Alexander von Humboldt
Between 1799 and 1804, Humboldt travelled to Latin America, exploring and describing it from a scientific point of view for the first time. His description of the journey was written up and published in an enormous set of volumes over 21 years. He was one of the first to propose that the lands bordering the Atlantic were once joined (South America and Africa in particular). Later, his five-volume work Kosmos (1845) attempted to unify the various branches of scientific knowledge. Humboldt supported and worked with other scientists, including Joseph-Louis Gay-Lussac, Justus von Liebig, Louis Agassiz, Matthew Fontaine Maury, and most notably Aime Bonpland (with whom he conducted much of his scientific exploration).

# Humboldt's life and travels

## Early life and education
Humboldt was born in Berlin in the Margraviate of Brandenburg. His father, Alexander George von Humboldt, was a major in the Prussian Army and belonged to a prominent Pomeranian family and was rewarded for his services during the Seven Years' War with the post of Royal Chamberlain. He married Maria Elizabeth von Colomb in 1766, the widow of Baron von Holwede, and they had two sons.
Alexander's childhood was not promising as regards either health or intellect. His characteristic tastes, however, soon displayed themselves; and from his penchant for collecting and labelling plants, shells, and insects he received the playful title of "the little apothecary". His father died in 1779, after which his mother took care of his education. Destined for a political career, he studied finance during six months at the University of Frankfurt (Oder); and a year later, on April 25, 1789, he matriculated at Gottingen, then eminent for the lectures of C. G. Heyne and J. F. Blumenbach. His vast and varied powers were by this time fully developed, and during a vacation in 1789, he made a scientific excursion up the Rhine, and produced the treatise Mineralogische Beobachtungen uber einige Basalte am Rhein (Brunswick, 1790).
Humboldt's passion for travel was confirmed by friendships formed at Gottingen with Georg Forster, Heyne's son-in-law, the distinguished companion of Captain James Cook on his second voyage. Henceforth his studies and rare combination of personal talents became directed with extraordinary insight and perseverance to the purpose of preparing himself for a distinctive calling as a scientific explorer. With this view he studied commerce and foreign languages at Hamburg, geology at Technische Universitat Bergakademie Freiberg under A. G. Werner, anatomy at Jena under J. C. Loder, and astronomy and the use of scientific instruments under F. X. von Zach and J. G. Kohler. His researches into the vegetation of the mines of Freiberg led to the publication, in 1793, of his Florae Fribergensis Specimen; and the results of a prolonged course of experiments on the phenomena of muscular irritability, then recently discovered by Luigi Galvani, were contained in his Versuche uber die gereizte Muskel- und Nervenfaser (Berlin, 1797), enriched in the French translation with notes by Blumenbach.

## Travels and work in Europe
In 1794 Humboldt was admitted to the intimacy of the famous Weimar coterie, and contributed (June,7 1795) to Schiller's new periodical, Die Horen, a philosophical allegory entitled Die Lebenskraft, oder der rhodische Genius. In the summer of 1790 he paid a short visit to England in company with Forster. In 1792 and 1797 he was in Vienna; in 1795 he made a geological and botanical tour through Switzerland and Italy. He had obtained in the meantime official employment: appointed assessor of mines at Berlin, February 29, 1792. Although this service to the state was regarded by him as only an apprenticeship to the service of science, he fulfilled its duties with such conspicuous ability that not only did he rise rapidly to the highest post in his department, but he was also entrusted with several important diplomatic missions. The death of his mother, on 19 November 1796, set him free to follow the bent of his genius, and severing his official connections, he waited for an opportunity to fulfil his long-cherished dream of travel.

## Latin American expedition
On the postponement of Captain Baudin's proposed voyage of circumnavigation, which he had been officially invited to accompany, Humboldt left Paris for Marseille with Aime Bonpland, the designated botanist of the frustrated expedition, hoping to join Napoleon Bonaparte in Egypt. Means of transport, however, were not forthcoming, and the two travellers eventually found their way to Madrid, where the unexpected patronage of the minister Don Mariano Luis de Urquijo convinced them to make Spanish America the scene of their explorations.
Armed with powerful recommendations, they sailed in the Pizarro from A Coruna, on June 5 1799, stopped six days on the island of Tenerife to climb Mount Teide, and landed at Cumana, Venezuela, on 16 July. Humboldt visited the mission at Caripe where he found the oil-bird, which he was to make known to science as Steatornis caripensis. Returning to Cumana, Humboldt observed, on the night of 11-12 November, a remarkable meteor shower (the Leonids), thus forming the starting-point of our acquaintance with the periodicity of the phenomenon. He proceeded with Bonpland to Caracas; and in February 1800 they left the coast with the purpose of exploring the course of the Orinoco River. This trip, which lasted four months, and covered 1725 miles of wild and largely uninhabited country, had the important result of establishing the existence of a communication between the water-systems of the rivers Orinoco and Amazon, and of determining the exact position of the bifurcation. Around March 19, 1800, von Humboldt and Bonpland discovered and captured some electric eels. They both received potentially dangerous electric shocks during their investigations.
On November 24, the two friends set sail for Cuba, and after a stay of some months they regained the mainland at Cartagena, Colombia. Ascending the swollen stream of the Magdalena, and crossing the frozen ridges of the Cordillera Real, they reached Quito on January 6 1802, after a tedious and difficult journey. Their stay there was marked by the ascent of Pichincha and Chimborazo. Humboldt and his party reached an altitude of 19,286 feet, a world record at the time. The journey concluded with an expedition to the sources of the Amazon en route for Lima, Peru. At Callao, Humboldt observed the transit of Mercury on November 9, and studied the fertilizing properties of guano, the subsequent introduction of which into Europe was due mainly to his writings. A tempestuous sea-voyage brought them to Mexico, where they resided for a year, travelling to different cities. This was followed by a short visit to the United States of America, after which they set sail for Europe from the mouth of the Delaware, and landed at Bordeaux on August 3, 1804.

## Achievements of the Latin American expedition
This memorable expedition may be regarded as having laid the foundation of the sciences of physical geography and meteorology. By his delineation (in 1817) of "isothermal lines", he at once suggested the idea and devised the means of comparing the climatic conditions of various countries. He first investigated the rate of decrease in mean temperature with the increase in elevation above sea level, and afforded, by his inquiries regarding the origin of tropical storms, the earliest clue to the detection of the more complicated law governing atmospheric disturbances in higher latitudes; while his essay on the geography of plants was based on the then novel idea of studying the distribution of organic life as affected by varying physical conditions. His discovery of the decrease in intensity of Earth's magnetic field from the poles to the equator was communicated to the Paris Institute in a memoir read by him on 7 December 1804, and its importance was attested by the speedy emergence of rival claims. His services to geology were based mainly on his attentive study of the volcanoes of the New World. He showed that they fell naturally into linear groups, presumably corresponding with vast subterranean fissures; and by his demonstration of the igneous origin of rocks previously held to be of aqueous formation, he contributed largely to the elimination of erroneous views, such as Neptunism.
The reduction into form and publication of the encyclopdic mass of scientific, political and archaeological material  collected by him during his absence from Europe  was now Humboldt's most urgent desire. After a short trip to Italy with Gay-Lussac for the purpose of investigating the law of magnetic declination, and a sojourn of two and a half years in his native city, he finally, in the spring of 1808, settled in Paris with the purpose of securing the scientific cooperation required for bringing his great work through the press. This colossal task, which he at first hoped would occupy but two years, eventually cost him twenty-one, and even then it remained incomplete. In these early years in Paris, he shared accommodation and a laboratory with his former rival, and now friend, Joseph-Louis Gay-Lussac, both working together on the analysis of gases and the composition of the atmosphere.
Humboldt is considered to be the be the "second discoverer of Cuba" due to all the scientific and social research he conducted on this Spanish colony. During an initial three month stay at Havana his first tasks were to properly measure Havana city and nearby towns of Guanabacoa, Regla and Bejucal.
He befriended Cuban land owner and thinker Francisco Arrango y Parreno, together they visited the Guines area in south Havana, the valleys of Matanzas Province and the Valley of the Sugar Mills in Trinidad, these three were at the time the first frontier of the sugar production in the island, during these trips Humboldt collected statistical information on Cuba's population, production, technology and trade, and with Arrango he made contributions and ideas to enhance them. He predicted that the agricultural and commercial potential of Cuba was huge and could be vastly improved with a proper leadership in the future. After traveling America, Humboldt returned to Cuba for a second shorter stay in April 1804. During this time he conducted among his scientific and landlords friends mineralogical surveys and finished his vast Botanical and Fauna collection on the Island.
Finally, Humboldt conducted a rudimentary census of the indigenous and European inhabitants in New Spain, and on May 5, 1804, he estimated the population to be six million individuals.

## Humboldt acclaimed
With the exception of Napoleon Bonaparte, Humboldt was now the most famous man in Europe. The acclaimed American painter Rembrandt Peale painted him during his stay between 1808 and 1810 as one of the most prominent figures in Europe at the time. A chorus of applause greeted him from every side. Academies, both native and foreign, were eager to enrol him among their members. King Frederick William III of Prussia conferred upon him the honour, without exacting the duties, attached to the post of royal chamberlain, together with a pension of 2,500 thalers, afterwards doubled. He refused the appointment of Prussian minister of public instruction in 1810. In 1814 he accompanied the allied sovereigns to London. Three years later he was summoned by the king of Prussia to attend him at the congress of Aachen. Again in the autumn of 1822 he accompanied the same monarch to the congress of Verona, proceeded thence with the royal party to Rome and Naples, and returned to Paris in the spring of 1823.
Humboldt had long regarded the French capital as his true home. There he found, not only scientific sympathy, but the social stimulus which his vigorous and healthy mind eagerly craved. He was equally in his element as the lion of the salons and as the savant of the institute and the observatory. During that time he met in 1818 the young and brilliant Peruvian student of the Royal Mining School of Paris, Mariano Eduardo de Rivero y Ustariz. They became good friends. Subsequently von Humboldt acted as a mentor of the career of this promising Peruvian scientist. Thus, when at last he received from his sovereign a summons to join his court at Berlin, he obeyed indeed, but with deep and lasting regret. The provincialism of his native city was odious to him. He never ceased to rail against the bigotry without religion, aestheticism without culture, and philosophy without common sense, which he found dominant on the banks of the Spree. The unremitting benefits and sincere attachment of two well-meaning princes secured his gratitude, but could not appease his discontent. At first he sought relief from the "nebulous atmosphere" of his new abode by frequent visits to Paris; but as years advanced his excursions were reduced to accompanying the monotonous "oscillations" of the court between Potsdam and Berlin. On 12 May 1827 he settled permanently in the Prussian capital, where his first efforts were directed towards the furtherance of the science of terrestrial magnetism. For many years it had been one of his favourite schemes to secure, by means of simultaneous observations at distant points, a thorough investigation of the nature and law of "magnetic storms" a term invented by him to designate abnormal disturbances of Earth's magnetism. The meeting at Berlin, on 18 September 1828, of a newly-formed scientific association, of which he was elected president, gave him the opportunity of setting on foot an extensive system of research in combination with his diligent personal observations. His appeal to the Russian government in 1829 led to the establishment of a line of magnetic and meteorological stations across northern Asia; while his letter to the Duke of Sussex, then (April 1836) president of the Royal Society, secured for the undertaking the wide basis of the British dominions.
The Encyclopdia Britannica, Eleventh Edition, observes, "Thus that scientific conspiracy of nations which is one of the noblest fruits of modern civilization was by his exertions first successfully organized." However, earlier examples of international scientific cooperation exist, notably the eighteenth-century observations of the Transits of Venus.

## Explorations in Russia
In 1811, and again in 1818, projects of Asiatic exploration were proposed to Humboldt, first by the Russian government, and afterwards by the Prussian government; but on each occasion, untoward circumstances interposed, and it was not until he had begun his sixtieth year that he resumed his early role of traveller in the interests of science. Between May and November 1829, he, together with his chosen associates, Gustav Rose and C. G. Ehrenberg, traversed the wide expanse of the Russian empire from the Neva to the Yenesei, accomplishing in twenty-five weeks a distance of 9,614 miles. The journey, however, though carried out with all the advantages afforded by the immediate patronage of the Russian government, was too rapid to be profitable. Its most important fruits were crabapples, the correction of the prevalent exaggerated estimate of the height of the Central Asian plateau, and the discovery of diamonds in the gold-washings of the Ural, a result which Humboldt's Brazilian experiences enabled him to predict, and by predicting to secure.

## Humboldt as diplomat
Between 1830 and 1848 von Humboldt was frequently employed in diplomatic missions to the court of Louis Philippe, with whom he always maintained the most cordial personal relations.
His brother, Wilhelm von Humboldt, died in Alexander's arms on 8 April 1836. The death saddened the later years of his life; Alexander lamented that he had lost half of himself with the death of his brother.
Upon the accession of the crown prince Frederick William IV in June 1840, Humboldt's favour at court increased. Indeed, the new king's craving for Humboldt's company became at times so importunate as to leave him only a few waking hours to work on his writing.

## The "Cosmos"
It is not often that a man postpones until his seventy-sixth year, and then successfully executes, the crowning task of his life. Yet this was Humboldt's case. The first two volumes of the Kosmos were published, and, in the main, composed, between the years 1845 and 1847. The idea of a work that should convey not only a graphic description, but an imaginative conception of the physical world which should support generalization by details, and dignify details by generalization, had floated before his mind for more than half a century. It first took definite shape in a set of lectures delivered by him before the University of Berlin in the winter of 1827-28. These lectures formed, as his latest biographer expresses it, "the cartoon for the great fresco of the Kosmos." The scope of this remarkable work may be described briefly as the representation of the unity amidst the complexity of nature. In it, the large and vague ideals of the 18th century are sought to be combined with the exact scientific requirements of the 19th century. And, in spite of inevitable shortcomings, the attempt was in an eminent degree successful. A certain heaviness of style, too, and laborious picturesqueness of treatment make it more imposing than attractive to the general reader. But its supreme and abiding value consists in its faithful reflection of the mind of a great man. No higher eulogy can be passed on Humboldt than that, in attempting, and not unworthily so, to portray the universe, he succeeded still more perfectly in portraying his own comprehensive intelligence.
The last decade of his long life  his "improbable" years, as he was accustomed to calling them  was devoted to the continuation of this work, of which the third and fourth volumes were published in 1850-58, while a fragment of a fifth was to appear posthumously in 1862. In these volumes he sought to elaborate upon the individual branches of science broadly surveyed in the first volume. Notwithstanding their high separate value, it must be admitted that, from an artistic point of view, these additions were deformities. 
The characteristic idea of the work, so far as such a gigantic idea admitted of literary incorporation, was completely developed in its opening portions, and the attempt to convert it into a scientific encyclopdia was in truth to nullify its generating motive. Humboldt's remarkable industry and accuracy were never more conspicuous than in this latest trophy to his genius. Nor did he rely entirely on his own labours. 
He owed much of what he accomplished to his rare power of assimilating thoughts that were not as his own and availing himself of others' cooperation. The notes to Kosmos overflow with laudatory citations, the current coin in which he discharged his intellectual debts.

## Illness and death
On February 24, 1857 Humboldt suffered a minor stroke, which passed without perceptible symptoms. It was not until the winter of 1858-1859 that his strength began to decline, and that spring, on 6 May, he died quietly in Berlin at the age of 89. The honours which had been showered on him during life continued after his death. His remains, prior to being interred in the family resting-place at Tegel, were conveyed in state through the streets of Berlin, and received by the prince-regent at the door of the cathedral. The first centenary of his birth was celebrated on 14 September, 1869, with great enthusiasm in both the New and Old Worlds. Numerous monuments erected in his honour, and newly explored regions named after Humboldt, bear witness to his wide fame and popularity.

## Personal life
Much of Humboldt's private life remains a mystery because he destroyed his private letters.
In 1908 the sexual researcher Paul Nacke, who worked with Magnus Hirschfeld, gathered reminiscences of him from people who recalled his participation in the homosexual subculture of Berlin. A travelling companion, the pious Francisco Jose de Caldas, accused him of frequenting houses where 'impure love reigned', of making friends with 'obscene dissolute youths', and giving vent to 'shameful passions of his heart'.
Throughout his life Humboldt formed strong emotional attachments to men. To the soldier Reinhard von Haeften he wrote: "I know that I live only through you, my good precious Reinhard, and that I can only be happy in your presence." He never married, yet there were two notable exceptions where he seemed to have been drawn to the opposite sex. The first was an adolescent infatuation with Henriette Herz, the beautiful wife of Marcus Herz, his mentor, and the second was a short lived but intimate relationship with a woman named Pauline Wiesel in 1808 Paris. He was strongly attached to his brother's family; and in his later years the somewhat arbitrary sway of an old and faithful servant held him in more than matrimonial bondage. By a singular example of generosity (or some people would say weakness), he executed, four years before his death, a deed of gift transferring to this man Seifert the absolute possession of his entire property. No undue advantage appears to have been taken of this extraordinary concession.
The clue to his inner life might well be found in a certain egotism of self-culture scarcely separable from the promptings of genius. Yet his attachments, once formed, were sincere and lasting. He made innumerable friends; and it does not stand on record that he ever lost one. His benevolence was throughout his life active and disinterested. His early zeal for the improvement of the condition of the miners in Galicia and Franconia, his consistent detestation of slavery, his earnest patronage of rising men of science, bear witness to the large humanity which formed the ground-work of his character.
The faults of his old age have been brought into undue prominence by the injudicious publication of his letters to Varnhagen von Ense. The chief of these was his habit of smooth speaking, almost amounting to flattery, which formed a painful contrast with the caustic sarcasm of his confidential utterances. His vanity, at all times conspicuous, was tempered by his sense of humour, and was so frankly avowed as to invite sympathy rather than provoke ridicule. After every deduction has been made, he yet stands before us as a colossal figure, not unworthy to take his place beside Goethe as the representative of the scientific side of the culture of his country.

# Honours and namesakes

## Species named after Humboldt
As a consequence of his explorations, von Humboldt described many geographical features and species of life that were hitherto unknown to Europeans. Species named after him include:
- Spheniscus humboldti  Humboldt penguin
- Dosidicus gigas  Humboldt squid
- Lilium humboldtii  Humboldt's lily
- Phragmipedium humboldtii  an orchid
- Quercus humboldtii  South American oak
- Conepatus humboldtii  Humboldt's Hog-nosed skunk
- Annona humboldtii  Neotropical tree or shrub
- Annona humboldtiana  Neotropical tree or shrub
- Utricularia humboldtii  a bladderwort
- Geranium humboldtii  a cranesbill
- Salix humboldtiana  a South-American willow. 
- Inia geoffrensis humboldtiana  Amazon River Dolphin subspecies living at Orinoco River basin

## Geographical Features named after Humboldt
Features named after him include the following:
- Humboldt Bay  Bay in Northern California
- Humboldt Current  off the west coast of South America
- Humboldt River
- Humboldt Sink
- East and West Humboldt Range.
- Venezuela's first-designated national monument (the "Monumento Nacional Alejandro de Humboldt") at Caripe.

## Places named after Humboldt
The following places are named for Humboldt:
- Humboldt, South Dakota, United States
- Humboldt, Nebraska, United States
- Humboldt, Tennessee, United States
- Humboldt, Kansas, United States
- Humboldt County, California, United States
- Humboldt County, Nevada, United States
- Humboldt County, Iowa, United States
- Humboldt, Saskatchewan, Canada
- Humboldt Junior High School, Saint Paul, MN, United States
- Humboldt Senior High School, Saint Paul, MN, United States
- ((Colegio Aleman Alexander von Humboldt, Mexico City Mexico.
- Humboldt Park: an official Community Area and park in Chicago, Illinois, United States
- Humboldt Peak (Pico Humboldt) Merida State, Venezuela
- Alejandro de Humboldt National Park, Cuba
- Alexander von Humboldt National Forest in Peru
- Humboldt Hotel in Cerro El Avila, Venezuela
- Humboldt Street in Brooklyn, New York
The Mare Humboldtianum lunar mare is named after him, as is the asteroid 54 Alexandra.
The Humboldt Tropical Medicine Institute at Cayetano Heredia University, Lima, Peru, was named after Alexander von Humboldt, as well as Humboldt State University in Arcata, California, Alexander Von Humboldt school in Mexico City, Several German schools (including Humboldt University of Berlin) are named after Alexander's brother Wilhelm. In Montreal the German International School was named after Alexander von Humboldt, as well as the Humboldt Schule in San Jose Costa Rica.

## The Alexander von Humboldt Foundation
After his death, his friends and colleagues created the Alexander von Humboldt Foundation (Stiftung in German) to continue von Humboldt's generous support of young scientists. Although the original endowment was lost in the German hyperinflation of the 1920s, and again as a result of World War II, the Foundation has been re-endowed by the German government to award young scientists and distinguished senior scientists from abroad. It plays an important role in attracting foreign researchers to work in Germany and enabling German researchers to work abroad for a period.

## Dedications
Edgar Allan Poe dedicated his last major work, Eureka: A Prose Poem, to von Humboldt. Humboldt's attempt to unify the sciences in his Kosmos was a big inspiration for Poe's project.
Charles Darwin makes frequent reference to Humboldt's work in his Voyage of the Beagle, where Darwin describes his own scientific exploration of the Americas.

## Recognitions by contemporaries
Wilhelm von Humboldt: "Alexander is destined to combine ideas and follow chains of thoughts which would otherwise have remained unknown for ages. His depth, his sharp mind and his incredible speed are a rare combination."
Charles Darwin: "He was the greatest travelling scientist who ever lived."  "I have always admired him; now I worship him."
Johann Wolfgang Goethe: "Humboldt showers us with true treasures."
Friedrich Schiller: "Alexander impresses many, particularly when compared to his brother - because he shows off more!"
Simon Bolivar: "Alexander von Humboldt has done more for America than all its conquerors, he is the true discoverer of America."
Jose de la Luz y Caballero: "Columbus gave Europe a New World; Humboldt made it known in its physical, material, intellectual, and moral aspects."
Napoleon Bonaparte: "You have been studying Botanics? Just like my wife!"
Claude Louis Berthollet: "This man is as knowledgeable as a whole academy."
Thomas Jefferson: "I consider him the most important scientist whom I have met."
Emil Du Bois-Reymond: "Every scientist is a descendant of Humboldt. We are all his family."

# Publications

## Biographies and other works
A good biography of Humboldt is that of Professor Karl Bruhns (3 vols., 8vo, Leipzig, 1872), translated into English by the Misses Lasseil in 1873. A good 1852 biography, 'Lives of the Brothers Humboldt' is freely available (see external links below). Brief accounts of his career are given by A. Dove in Allgemeine Deutsche Biographie, and by S. Gunther in Alexander von Humboldt (Berlin, 1900).
Le voyage aux regions equinoxiales du Nouveau Continent, fait en 1799-1804, par Alexandre de Humboldt et Aime Bonpland (Paris, 1807, etc.), consisted of thirty folio and quarto volumes, and comprised a considerable number of subordinate but important works. Among these may be enumerated
- Vue des Cordilleres et monuments des peuples indigenes de l'Amerique (2 vols. folio, 1810);
- Examen critique de l'histoire de la geographie du Nouveau Continent (1814-1834);
- Atlas geographique et physique du royaume de la Nouvelle Espagne (1811);
- Essai politique sur le royaume de la Nouvelle Espagne (1811);
- Essai sur la geographie des plantes (1805, now very rare);
- Relation historique (1814-1825), an unfinished narrative of his travels, including the Essai politique sur l'ile de Cuba.
The Nova genera et species plantarum (7 vols. folio, 1815-1825), containing descriptions of above 4500 species of plants collected by Humboldt and Bonpland, was mainly compiled by Carl Sigismund Kunth; J. Oltmanns assisted in preparing the Recueil d'observations astronomiques (1808); Cuvier, Latreille, Valenciennes and Gay-Lussac cooperated in the Recueil d'observations de zoologie et d'anatomie comparee (1805-1833).
Humboldt's Ansichten der Natur (Stuttgart and Tubingen, 1808) went through three editions in his lifetime, and was translated into nearly every European language.
The results of his Asiatic journey were published in Fragments de geologie et de climatologie asiatiques (2 vols. 8vo, 1831), and in Asie centrale (3 vols. 8vo, 1843) an enlargement of the earlier work. The memoirs and papers read by him before scientific societies, or contributed by him to scientific periodicals, are too numerous for specification.
Humboldt's effect on American scientists and environmentalists (Clarence King, Jeremiah N. Reynolds, George Wallace Melville, and John Muir) is examined in The Humboldt Current: Nineteenth Century Exploration and the Roots of American Environmentalism, by Aaron Sachs (Viking, 2006).
Daniel Kehlmann's 2005 novel Die Vermessung der Welt, translated into English by Carol Brown Janeway as Measuring the World: a Novel in 2006, explores von Humboldt's life through a lens of historical fiction, contrasting his character and contributions to science to those of Carl Friedrich Gauss.
An essay entitled Journey to the Top of the World details Humboldt's South American exploration and America's interest in him. The essay is chapter one of David McCullough's book, Brave Companions: Portraits in History, (Prentice Hall Press, 1992).

## Humboldt's correspondence
Since his death, considerable portions of his correspondence have been made public. The first of these, in order both of time and of importance, is his Briefe an Varnhagen von Enze (Leipzig, 1860). This was followed, in rapid succession, by Briefwechsel mit einem jungen Freunde (Friedrich Althaus, Berlin, 1861); Briefwechsel mit Heinrich Berghaus (3 vols., Jena, 1863); Correspondence scientifique e litteraire (2 vols., Paris, 1865?1869); "Lettres a Marc-Aug. Pictet", published in Le Globe, tome vii. (Geneva, 1868); Briefe an Bunsen (Leipzig, 1869); Briefe zwischen Humboldt und Gauss (1877); Briefe an seinen Bruder Wilhelm (Stuttgart, 1880); Jugendbriefe an W. G. Wegener (Leipzig, 1896); in addition to some other collections of lesser importance. An octavo edition of Humboldt's principal works was published in Paris by Tb. Morgand (1864-1866). See also, Karl von Baer, Bulletin de l'acad. des sciences de St-Petersbourg, xvii. 529 (1859); R. Murchison, Proceedings, Geog. Society of London, vi. (1859); L. Agassiz, American Jour. of Science, xxviii. 96 (1859); Proc. Roy. Society, X. xxxix.; A. Quetelet, Annuaire de l'acad. des sciences (Brussels, 1860), p. 97; J. Madler, Geschichte der Himmelskunde, ii. 113; J.C.Houzeau, Bibl. astronomique, ii. 168 (A. M. C.).