The idea of such a physical description of the universe had, it appears, been present to his mind from a very early epoch. It was a work which he felt he must accomplish, and he devoted almost a lifetime to the accumulation of materials for it. For almost half a century it had occupied his thoughts; and at length, in the evening of life, he felt himself rich enough in the accumulation of thought, travel, reading, and experimental research, to reduce into form and reality the undefined vision that has so long floated before him. The work, when completed, will form three volumes. The 'first' volume comprises a sketch of all that is at present known of the physical phenomena of the universe; the 'second' comprehends two distinct parts, the first of which treats of the incitements to the study of nature, afforded in descriptive poetry, landscape painting, and the cultivation of exotic plants; while the second and larger part enters into the consideration of the different epochs in the progress of discovery and of the corresponding stages of advance in human civilization. The 'third' volume, the publication of which, as M. Humboldt himself informs me in a letter addressed to my learned friend and publisher, Mr. H. G. Bohn, "has been somewhat delayed, owing to the present state of public affairs, will comprise the special and scientific development of the great Picture of Nature p 6 Each of the three parts of the 'Cosmos' is therefore, to a certain extent, distinct in its object, and may be considered complete in itself. We can not better terminate this brief notice than in the words of one of the most eminent philosophers of our own country, that, "should the conclusion correspond (as we doubt not) with these beginnings, a work will have been accomplished every way worthy of the author's fame, and a crowning laurel added to that wreath with which Europe will always delight to surround the name of Alexander von Humboldt." In venturing to appear before the English public as the interpreter of "the great work of our age,"* I have been encouraged by the assistance of many kind literary and scientific friends, and I gladly avail myself of this opportunity of expressing my deep obligations to Mr. Brooke, Dr. Day, Professor Edward Forbes, Mr. Hind, Mr. Glaisher, Dr. Percy, and Mr. Ronalds, for the valuable aid they have afforded me. [footnote] *The expression applied to the Cosmos by the learned Bunsen, in his late Report on Ethnology, in the 'Report of the British Association for' 1847, p. 265.