For this purpose he turned his attention to descriptive botany, traversing distant lands and mountain ranges to ascertain with certainty the geographical distribution of plants. He investigated the laws regulating the differences of temperature and climate, and the changes of the atmosphere. He studied the formation of the earth's crust, explored the deepest mines, ascended the highest mountains, and wandered through the craters of extinct volcanoes. He became thoroughly acquainted with chemistry, with astronomy, with terrestrial magnetism; and as the investigation of one subject leads to all others, for the reason that there is a mutual dependence and a necessary connection between all facts, so Humboldt became acquainted with all the known sciences. His fame does not depend so much upon his discoveries (although he discovered enough to make hundreds of reputations) as upon his vast and splendid generalizations. He was to science what Shakespeare was to the drama. He found, so to speak, the world full of unconnected facts--all portions of a vast system--parts of a great machine; he discovered the connection that each bears to all; put them together, and demonstrated beyond all contradiction that the earth is governed by law. He knew that to discover the connection of phenomena is the primary aim of all natural investigation. He was infinitely practical. Origin and destiny were questions with which he had nothing to do. His surroundings made him what he was. In accordance with a law not fully comprehended, he was a production of his time. Great men do not live alone; they are surrounded by the great; they are the instruments used to accomplish the tendencies of their generation; they fulfill the prophecies of their age. Nearly all of the scientific men of the eighteenth century had the same idea entertained by Humboldt, but most of them in a dim and confused way. There was, however, a general belief among the intelligent that the world is governed by law, and that there really exists a connection between all facts, _or that all facts are simply the different aspects of a general fact_, and that the task of science is to discover this connection; to comprehend this general fact or to announce the laws of things. Germany was full of thought, and her universities swarmed with philosophers and grand thinkers in every department of knowledge. Humboldt was the friend and companion of the greatest poets, historians, philologists, artists, statesmen, critics, and logicians of his time.