thesame time, considering the smallness of the masses which areraised and the weakness of the subterranean forces in action,it may be presumed, regarding such variations, that they willin a great measure compensate each other, and that the posi-tion of the centre of gravity above the ocean will not be muchchanged; but a new circumstance, which appears to resultfrom the numerical calculations of this hypsometrical labour,is, that the smallest heights in our hemisphere belong to thecontinental masses of the north. Thus Europe has furnished105 toises, North America 117 toises. The prominent cha-racter of Asia between 28° and 40° of latitude compensatesthe subtractive effect of the lower portions of Siberia. Asia|337| and South America give 180 and 177 toises. We thus read,so to speak, in these numbers, in what portions of the surfaceof our globe vulcanism, that is to say, the reaction of theinterior on the exterior, has been felt with greatest intensityin the ancient soulèvements. (L’Institut, 5th Jan. 1843 p. 4.)