For his work in natural history, Aristotle was powerfully supported by one of the most resplendent military geniuses that the world has ever seen, Alexander the Great. To this prince and warrior, when he was a lad, the philosopher had discharged the office of private teacher. It would appear that either Aristotle was courtier enough, or young Alexander was man enough, to make this relation a pleasant one to the boy. For, in later years, the conqueror of the world presented to his former teacher a round million of dollars to make himself comfortable withal. But who can tell which it was, gratitude for benefit received, or remorse for trouble occasioned, that prompted the _ex post facto_[3] royal munificence? Perhaps it was both—a tardy gratitude quickened by a generous remorse. The chief glory of Aristotle is to have at once invented and finished the science of logic. For this is an achievement which may justly be credited to the philosopher of Stagirus. It would generally be conceded that, since Aristotle’s day, little or nothing substantial has been added to the results of his labor in the field of pure logic. The name Orˈga-non (instrument) is not Aristotle’s word, but that of some ancient editor of his works. It is a noteworthy name, as having dictated to Bacon the title to his epoch-making work, the _Novum Organum_ (the new method or instrument). It would not be easy to give an exhaustive account of Aristotle’s productions, and make the account attractive reading. We shall not undertake so impracticable a task. Let our readers accept our word for it that Aristotle, though a justly renowned name in the history of thought, is not fitted to be a popular author. From his “History of Animals” we present a specimen extract that will perhaps with some readers go far toward confuting what we just now said. There are, we confess, some things in this treatise that read almost as if they might belong to that truly fascinating book, “Goldsmith’s Animated Nature:” “The cuckoo is said by some persons to be a changed hawk, because the hawk which it resembles disappears when the cuckoo comes, and indeed very few hawks of any sort can be seen during the period in which the cuckoo is singing, except for a few days. The cuckoo is seen for a short time in the summer, and disappears in winter. But the hawk has crooked talons, which the cuckoo has not, nor does it resemble the hawk in the form of its head, but in both these respects is more like the pigeon than the hawk, which it resembles in nothing but its color; the markings, however, upon the hawk are like lines, while the cuckoo is spotted.