Popular Science Monthly/Volume 80/April 1912/Alexander von Humboldt
|ALEXANDER VON HUMBOLDT|
By Dr. EDWARD F. WILLIAMS
WITH Baron von Humboldt, says the late Professor Louis Agassiz, "ends a great period in the history of science: a period to which Cuvier, Laplace, Arago, Gay-Lussac, De Candolle and Robert Brown belonged." It was a period of tireless research, of important discoveries, of brilliant generalizations. It was a period in which the specialist appeared, and secured for himself an honorable position. Yet there were men, and among them Humboldt the most distinguished of them all, who were deeply interested in all departments of science, men who sought to master at least their elementary principles and to render themselves able to judge intelligently concerning the conclusions which were reached. Since Humboldt passed away it is doubtful if any one has lived who in the extent and accuracy of his knowledge, the breadth of his vision and the soundness of his judgment can be compared with him as an equal. All the more true is it that his death in 1859 closed an era in the scientific world.
It was in this year that Charles Darwin published "The Origin of Species" and that the Fraunhofer lines of the spectrum were discovered. The theory of evolution was the outcome of studies which Darwin's book compelled the scientific world to undertake. With the full, or even partial, acceptance of that theory new methods of study have been introduced into nearly every department of learning. In the face of such a theory it has been impossible to be satisfied with the old views of history, literature, philosophy, theology, to say nothing of science. It is therefore a matter of no little interest to know what were the views of Humboldt and his co-laborers during the period above mentioned, upon which the foundation of a new era was built. For a clear and accurate statement of the scientific knowledge of his time no work is more worthy of confidence than Humboldt's "Cosmos", of which Vol. I. was published in 1845, Vol. II. in 1847, Vol. III. in 1850, Vol. IV. in 1858 and Vol. V. soon after the author's death. The earlier editions were constantly improved, and the entire edition, furnished with notes, containing extracts from private letters or publications of distinguished men which are of great interest and value, has appeared again and again. Admitting, as we must admit, that many, perhaps most of the conclusions reached in this work, have been set aside by later discoveries, the material gathered and arranged in Volumes I. and II. will always be worthy of consideration and the methods employed in securing it will never fail to be suggestive and useful. That his opinions would require modification, and that some of them might be rejected altogether, is what Humboldt himself anticipated. He calls attention repeatedly to the fact that he and his fellow students were on the threshold of discoveries which might change the entire scientific outlook and furnish even the next generation with an immense advantage over his own.
Friedrich Heinrich Alexander von Humboldt was born at Tegel, near Berlin, on September 14, 1769. He died in Potsdam, where his house is still shown to visitors from every civilized country, on May 6, 1859. His elder brother, William, was distinguished as a statesman, diplomatist and linguist. As the founder, while minister of public instruction of the University of Berlin, he made a great contribution to the intellectual development of the German people. The father was a major in the Prussian army and had been chamberlain at the court of the king. The mother, Marie Elizabeth von Colamb, the widow of Baron von Hollande, was a woman of rare gifts. She devoted herself almost entirely to the training of her two sons, her only children, William and Alexander. As the father died when Alexander was but ten years old, the responsibility of their education fell upon her. Fortunately the family was wealthy, so that private teachers could be provided for the boys at Tegel, among them men like J. H. Camp, famous for his ability to impart knowledge; Christian Kunth, eminent in the educational world, and T. T. Engel. From Tegel the boys were sent to Berlin and put under the care of specialists, whence they were removed to the University of Frankfort on the Oder, thence to Göttingen, where Alexander studied philology and archeology under Heyne, and gave special attention to the philosophy of Kant. His natural love for science was deepened and strengthened by his association with Professor Blumenbach, one of the great men of the university. Destined for business, young Humboldt went from Göttingen to Hamburg and entered the commercial school of Bursch, where he studied modern languages with much zest and listened to lectures on banking and trade. But he soon found that his love for science was greater than his love for money-making, and for this reason, without wholly giving up the thought of a business career, he left Hamburg for the mining school at Freiburg, where he enjoyed the instruction of Werner, the geologist, of the equally famous Leopold de Buch and of Andre del Eio. In a single year he made such progress that in 1792 he was appointed director general of the mines in the district of Franconia and Aspach, with headquarters at Bayreuth. In this position he remained five years, but while faithfully discharging the duties of his official life he found time for brief visits to the Tyrol, Switzerland and Lombardy for the study of botany and geology. With George Foster, a friend of his student years. and the person to whom, as he often declares, he owed his first impulse to the life he led later, he had previously visited England, Holland and Belgium. It was this George Foster, the companion of Captain Cook on his second voyage round the world, who suggested to Humboldt his travels and researches in the tropical world.
As an author young Humboldt had already given proof of far more than ordinary ability. At Göttingen he had written a book on the "Basalts of the Rhine," and in 1792 published a striking essay on the "Fossil Flora of Freiburg." While inspector of mines, employing the discoveries of Galvani, he published two volumes, still frequently consulted, bearing the title, "Über die gereiste Muskel- und Nervenfassen nebst Vermuthengen über den ehemischen Process des Lebens in der Thier- und Pflanzenwelt," Berlin, 1797.
The death of his mother, to whom he was warmly attached, and the increase of his income made it possible for him to carry out longcherished plans for travel and the study of nature in the tropics. Eesigning his position as inspector of mines, he visited Vienna and Paris for special studies and for the purchase of instruments and instruction in their use. In Paris he met Gay-Lussac, Laplace, Arago, Berthollet, and Aimé Bonpland, a young botanist who became his companion in travel and research, and in whom he found the friend and assistant whom he needed. Failing in their attempts to make satisfactory arrangements for explorations in Egypt and Central Africa, the two men finally accepted the protection and assistance of Spain, and decided to devote themselves to the study of the physiognomy, the plant and animal life of the tropical regions of South and Central America and Mexico. At the head of an expedition which in equipment and retinue had hardly been equalled since the days of Alexander the Great the two men sailed from La Coruña in northwestern Spain, June 5, 1799, and landed at Bordeaux, France, on their return home, June 3, 1804. During their absence they had explored Venezuela, ascended the Orinoco 1,800 miles and learned that its head waters are connected with those of the Amazon, had sailed up the Magdalena, settled for a time at Quito and made themselves thoroughly acquainted with the west coast of South America almost to the southern limits of Peru. They had ascended Chimborazo to the height of 19,000 feet, had studied carefully the crater of Cotopaxi and learned all that could be learned at the time concerning the physiognomy of the country. They had studied the forms of life, animal and floral, observed the variations of temperature at different levels above the sea, the arrangements of the mountain chains, the situation and character of volcanoes, active and extinct. They had studied under favorable conditions the celestial phenomena peculiar to the tropical regions and given special attention to the zodiacal light. From the people and their own observation, they had learned all they could learn concerning the country, its civilization and history, its institutions of culture and religion, its resources, agricultural and pastoral, its mines, its timber and its capacity under more favorable conditions to contribute to the sum of human happiness. They had made use of the discoveries of previous visitors, like Condamine and Bourguer of the Academy of Sciences in Paris, who were in the country from 1742 to 1747, and by their observations had made it easier for future explorers, like Boussingault, who followed them twenty-three years later, to profit by their stay in the country. Incidentally Humboldt learned the value of quinine as a medicine, and is to be credited, in part at least, with having made it known in Europe. He and his companions ascertained the location of places by astronomical methods, noted accurately the movements of the barometer so important in determining the character of the climate, and did not overlook at all the botany, the mineralogy, the geology, or even the archeology of the country. Having completed their observations in South America and made a vast collection of specimens of various sorts, which they sent to Paris, they sailed in 1803 for Acapulco, Mexico, where in studies of that country and of Central America they spent nearly a year. Only a few weeks were given to the United States, whence they sailed directly to Bordeaux, France.
Having reported to the King of Prussia and passed nearly two years in and around Berlin, Humboldt obtained leave to visit Paris and arrange for the publication of the results of his explorations. The work which he had thought would occupy him possibly three or four years extended to twenty and even then was unfinished. In Paris, of which he was extremely fond, he associated himself with some of the ablest living scientists of France and with their assistance gave to the world, during the years 1807-1827, thirty volumes of description and discovery. If the scientific world was astonished at the contents of these volumes and the regularity with which they appeared, it soon found that the knowledge for which Humboldt made himself responsible was as accurate as it was extensive. Many of these volumes, in which more than two thousand very costly illustrations appeared, were written by Humboldt's associates, but no one of them left the press without his oversight and approval. It is little wonder that his name was in high repute in every part of the civilized world, that he was chosen a member of nearly every learned society in Europe, or that by general consent he was accounted the first scientific man of the age. This reputation, so early acquired, he retained till his death. Nor were his honors derived from the scientific world alone. While living in Paris he was often employed by his king as a diplomat, and with great profit, for he was a favorite at the court and in the best social circles of the city. A little above medium height, with regular features, beaming eyes, a rare charm of manner, and with a capacity for friendship rarely equalled (it is said he never lost a friend) he was almost as famous for his social as for his scientific victories. Yet he never married.
It was with real sorrow that he obeyed the command of his king and left his dearly loved Paris to pass the remainder of his life in Potsdam. He was in the fifty-ninth year of his age, in perfect health and deeply interested in every department of learning as well as in those special fields to which he had given personal attention. A home was provided for him at Potsdam, a liberal salary paid him regularly, so that, barring the demands which the king made upon him for diplomatic services (and these were not infrequent), as a companion of his official visits, or as a visitor at the palace, he was free to pursue his studies. The German public, proud of his renown, rejoiced in his return to his native land and read with increasing interest and enthusiasm whatever came from his pen.
His lectures at Berlin in the winter of 1827 and 1828, which formed the basis of "Cosmos," were heard with astonishment and delight.
A man like Humboldt, so widely known and so thoroughly trained as an explorer and observer, could not long be permitted to remain quiet in any one place. At the request of the Czar of Russia, under his protection and at his expense, with Ehrenberg, the microscopist, Gustav Rose, the chemist, and Menscherlisch, an engineer, he made a rapid but intelligent survey of Asiatic Russia, giving particular attention to the Ural and Aral Mountain chains. It was on this journey that diamonds were discovered in the Ural Mountains and secured to the government for its control and profit. Ehrenberg and Rose published separate accounts of this journey and Humboldt's "Central Asia" is an enlargement and revision of his first report, which appeared simply as a fragment, on the geology and mineralogy of the country.
While in Paris he had experimented with Gay-Lussac on the nature and qualities-of gas, and with him as a companion had visited Rome, where his brother William was the Prussian minister, in order to study magnetism. It would take a good-sized volume to give an account of the various services he rendered the king, and of the journeys he made as a diplomat, nearly always with success, and in the interest of science. He was in the seventy-sixth year of his age when he made public his intention of writing that great work of his life known as "Cosmos." Previous treatises he looked upon as preliminary sketches compared with the work he would now compose and in which he would try to give an accurate and sufficiently full account of all existing scientific knowledge. In this work, while presenting general rather than detailed conclusions or statements, he would show that nature, in spite of her seeming complexity, is yet a unit and governed by a definite and well-ordered plan. A master of the materials furnished by the most eminent scientists of the day, without claiming for himself to be an authority in any single department of science, he believed himself better fitted by reason of his acquirements, his acquaintance with the scientific men of every country, his wealth, his relation to the king, his leisure, than any other living man to write the book he proposed. He had the promise of assistance from the representatives of all the sciences, and through private correspondence and their publications could obtain from them the latest and most accurate information on the topics he wished to discuss. It is not strange that one of the striking features of "Cosmos" should be its notes, which contain extracts in many cases from private letters and from publications in journals rarely seen, by men whose names Humboldt seems to take pleasure in mentioning, and to whom he never fails to give full credit.
Yet, modest as he is in reference to his own acquirements, he may justly be regarded the founder of the sciences of meteorology, terrestrial magnetism and the physics of the sea. To him more than to any man of his time is due the interest in the study of the currents of the air. It was at his suggestion and after his plans that the Russian government established, from one end of its dominions to the other, stations for the observation and record of magnetic phenomena. It was through his influence that England did the same in her territories, and that other countries have to a certain extent followed these examples. Perhaps it may be added that he is the founder of the science of geodesy. At any rate he was the first to give a full and complete picture of the physical features of the earth and to call attention to the effect of these features and of the temperature of a country upon its inhabitants. The tracing of isothermal lines is due to him. In fact, during his life few new steps were taken or changes made in scientific study without suggestions from him or consultations with him. One of his characteristics was his fondness for young men, and the pleasure he took in aiding them. If he was a little vain, apparently somewhat self conscious, it was by no means unnatural. The friend of kings, a social lion, a successful diplomat, a classical scholar of nearly the first rank, well versed in history, ancient, medieval and modern, at home in modern languages, a master of the best literature of the century, through his brother William, well acquainted with oriental literature and with the conclusions of the comparative study of language, the pride of the German people, recognized on all sides as worthy of the highest honor a man can receive from any source whatever, it would be contrary to nature not to be influenced to some extent by the flattery which came from every side. Without an exception the scholars of Europe recognized his greatness and his eminent fitness for the work he proposed to undertake. The work had been on his mind for at least twenty years. For it he had gathered material, had pursued special studies, made special visits, cultivated the friendship of eminent men, by constant thought formed the plan which he finally carried out, of presenting in clear readable form an account of all that had been discovered and accepted as worthy of belief in the scientific world. As we think of this aged but vigorous man sitting down in his study in Potsdam with the learning of the world at his command, with every literary or scientific man in Germany or France or Italy or Russia ready to furnish any information he might ask, we can not help sympathizing with him in his conviction that he was indeed the best man living to write a book like "Cosmos." The reports published in Paris had, in his eyes, only prepared the way for the generalizations he would now make. Yet to the ordinary man they seemed complete in themselves. They covered a vast field of exploration and study. They had engaged the labors of some of the most eminent men in their departments for twenty years. These reports, arranged in six sections filled thirty volumes. These sections are as follows, viz.,
I. Historical, Geographical and Physical Atlas; Views of the Cordilleras and of the Native Peoples of America.
II. Observations on Comparative Anatomy and Zoology.
III. Political Essay on the Kingdom of New Spain.
IV. Astronomical Observations; Trigometrical and Barometrical Measurements.
V. Essay on Geological Basiography.
VI. Equatorial Plants.
In the International Encyclopedia it is asserted that Vols. I.-XIV. were written by C. S. Kunth, the botanist. They treat of botany almost exclusively. On the South American journey hundreds of new species of plants were discovered and described, and specimens of them sent to Paris. The general title of this extensive work was "Voyage aux regions equinoxiales du Noveau Continent fait en 1799. . . 1804 par Alexandre de Humboldt et Aimé Bonpland." Volumes XV. and XVI. are an "atlas pittoresque."
With the exception of Volume XX. which is devoted to plants. Volumes XVII.-XXII. are occupied with physical geography, geognosy and astronomy. Volumes XXIII. and XXIV. are given to zoology, and Volumes XXV. and XXVI. to a description of the countries of Spanish America. Volumes XXVII. to XXX. contain Humboldt's own narrative and notes upon the countries visited. Unfortunately this narrative was never quite finished. The original work contained the "Essai politique sur royaume de la Noveau Espagñol," the "Essai politique sur l'isle de Cuba," and "Vues des Cordilleries." Special sections of this immense work appeared from time to time under individual titles, and as composed by specialists of distinction. Humboldt's "Ansichten der Natur "was very popular in Germany, as was an edition of his works published in 1864-1866. In Bruhn's "Life of Humboldt," it is shown that he made special contributions to petrography, vulcanology and seismology, that he pointed out the effect upon civilization of the cultivation of the soil in different climates, and drew attention to the languages, architecture and customs of the ancient peoples of South and Central America and Mexico. He was the first, so it is claimed, to mark the decrease in intensity of magnetic force from the poles to the equator. At any rate, his journey to the tropical possessions of Spain in the new world gave a very decided impulse to the study of natural history.
It is not strange that a man with his extensive knowledge, his varied experience as a traveler and the resources of the scientific and literary world at his disposal should desire to write and publish a work that should set forth in clear and accurate form all that in his time was known of the earth and the celestial bodies. If any man was ever justified in the belief that he could satisfy his ambition in this respect it was Alexander von Humboldt at the age of seventy-six.
"Cosmos" is a history in outline of the physical contemplation of the universe. Its aim is to show the unity of the universe. It is not a history of the natural sciences as such, rather an attempt to point out the close connection of all the forces of nature. To do this all possible sources of information are laid under tribute. In his study of what has been done and is now known, Humboldt pledges himself to follow three laws, or to be guided in his thought and writing, by three principles: viz.,
1. To show the efforts of reason, through meditation upon phenomena to obtain a correct knowledge of natural laws.
2. To consider events which have suddenly enlarged the horizon of observation.
3. To show what has been the result in the enlargement of the fields of human knowledge through the discovery of new means of sensuous perception, or of new organs, or instruments by means of which we are brought into closer touch with terrestrial and celestial objects. Thus in the telescope and the microscope we have new organs of perception.
Starting from the basin of the Mediterranean, with its three contiguous closed seas and its three peninsulas, Spain, Italy and Greece, the discoveries made by voyages to other countries are named, and the fact stated that the earliest civilizations were developed in countries rich in rivers, as Egypt, Messopotamia, India and China. The author takes pains to emphasize the exceptional men who lead in new movements in travel, who make startling and important discoveries. Nor does he overlook the events which mark the beginning of new eras in the world's history. He has the rare faculty of making us see how striking contemporaneous events often are. For example, when Columbus discovered America, Copernicus was studying astronomy with Brudzewski in the University of Cracow. The rapid extension of knowledge at the beginning of the seventeenth century was due to the studies and discoveries of Galileo and Kepler, at its close to those of Newton and Leibnitz. It was in this century that the problems of light, heat, magnetism, double refraction and the polarization of light were partially solved. Some traces of a knowledge of the results of the interference of light are seen in the works of Grimaldi, Hooke, William Gilbert and Halley. But it was the discovery of the calculus by Newton and Leibnitz, and its use by scientific men, that the new impulse was given to the study of astronomy and physics. Some of the marked periods in history may be mentioned. One of these periods was that of the Argonautic Expedition under Jason in search of the Golden Fleece which took place about 1200 B.C. Another was the passage of Europeans into the regions of the Euxine and the settlements made there by the Greeks; another the expeditions of Alexander the Great, whose campaigns have been called scientific as well as military. Another period of great importance is marked by the growth of scientific interest, especially in Egypt, under the Ptolemies, and still another by the dominion of Rome and the influence of the Cæsars. In the Middle Ages, Arabs who had absorbed and added to the learning of the Greeks, brought it back from Bactria, a kingdom which lasted 116 years, to western Europe and thus in the fifteenth century became the pioneers in the new world of awakened thought. Phoenicians led in the early voyages of explorations. The Greeks followed and established colonies on the coasts of Asia Minor and on the southern shores of the Black Sea. Wherever Romans went they remained as conquerors. From the Phœnicians we have few descriptions of nature. From Roman writers like Cicero, Ovid, Livy, Cæsar, there are more. There are some also in the writings of the Greeks from Homer and Hesiod down, but for the most part the interest centers in man, not in the beauty or striking features of the region in which he lives. The Hebrews are not insensible to the importance of natural scenery upon the character of men, nor are they unable to give vivid utterance to the impression which sublime scenery, as witness Ps. 104, makes upon them. From the christian fathers, as in the writings of Basil the Great, whom Humboldt especially admired, we have many descriptions, though even here the human element is always of prime importance. The Aryan races, natives of India and Persia, recognize the charms of nature, but still men are the objects upon which interest in their writing rests. In the early Italian writers, and in the poets to the time of Petrarch and Dante, there is evidence of a growing fondness for scenes of natural beauty. Calderon is a representative of many a Spanish poet who does not think it beneath his dignity to convey to others some of the impressions which the vision of a lovely landscape has made upon the mind. Camoens in his Lusiad proves that this is true for Portugal also. In the fourteenth and fifteenth centuries travelers were careful to describe the strangeness and at the same time the attractions of the regions they visited. Thus the way was prepared for Columbus, who had the ability to give a description in a single luminous sentence which lingers in the memory, and creates a desire to see for oneself the places of which he writes. Humboldt thinks that landscape painting was not without an influence on early attempts to write out descriptions of nature. Landscape gardening made its contributions also, through the rare plants and trees, flowers and fruits, it presented to the eye. But the work of others is only an incentive to Humboldt to see with his own eyes and to set forth in picturesque language the features and striking characteristics of the countries in which he has lived. In doing this he is careful to show the effect of climate and the physical features of a country upon the well-being of men, for even he can not forget that it is for man that this world exists, and that it is to be studied for his sake and not for itself alone.
Astronomy, as known prior to the second half of the nineteenth century, receives extensive treatment in the "Cosmos." With its history and with the character and acquirements of the men who from the days of Aristarchus of Samos had been scanning the heavens and penetrating into the secrets of the starry worlds, Humboldt had made himself thoroughly familiar. What would he have said had he been as familiar with the principles of astrophysics? More ready than ever, assuredly he would have been, to assert his belief that we are standing on the threshold of a new era in scientific knowledge, and of discoveries which can not fail greatly to extend the horizon of our vision.
If he is careful to give credit to the early scientists with their limited acquirements, he is none the less so in his reference to the men of his day. Of Ehrenburg, his companion on his Asiatic journey, and a friend from whom he often received aid, he speaks as "the greatest microscopist of the age," "the highest authority in the study of microscopic organisms." Ehrenburg was one of the young men in whom Humboldt took deep interest. He was born at Delitsch in 1795 and died in Berlin, 1876. From 1820 to 1825 he was engaged in explorations in Egypt, Abyssinia and Palestine, and from 1838 to 1854 gave his attention almost exclusively to the study of microscopic organisms. For a translation from a Japanese Encyclopedia of an article on volcanoes Humboldt gives grateful recognition to Stanislaus Julien and prints it in full in Vol. V. of the "Cosmos." He refers to his brother William, whose death he mourned as long as he lived, as half his life, as an authority, as his treatise on the Kawi language shows, in the science of the comparative study of languages. Professor Waagen, of whose information he often makes use, the director of the gallery of painting in Berlin, is declared to be "a profound and cautious connoiseur of art." Generous praise is given Ottfried Müller, author of the "Archeologie der Kunst." Of Goethe and Schiller he speaks in terms which not only indicate his high esteem for their abilities, but the intimacy of his relations with them. Ludwig Tieck is an honored correspondent who has answered his questions concerning Calderon's and Shakespeare's descriptions of nature. Of August de Chateaubriand, who died July 4, 1848, he speaks as his "old friend, famous for his descriptive powers." Nor does he fail to speak of Arago in the most affectionate terms, quotations from whose letters fill many pages of notes, and for whose attainments he had profound respect.
Humboldt begins his work with a description of celestial phenomena and then comes down to the earth. He refers with respect to the labors of Hipparchus, Eratosthenes and Euclid, as of mathematicians of the first rank. He credits Aristarchus of Samos with having anticipated Copernicus in his theory of the universe. He recognizes the value of Strabo's geography, written after its author had entered his eighty-third year, and makes use of the works of the Plinys, the elder and the younger. To Hipparchus of Sicily, and Galen of Pergamos, physician and anatomist, he refers as men of the highest attainments. He praises the Arabs not only for their observations of the heavens and their careful mathematical calculations, but for their skill in chemistry and their experiments in order to discover its value in medicine. He says they were acquainted with many of the qualities and uses of sulphuric and nitric acid, and were aware of the fact that bodies can be decomposed and reunited. He is at pains to show how nearly related to each other most discoveries are, and that they are made in almost every instance by men who miss only by a little the discovery of some great truth which a little while after, other more fortunate men see. Preparations, Humboldt tells us, for the voyages of great sailors just before Columbus were made in the twelfth century. Three men in the thirteenth century, Roger Bacon, Albertus Magnus and Vincentius of Beauvais, would have been eminent in any century. As independent thinkers. Duns Scotus, William of Occam and Nicolas of Cusa led the thought of the world from the time of Ramus, Campanella and Bruno to Descartes. It was in 1250 that Vincentius wrote his "Secula Naturæ" for the use of St. Louis and his queen Margaret. This and other works of his were forerunners of of the "Margarita Philosophia" of Father Reisch, published in 1486, a book which Humboldt praises and of which he made some use and which he declares was instrumental in diffusing knowledge in the last half of the fifteenth century. Of the writings of Father Joseph Acosta, the Jesuit who published his "Natural History of the Indies" in 1590, it is enough to say that they prepared the way for works of Vossius, which Newton used, and in which Humboldt finds the groundwork of physical geography. Many events which were of importance in his day Humboldt traces back to the fifteenth and the beginning of the sixteenth centuries. These are the doubling of the Cape of Good Hope by Vasco di Gama, the discovery of America by Columbus, the voyages of Amerigo Vespucci and his son, and Magellan's circumnavigation of the globe. That same period witnessed a rare manifestation of intellectual power as well as the growth of a desire for religious freedom. It was in this period that the Laocoon, the Torso of Hercules, the Apollo Belvidere, the Medicean Venus were rediscovered. Michael Angelo was living in Rome, Leonardo da Vinci in Venice. It was the period of Titian and Eaphael, of Holbein and Albert Dürer. Fourteen years after the discovery of the new world, or in the year that its discoverer died (1507), Copernicus made known his system of the world. Almost immediately followed an era of invention and the skilful use of instruments of research. New wonders in the heavens were constantly appearing. The results of mathematical calculations made astronomy an exact science. The law of gravitation, Kepler's laws of motion, knowledge of the pressure of the atmosphere, of the propagation of light, its laws of refraction and polarization, the radiation of heat, electro-magnetism, reentering currents, vibration chords, capillary attraction, in their discovery and in the increase of knowledge concerning their nature and importance, are all closely connected. Galileo, Lord Bacon, Tycho Brahe, Descartes, Huyghens, Fermat, are more nearly related to each other in the work they each accomplish than is generally understood. A list of some of the subjects treated in Volume I. of "Cosmos" will give a hint of the wealth of learning it contains and of the ability of the author to bring together a vast amount of knowledge on a great variety of topics without confusing his readers or for a moment permitting them to lose sight of his purpose to show how all knowledge is related and that the heavens and the earth belong to the same general plan, and are under the government of a single intelligent will. Beginning with a review of what is known of celestial phenomena, he comes down to those which are terrestrial in their character. Under celestial phenomena sidereal systems are treated as well as the solar system. Comets are carefully considered, aerolites, also, the zodiacal light and the milky way with its starless openings. Under terrestrial phenomena are grouped such subjects as the distribution of mountain chains, great plains, arid and fertile, oceans, inland seas, lakes, rivers, the figure of the earth, its internal heat, terrestrial magnetism, the aurora borealis, geognostic phenomena, earthquakes, gaseous emanations, hot springs, salses, volcanoes, isolated, in groups, and along certain lines, paleontology, geognostic periods in the earth's history with reference to certain marked changes in the physical features of the globe, atmospheric pressure, meteorology, the snow line of mountains, hygrometry, atmospheric electricity, organic life, the geographical distribution of plants and animals, of races of men and of language. One can see from this enumeration of titles how broad is the outlook over the world of knowledge in this little volume of less than 400 duodecimo pages. On every subject treated Humboldt either gives his own opinions or those of men whom he deems competent to speak. On astronomy we have not only what the ancients have thought, and the astrologists, but what the Herschells, Maedler, Arago, Leverrier, Laplace, Bessel of Königsberg, an authority on comets, and Faye, discovered and taught. Aerolites, shooting stars, fire balls, meteoric stones, are given extensive treatment. Aerolites are said to be "small bodies revolving with planetary velocity, and in obedience to the law of general gravity, in conic sections round the sun." Showers of shooting stars were observed by Humboldt and his companions in Cumana, S. A., in 1799 and in 1832-33 by Professor Denison Olmstead, of New Haven, Ct. To the consideration of this phenomena men like Brandes, Benzenberg, Bessel, Arago, Eduard Biot, Poisson, the mathematician, and Berzelius, the chemist, gave much time and thought.
The first person to observe and report upon the zodiacal light, according to Humboldt, was Dominique Cassini, of Bologna. He published his views in 1668. About this time the phenomenon was observed in Persia by Chardin, the traveler. Laplace, Schubert, Poisson and Sir John Herschell regarded the phenomenon with deep interest and sought a satisfactory solution for it. From Sir John Herschell at the Cape of Good Hope came the suggestion that the milky way could be broken up into well-defined sections and that with sufficiently powerful telescopes all its nebulae could be resolved into stars. Humboldt himself directs attention to so-called "starless openings" in the milky way through which one looks out into empty space.
Before Humboldt died there were a large number of competent observers of terrestrial phenomena. It was taken for granted as needing no proof that the interior of the earth is liquid and of high temperature, and that this heated melted matter has acted, and continues to act, upon the surface of the earth. It was believed that the depths of the sea correspond in general with the heights of the mountains, and that our power to study the surface of the earth is limited to about the distance of 48,000 feet. The history of volcanoes, traced from the days of Plato, Aristotle, Ovid, Pliny to Daubeny, whose treatise on the subject (Paris, 1848) Humboldt accepts as the best ever written, leads him to propound opinions of his own and to compare them with suggestions made by Darwin in his account of his cruise in the ship Beagle. He places a high estimate on the value of the measurements by the pendulum of Sir Edward Sabine as a means of determining the figure of the earth. From his voyage in 1822 and 1823 much was learned about magnetism in general and terrestrial magnetism in particular. To the establishment of what were deemed by Humboldt sound theories concerning the internal heat of the earth, Fourier, Biot, Laplace and Poisson made large contributions. The mathematical calculations of Friedrich Gauss and Weber were accepted as of the first importance in the study of magnetism. The oscillations of the magnetic needle were observed and noted in different parts of the world. Humboldt himself says in a note. Vol. I., p. 187: "I regard the discovery of the law of the decrement of magnetic force from the poles to the equator as the most important result of my American voyage." The subject arrested the attention of the British Association, which made special arrangements for its careful study. While living at Quito, Humboldt gave what he deemed first-hand study to the nature and cause of earthquakes and arrived at conclusions which were strengthened, as he believed, by similar studies in the same region by Bousingault, twenty-three years later. Bousingault's treatise on earthquakes, Humboldt accepted as the best and most authoritative ever written. Its theories will hardly be regarded as final by scientists of our time. Eocks, Humboldt declares, without any qualification are in the process of formation and disintegration. He divides them into eruptive, sedimentary, metamorphic and conglomerate rocks. The importance of the subject of paleontology is recognized in "Cosmos," but is treated almost as if it were a new science. Agassiz's work on "Fossil Fishes," in which more than 1,700 species were described, is given the honor it deserves. But open minded as Humboldt was to every suggestion of scientific men and ready to accept any well-authenticated statement, he was very cautious about departures from old and prevailing theories. Since his time, meteorology, as he predicted it would, has become a science of much practical value. Geology, mineralogy and paleontology have made giant strides. Chemistry has almost entirely changed its character, even its terminology has become new. The advance in physics almost defies description. Since Humboldt died Lord Kelvin, Clerk Maxwell of Edinburgh and Herz of Germany have done their epoch-making work on light. Lines of magnetic force and the character of the magnetic field are better understood than when Faraday gave his attention to them and through his discoveries received the warmest praise from Humboldt. Electricity as a science and in its practical applications has developed one might say almost entirely since 1859. Of radium and radio-activity, whose secrets Monsieur and Madame Curie and Rutherford have done so much to make known, Humboldt knew nothing. Nor had he any conception of the character and extent of the revelations from the heavenly bodies which studies in astro-physics have brought. But of science as it was in his day, and for some years after his death, he was a master and as competent as he himself believed and as others admit him to have been to make such general statements concerning its triumphs and promise as to show the careful reader of "Cosmos" even now the foundations upon which the scientific progress of the last half century has rested.
- ↑ "Cosmos," Vols. I.-V., Harper & Brothers, New York.