Assuming that in the progress of this subsidence local centres of condensation subordinate to the general tendency would not be wanting, he conceived that in this way solid nuclei might arise whose local gravitation still further condensing, and so absorbing the nebulous matter each in its immediate neighbourhood, might ultimately become stars, and the whole nebula finally take on the state of a cluster of stars. Among the multitude of nebulae revealed by his telescope every stage of this process might be considered as displayed to our eyes, and in every modification of form to which the general principle might be conceived to apply. The more or less advanced state of a nebula towards its segregation into discrete stars, and of these stars themselves towards a denser state of aggregation round a central nucleus, would thus be in some sort an indication of age. ALEXANDER VON HUMBOLDT Cosmos, a Sketch of the Universe Frederick Henry Alexander von Humboldt was born in Berlin on September 14, 1769. In 1788 he made the acquaintance of George Forster, one of Captain Cook's companions, and geological excursions made with him were the occasion of his first publications, a book on the nature of basalt. His work in the administration of mines in the principalities of Bayreuth and Anspach furnished materials for a treatise on fossil flora; and in 1827, when he was residing in Paris, he gave to the world his "Voyage to the Equinoctial Regions of the New Continent," which embodies the results of his investigations in South America. Two years later he organised an expedition to Asiatic Russia, charging himself with all the scientific observations. But his principal interest lay in the accomplishment of that physical description of the universe for which all his previous studies had been a preparation, and which during the years 1845 to 1848 appeared under the comprehensive title of "Cosmos, or Sketch of a Physical Description of the Universe." Humboldt died on May 6, 1859. _I.--The Physical Study of the World_ The natural world may be opposed to the intellectual, or nature to art taking the latter term in its higher sense as embracing the manifestations of the intellectual power of man; but these distinctions--which are indicated in most cultivated languages--must not be suffered to lead to such a separation of the domain of physics from that of the intellect as would reduce the physics of the universe to a mere assemblage of empirical specialities. Science only begins for man from the moment when his mind lays hold of matter--when he tries to subject the mass accumulated by experience to rational combinations.