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 Aimé Bonpland (with whom he conducted much of his scientific exploration).
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 Göttingen, 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 über einige Basalte am Rhein (Brunswick, 1790).
Humboldt's passion for travel was confirmed by friendships formed at Göttingen 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 Universität 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. Köhler. 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 über die gereizte Muskel- und Nervenfaser (Berlin, 1797), enriched in the French translation with notes by Blumenbach.
Armed with powerful recommendations, they sailed in the Pizarro from A Coruña, on June 5, 1799, stopped six days on the island of Tenerife to climb Mount Teide, and landed at Cumaná, Venezuela, on July 16. 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 Cumaná, Humboldt observed, on the night of November 11–12, a remarkable meteor shower (the Leonids). 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 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 , 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.
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 December 7, 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 encyclopædic 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 Parreño, 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 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 May 12, 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 September 18, 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 Encyclopædia 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.
His brother, Wilhelm von Humboldt, died in Alexander's arms on April 8, 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.
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 encyclopædia 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.
Much of Humboldt's private life remains a mystery because he destroyed his private letters.
In 1908 the sexual researcher Paul Näcke, 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 José 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.
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:
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 Montréal the German International School was named after Alexander von Humboldt, as well as the Humboldt Schule in San Jose Costa Rica.
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!"
Simón Bolívar: "Alexander von Humboldt has done more for America than all its conquerors, he is the true discoverer of America."
José de la Luz y Caballero: "Columbus gave Europe a New World; Humboldt made it known in its physical, material, intellectual, and moral aspects."
Napoléon 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."
Robert G. Ingersoll: "He was to science what Shakespeare was to the drama."
Le voyage aux régions equinoxiales du Nouveau Continent, fait en 1799-1804, par Alexandre de Humboldt et Aimé 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
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 comparée (1805-1833).
Humboldt's Ansichten der Natur (Stuttgart and Tübingen, 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 géologie 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).