Page:Popular Science Monthly Volume 80.djvu/361

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 astrol-