One of the family possessions was the ancient castle of Tegel, situated a short distance from Berlin, and at this place Alexander spent the greater part of this childhood and youth.

The castle enjoyed the distinction of having more than one interesting legend connected with its history, and the young Alexander and his elder brother William found great delight in weaving strange romances about the place which possessed such a mysterious charm.

The country about Tegel was extremely beautiful, and the castle commanded a view of gardens, lakes, promenades, forests, and towns in the distance, while near by were the picturesque fortress of Spandau, situated on the southern shore of Tegel Lake, and the fine grove reaching on the other side toward Berlin.

Major Humboldt, the father of the two boys, was renowned for his hospitality, and the castles was the scene of almost uninterrupted festivities, the visitors including princes, statesmen, and scholars in the number, and thus the Humboldt children were from their earliest years thrown into the society of some of the most distinguished men of the age.

When he was about ten years of age Alexander saw his father receive Goethe as a guest, the visitor little dreaming that the two fun-loving boys who shyly greeted him would one day become his chosen friends, equally esteemed for their nobility of character and their intellectual gifts; while the children themselves, to whom as yet no dreams of fame had come, thought only of the present moment, and associated their father's guest only with the wonderful stories of which he was the author, and which had so speedily won for him so great a renown.

But such opportunities for seeing the most learned mean of the day could not fail to make an impression upon the minds of the brothers, and they early imbibed the idea that intellectual greatness and individual exertion took the precedence of wealth or rank in the opinion of the truly wise; and thus although a fortunate future might await them inview of their father's position, they early understood that higher distinction could only come from their own earnest effort.

This impression was deepened by the influence of the man whom their father had chosen for their teacher, Heinrich Campe, one of the foremost thinkers of the time.

Campe was a devoted advocate of the new methods of teaching then being introduced into Germany, and found his views warmly supported by Major Humboldt, who desired his children to have the benefit of the advanced school of thought. And it thus happened that the Humboldt brothers had from the beginning the advantage of superior instruction, and had nothing to unlearn when after-years decided their career.

Campe, following the new method, trained his pupils not only in the exercises which develop the memory, but led their minds into new channels, and awakened an interest in the world at large which only increased as the years went on. It was to him that they boys owed their first impressions of foreign countries, and thus from the beginning of their education they were led to take an interest in matters quite outside their own immediate sphere. Campe desired them to become students, not only of the dead languages and mathematics, but of men, manners, and the world in general, and this wish was ardently fulfilled by his pupils.

Although Campe only remained at Tegel two years, his influence was never lost, and extended over the whole lives of his pupils. He was the editor of an edition of "Robinson Crusoe," and made this fascinating volume the groundwork of an interest in foreign countries which only increased with time.

All the old legends which hung around the castle of Tegel failed to excite their imagination to the degree of wonder wrought by the marvelous history of the hero of the desert island; and the familiar fairies, spirits, and genii of their native forests lost their charm in the presence of the actual living Crusoe, whose bravery they might emulate and whose example they both determined to follow.

Thenceforth desert islands possessed a magical fascination, and Alexander avowed his intention of starting for the South Sea at the earliest opportunity. Books of travel were read with an interest never felt before, and the tales of the travelers who now and then visited the castle were listened to with absorbing attention; and the purpose excited by these events was clung to by Alexander with a tenacity that was the more remarkable considering that this delicate health seemed to forbid the possibility of his high hopes ever being realized.

When Campe left eh castle to accept an important position elsewhere, he was succeeded by Christian Kunth, whose influence upon his pupils was as beneficial as that of this predecessor, and who remained their lifelong friend.

The plan of Campe to awaken a love for universal knowledge was also pursued by Kunth, and the Humboldts were thus able to continue their methods of study without any serious interruption. Kunth's interest for the welfare of the boys, and his influence over them, continued even when they came to receive instruction from special teachers; and thus when Alexander began taking lessons in botany at the age of fourteen, of an official who lived near Tegel, it was Kunth who led his mind to contemplate the study only as part of the great system of nature, and kept before him the fact that botany was important not because of itself, but because it led to a better of the universality of the laws of creation.

Thus the necessity of grasping the principle that underlies any collection of facts was early instilled in the mind of the future naturalist, and while learning the Linnæan system of classification he also learned that this knowledge was but a step toward the goal desired by the true seeker after wisdom.

During the years of Kunth's tutorship the Humboldts spent the time partly in Berlin and partly at Tegel, giving the strongest evidence, even in their boyhood, of the diversity of their tastes, William devoting himself principally to the classical studies, while Alexander experience an every-increasing love for natural history.

Great was the delight of the younger brother, therefore, when the choice of a university fell upon Göttingen, for there lived the celebrated Blumenbach, whose knowledge of the natural sciences would be of priceless value to the eager student, and it was at Göttingen also that Alexander formed an intimacy that proved of more than usual importance. This was his friendship with George Forster, a son-in-law of one of the teachers in the university, and a man of fine attainments of unusual originality.

Forster had been one of the companions of Captain Cook in his famous voyage around the world, and this fact at once made him an interesting personage in the eyes of Alexander. Forster was equally attracted toward his ardent young admirer, whose tastes were so congenial, and willingly gave him the benefit of his larger experience. All of Alexander's old enthusiasm for desert islands and foreign travel was aroused by the recital of his friend's wonderful adventures, and as Forster was a great student of natural history his story had the effect of rousing in the mind of his hearer an earnestness of purpose that was invaluable in its influence upon his character.

Hereafter a journey across the sea and into unknown lands was not only looked up on as an opportunity for personal excitement and adventure, but was viewed as a serious undertaking, containing possibilities for grave work in science, and, in fact, with his usual good fortune, Alexander had, on his arrival at Göttingen, fallen in with the very man who of all others could best serve him in his preparation for the serious business of life. From this time there was never any question in his mind as to the nature of this work.

His friendship with Forster but strengthened the already half-formed resolution to become a man of travel and science, and the succeeding years only made this purpose more definite. Works of travel, geography, languages, and natural science were hereafter studied with a view to his future work, and he ardently longed for the time when he might begin his life of travel.

The Humboldts left the university of Göttingen, after a two years' course, and a few months later Alexander, being then in his twenty-third year, started with Forster on his first scientific journey. This was an expedition down the Rhine, through Holland, and over to England, and resulted in the publication of an original theory of the formation of the rocks of the Rhine. This journey was chiefly important because it roused in Humboldt a greater delight in mineralogical studies, and led to a decision to make mining his particular business.

He therefore went to Freiburg the following year to study the metallurgical sciences, and made such rapid progress that in less than two years he was appointed superintendent of the mines in Franconia, with commission to remodel the plan of the working of the mines according to his own ideas.

While in this position Humboldt made many interesting experiments on the chemistry of metals, and also contributed toward the discussion that was then going on between geologists as to the formation of the earth. Although he was so young a man his views were received with attention by the older scientists, and were indeed so accurate as to be incorporated into his later works.

The plan for a great journey to America was all this time maturing in his mind. America was still almost a new world to Europeans as regarded the knowledge of it mineral vegetation, and animal life, and it was Humboldt's desire to be the Columbus who should open this unknown territory to the scientific world. North America, with the exception of a narrow portion lying along the Atlantic coast, was still practically unknown even by the inhabitants of the oldest settlements, and South America was even more a land of myths and ignorant wonder. The mines of Mexico and Peru, the vast profits of which had enriched the Spanish crown in the early days of American exploration, were still regarded as objects of interest whose reality could not be doubted, but the most indefinite and extraordinary accounts were in circulation as to the rest of the continent.

Cuvier, by his scientific analysis of American fossils, had exploded some of the more extravagant theories of the monstrous beasts and birds that were supposed to inhabit the tropical forests, but in other departments the greatest ignorance still prevailed. Marvellous stories were told of the forests, with their strange inhabitants, and of the great rivers, and plains, and the lofty mountain ranges, and volcanoes; but the exaggerated accounts brought by chance travelers to these regions were useless for scientific purposes, and Humboldt resolved to visit those remote countries, view their wonders with his own eyes, and then give to the world a faithful record of his travels, in the hope that such a contribution would be of value to the students of natural history.

Having this idea in his mind he made several short trips to the Alps, Poland, and Italy, which, were designed as a preparation for his great journey, and devoted his entire time to the accurate study of geological formations and similar scientific matters, in order that he might be able to compare his experiences in Europe with his explorations in America. He also devoted much care to the testing of instruments and other practical matters, with a view to making his outfit as complete as possible.

But many things hindered Humboldt in the carrying out of his plans, and years passed and 1799 found him still on European soil, detained by one thing and another, but principally by the war then waging, which resulted in the blockade of many ports, and made it almost impossible for a vessel to sail.

But finally the long-deferred hope was realized, and in June, 1799, he left Spain in a ship which was able to leave port in consequence of a severe storm which caused the blockading vessels to put out to sea, bearing with him the royal permission to explore all the Spanish possessions in America, without condition to hindrance.

They sailed first for the Canary Islands, and a few days after starting Humboldt enjoyed the first surprise of the traveler, in the appearance of immense numbers of jelly-fish which covered the sea in all directions, their colors forming a striking contrast to the waters.

At Santa Cruz they landed and ascended to peak of Teneriffe, and here Humboldt made some observations on its geological formation, which were interesting as foreshadowing the nature of his work in tropical America. It was at this time that Humboldt was first led to observe that mountains and rocks resemble one another, though separated by oceans and seas, while on the contrary, the plants and animals of distant places vary with climate and position.

From the Canaries they proceeded toward the Cape Verd Islands, and thence westward, the usual route of the mariner, and in less than a month from the time of sailing Humboldt saw the Southern Cross blazing in the sky at night, and knew that he had indeed left Europe behind, and was entering those regions of romance and wonder that it had been the dream of his life to see.

The voyage across the Atlantic was uneventful, but not monotonous, as it was Humboldt's first experience as an ocean traveler, and the ever-changing aspect of the sea, the condition of the atmosphere, the direction and force of the winds, together with other phenomena, proved a fruitful source of interest.

In this connection he noticed the difference between the temperature of the air on the land and on the sea, in the same season and latitude, and made some very interesting observations on the blueness of the sky, using an instrument which measured the intensity of the color; his work in this regard possessing a peculiar value, as he was the first traveler who made scientific observations of the sky in the region of equal days and nights.

He also measured the color of the sea, finding that it often changed form blue to green or gray, when there was no apparent change in the atmosphere, and noticing that, contrary to the usually accepted belief, the sea did not reflect the sky, retaining its vivid azure tint often when the sky was entirely covered with white clouds.

Humboldt also made some observations on the attraction of the magnetic needled in those latitude, and thus the voyage of forty-one days was made the beginning of his actual work.

He had intended going directly to the West Indies, but the breaking out of an epidemic on the ship included him and his traveling companion, Bompland, to land on the coast of Venezuela, and led him to decide upon visiting the coasts of South America before proceeding further.

They landed at Cumana, a port guarded by a fortress whose ramparts were formed of a thicket of prickly cactus, which was in turn surrounded by a moat in which living crocodiles served as an effective means of defence. This original fortification was a source of immense interest to Humboldt, as illustrating the ingenuity of the human mind in adapting to its uses the very things which were by their nature inimical to man; and as Cumana had been visited by an earthquake the year before, the traces of which still remained, Humboldt immediately upon landing found himself in a situation well calculated to enliven his scientific interest.

The neighborhood of Cumana was equally full of suggestion, and after making a study of the volcanic soil of the place, and of the history of the earthquakes in order to find, if possible, some law which governed the recurrence of shocks, he started out on his first scientific extrusion in the New World.

This was an expedition to the island of Araya, formerly famous for its pearl fisheries and slave trade, and was not remarkable except as the beginning of a series of small excursions around Cumana, which were fruitful in suggestion, and of much use in preparing the travelers for longer and more important South American journeys. The visit to Araya occurred in August, 1799, and from that time till the following November, Humboldt made Cumana the base of his operations.

During this time he visited many of the old Spanish missions, and was able to study something of the life of the Mission Indians, who lived in little huts surrounded by sugar-cane, maize, and fruit trees.

The impression that the rich tropical vegetation made upon Humboldt was most vivid, and made him realize, as nothing else could have done, that he was indeed in a strange land. He now saw growing in the greatest profusion the trees, shrubs, flowers, and fruits that could only be found in rare botanical collections in Europe, and he and Bompland immediately set about gathering specimens with a zeal what was astonishing to the monks at the Missions, who looked upon their dried plants and scientific instruments with a gentle wonder not entirely unmixed with a little disdain, that human beings should find interest in such unimportant things.

It was during his stay in this region that Humboldt visited some Indians who prophesied earthquake shocks in the near future, a prophecy which was fulfilled after his return to Cumana. For nearly a month before the earthquake occurred Humboldt was able to study the phenomena which proceeded it. At first the sky was covered for a few minutes at night with a reddish mist, then the mist grew denser, the air became hotter and hotter, the sea breezes failed, and the sky grew flame-colored. The inhabitants grew nervous and fearful as these alarming signs succeeded one another, and on the day of the shock the feeling of dread extended even to the animal world. The birds uttered low cried of distress, the dogs howled, and the crocodiles left the beds of the rivers and fled with hideous noises into the forests.

When the shock came the inhabitants rushed into the streets, wild with terror, imploring the saints for aid, and a scene of confusion ensued almost as terrifying to the unfamiliar mind as the earthquake itself. Cumana suffered from several shocks at this time, and Humboldt and Bompland were surrounded by questioners who eagerly asked if their instruments could not foretell the duration of the trouble, or indicate fresh shocks.

The splendid sunset, and the banks of golden clouds tinged with rainbow colors which illuminated the west at the end of this eventful day, were not the least interesting among the strange experiences which Humboldt felt at this time.

In the latter part of November, Humboldt and Bompland left Cumana for Caracas, where they remained two months, charmed with the delightful climate, and interested in making collections of geological and botanical specimens. Caracas was one of the most important towns of South America, and the surrounding country was rich in plantations of citron, figs, coffee, and other tropical productions. The were hospitable, and gave a friendly welcome to the travelers, who were glad to remain a while amid such pleasant scenes before starting out on the great undertaking which had detained them in South America.

This was to explore the Ilanos of the Orinoco and Amazon, and make a scientific survey of those almost unknown regions. After a preliminary excursion to various places of interest, such as the warm springs, the gold veins, the sugar and indigo plantations, which were to be found in the western part of Venezuela, they finally embarked on their journey on the Apure, intending to sail down this stream to its junction with the Orinoco, thence to the Rio Negro, and so on to the Amazon.

The journey was important, for form the moment of starting they traveled through regions hitherto almost unknown to the white man, and abounding in scenes of scientific interest. The river itself was crowded with fish, sea-cows, crocodiles, and turtles, its shores were the home of innumerable flocks of birds, and the woods were filled with monkeys, tapirs, jaguars, and other animals. In the daytime the voyaging was comparatively easy. The Indians who managed the boat were skilled oarsmen, and the constant variety of incident kept up a lively interest; but at night, when the boat was moored, and the travelers had lain down in the hammocks weary with e day's journey, another side of the picture presented itself.

The neighboring forests were filled with the shrieks and howls of the wild animals, many of whom pursued their prey at night, and the knowledge that among these was the jaguar, whose approach always carried dread with it, did not greatly reassure the alarmed travelers, who saw in the waving shadows cast by their camp fires the angry eyes of this terrible foe glaring at them through the darkness, and could discern above the voices of the other animals his hoarse scream, as he pursued hi prey from tree to tree.

The journey on the Apure was largely occupied by Humboldt in the adding to his collections of specimens and making drawings of every object of importance, and was thus very rich in scientific interest.

When they reach the Orinoco, whose broad expanse of waters stretched before them like a sea, they had still greater opportunities for studying ht characteristics of South American scenery, and during their progress a remarkable rise in the river gave a fine chance for making observations on the water-levels.

While on this river they landed on an island owned by one of the Spanish missions, and found that they were considered as suspicious characters by the priests, who could not imagine that they had really left the comforts of home and undertaken the dangers of an unknown country merely for the sake of making botanical collections and measuring the land.

The great waterfalls in the Orinoco were a source of deep interest to Humboldt, who took the opportunity of measure the height of the falls and comparing it with other celebrated cataracts; the noise of the falls was also made a subject of investigation, and as in the solitude of such a region the quiet of the day is never disturbed, Humboldt came to the conclusion that the increased loudness at night was due to the fact that the cold air conducted the sound more perfectly than the warm air of the day.

Humboldt stayed among the waterfalls five days, studying their physical characteristics, and then proceeded on his journey toward the Cassiquiare, which unites the Orinoco with the Rio Negro. He reached the latter stream in due time, but found the passage of it the most difficult in his journey, as the swarms of poisonous insects, a and the impenetrable thickets which lined the shores, made both rowing and landing equally hard. They had to cut a landing place with their axes, while the dampness of the wood, owing to the great amount of sap, made it almost impossible for them to obtain a fire.

But at last the passage was over, and Humboldt felt amply rewarded for all the hardships he had endured when he found that he had actually traced the connection between the Orinoco and the Rio Negro. This event was of the greatest importance to the travelers, as it enabled them to solve the mystery that had hitherto hung over those almost inaccessible regions. The possibility of traveling by water from the Orinoco to the Amazon had been a matter of doubt to Europeans, and the voyage of Humboldt was of the greatest scientific interest, as it settled the question definitely. The drawings which Humboldt made were used to correct the old charts, and the societies of Europe were loud in their praise of the man who had ventured on such a perilous journey for the sake of science.

At this place, also, Humboldt collected some valuable materials for illustrating the peculiar formation of the soil, and was able, from the experience gained, to hint at some general laws of nature in distributing the veins of water over the globe. Having accomplished the great object of his journey, Humboldt now left the region which h had hitherto been regarded as almost mythical by Europeans, and returned to Cumana.

Humboldt now arranged to undertake a expedition to include visits to Cuba, Mexico, the Philippine Islands, India, and Turkey, and as the first stage of the journey, sailed with Bompland for Cuba, reaching Havana a month after leaving Cumana.

They remained in Cuba several months, studying the soil, climate, and vegetation, making many valuable additions to their botanical collections, and observing the condition of the slaves. But the great journey that had been planned was never undertaken, as in Cuba Humboldt heard that a friend with whom he had promised to travel through Chili and Peru, had sailed from France for Buenos Ayres, and he at once determined to return to South America and join him. But on reaching Carthagena, they learned that the season was too far advanced for a voyage on the Pacific, and resolved to occupy their time during the necessary delay by a journey up the Magdalena, hoping to enrich his collections by some rare specimens.

In this he was not disappointed, for they found the botanical treasures of this region equal to those in the Orinoco valley, and in addition to this work, Humboldt was able to make a chart of the river district, another great gift to geographical science.

When this had been accomplished, they left the Magdalena and proceeded overland to Quito, which they reached four months after leaving Carthagena.

The journey was difficult, as the was led through an almost pathless region, but Humboldt improved his time by studying the formation of the rocks and waterfalls, mines, remains of earthquakes, the soil, and the now-covered volcanoes and mountain passes; and although they arrived at Quito in an almost exhausted condition, they considered this part of their experience in South American travel as invaluable. The delightful situation of Quito, with its agreeable climate and beautiful surroundings, soon brought back health and good spirits to the travelers.

The ranges of lofty, snow-capped mountains which bounded the horizon roused anew the love for scientific research, and preparations were made for the ascent of Chimborazo and Cotopaxi.

The volcano of Cotopaxi had always been noted for its terrific eruptions, and the visit of Humboldt to its crater was anticipated with unusual interest by the inhabitants of that region. Humboldt had already found the crater of Pichincha inflamed, and bare of the snow which had filled it so long, a circumstance which excited general alarm in Quito, as indicative of another eruption, and any appearance of danger in the neighborhood of Cotopaxi would have been regarded with even more dread. In 1738 the flames from this volcano had risen above the crater in a ring measuring nearly three thousand feet in circumference; two years later another eruption occurred, the noise of which was heard two hundred miles away; a still later outburst there so many ashes in the air that it was dark for several hours, and the inhabitants of the villages near were obliged to go about with lanterns; but at the time of Humboldt's visit the snow still lay in gleaming masses on the summit, and as it was impossible to reach the brim of the crater he was unable to make the scientific experiments he had anticipated.

He was also unable to reach the extreme point of Chimborazo, as a bottomless chasm stretched directly across his path, but he reached an altitude never before attained by any human being, pushing on his way even after reaching a point where the mercury froze in the thermometer and the blood gushed from the nostrils of the adventurous travelers.

Humboldt now made various tours, fruitful in scientific interest, during which he examined the flora of the district, visited the remains of the great aqueduct of the Incas, and corrected the chart of the Amazon which had been made by a French astronomer, but which Humboldt found to be full of errors. Their travels finally brought them to Lima, where they were able to make some important observations on the climate and in astronomy, remaining there several months for that purpose.

From Lima they sailed for Mexico, and as they passed the snowy peaks of the group an ominous sound reached their ears. It was the roar of Cotopaxi, fifty miles distant, whose snow-capped summit had vanished in a single night, and whose thunderings reached they day and night when they were far away on their journey.

Humboldt carried away from South America a picture so vivid and startling that he said, in after-years, it was only necessary to close his eyes to shut out surrounding objects, to see again the foamy waves of the Orinoco, down which he glided, followed they the shrieks of the jaguars; or the treeless stretches of the llanos, where the moss-covered huts of the inhabitants lie miles apart, and the crocodile and boa, curried deep in the soil, sleep through the long seasons of drought—while the horses and cattle wander about roaring in agony, and the burnt grass falls in dust on the parched ground.

During his journey he had suffered from extremes of heat and cold unknown in the temperate zone; he had lived in solitudes where only plants and animals flourished, and where the foot of main had never trodden before; he had been exposed to ravenous beasts, and had found danger even in the trailing vines and beautiful flowers whose poisonous breath touched him as he passed, but through it all his courage never faltered, and his work for science still went on.

And seldom has it been the fortune of the traveler to open such a world of unexplored beauty to the eye of the untravelled.

South America, with its mighty rivers, lofty mountain-ranges, picturesque inland lakes, its llanos, varying from scenes of desolation to the luxuriant beauty of tropical vegetation; with its fabulous mineral wealth, its forests of mahogany and rosewood, its vast herds of horses and cattle roaming in undisturbed freedom over the immense plains; its flourishing cities, in strange contrast to the secluded missions that were scattered in places remote from the world, its ruins of old Peruvian towns, and remains of a dead civilizations, were all calculated to inspire the mind of a traveler like Humboldt—and when to this was added the knowledge that all this beauty of city and plain lay at the mercy of the dreaded earthquake and volcano, which were liable at any time to destroy it forever, the interest could not fail to be increased.

In Mexico Humboldt's most important scientific work consisted in certain astronomical observations by which he arrived at the correct longitude of the city of Mexico, which had until then been wrongly given on the maps. He also visited the celebrated mines of that country, devoting much time to the study of the ores, and made important observations on the formations of the volcanoes of the region; the antiquities of Mexico were also a source of great interest to the travelers, and much time was spent in examining them and transcribing the descriptions to their journals.

At last the great American journey came to an end, and, after a short trip to the United States by the way of Havana, Humboldt sailed for France and reached Bordeaux in August, 1804, five years after his departure from European shores.

The knowledge that Humboldt, who had more than once been reported dead, had actually returned to his native land, bringing with him his valuable collections, created an immense excitement all over Europe, and his name soon became a household word.

For the first time Europeans had an accurate and life-like picture presented to them of the New World, which had always possessed such a mysterious charm, and as they read the fascinating descriptions of Humboldt, they followed him in imagination through all his wonderful journey. With him they sailed up the Orinoco, traversed the llanos, crossed the snow-fields of the Andes, and visited the tropical forests; and the popular fancy, not content with actualities, threw over the adventures of Humboldt even a more magic spell. It was said that in his western tour he had fought and conquered giants, visited the tombs of dead nations and learned their buried secrets, had his courage tested by encounters with races that were but half-human, and had learned of Nature in her great solitudes the secret which governed the life of man, and the wisdom of all the ages. And though this view of Humboldt was but the result of that love for the marvelous which is ever seeking something new, it did not lessen the fascination which was attached to his mane, and he was regarded as a second Marco Polo, whose adventures were more romantic and exciting than any tale of the "Arabian Nights."

For many years after his return Humboldt spent his time in preparing the complete history of this travels in America, giving public lectures, and perfecting his great theory as to the nature and development of the plan of the universe.

But during this period of twenty-five years he had ever before his mind a great journey to Central Asia. With this in view he studied the languages, geography, and history of the East, as well as the existing descriptions of the physical formation of the country, and in 1829, having completed all his arrangements fro an extensive tour, set out for India. Humboldt was accompanied by a number of scientists, and the expenses of the journey were to be defrayed by the Russian Government, which was desirous of obtaining accurate scientific reports of the mineral wealth of its dominions.

The expedition left St. Petersburg in May, 1829, and was absent eight months, during which time Humboldt's industry was indefatigable. During this time he explored the Ural formations, and gained an important insight into the gold and platinum deposits, besides discovering several new minerals; visited the Altai Mountains, and made an important expedition to the Caspian Sea for the purpose of analyzing its waters and obtaining specimens of fish, besides making many observation on the climate, soil, and geological formation of the mountains.

The journey was a most important one for science. Previous to this there existed only the vaguest ideas of the geography of Central Asia, the connection of the mountain-chains, and the productions of the soil; but Humboldt's accurate survey of the hitherto unknown territory put geographical knowledge on a firmer foundation, and gave to the world a clear idea of that interesting land which possessed a charm for all nations as being the supposed first home of the human race. Humboldt proved that Central Asia was neither a broad plateau nor an immense cluster of mountains, as had been supposed, but that it was crossed by the four mountain-systems which have exercised an immense influence on the migration of nations, and helped for form the history of the world.

Humboldt also made important observations on the boundary of eternal snow, and, in his study of the winds and tides and their relation to climate, and to the forms of the continents, deduced a theory of the different temperatures of places in the same latitude but at great distances from one another.

The entire result of Humboldt's travels and studies was incorporated in his great work called "Cosmos," which was complied from his notes, and in the composition of which he was aided buy Cuvier and other naturalists. "Cosmos" contains a theory of the formation of the universe, and embraces observations on the heavens, mountains, earthquakes, the sea, the earth's crust, the atmosphere, the geography of plants and animals, the races of men, the form, density, latent heat, and magnetic power of the earth, and the aurora borealis.

It is the most exhaustive work ever by a single mind, and shows, as nothing else could have done, the extent and originality of Humboldt's powers. Besides the valuable contributions to geographical and geological knowledge, Humboldt's theories of the distribution of heat and magnetism were of special importance. His observations on the magnetic needle and the aurora borealis were of the greatest service to science, and it is largely due to him that observatories have been erected all over the world, from Canada to the Cape of Good Hope, and from Paris to Pekin, with special reference to the study of the earth's magnetism.

Humboldt also devoted much time to the study of the isothermal lines, or lines of equal temperature which connect different places, and likewise the sciences of climatology and geognosy may be said to date from his time.