How moderate he is in such suppositions as he ventures; how cautious when his persistent patience has at last struck against "the inaccessible wall of the Unknowable"! Then, with admirable frankness, tranquil and sincere, he simply owns that "he does not know," unlike so many others, whose uncritical minds are contented with a fragmentary vision, and run so far ahead of the facts that they can only promote indefinite illusion and error. One is surprised indeed to remark how few even of the most learned and well-informed of men have a real aptitude for observation, and a highly instructive book might be written concerning the discrepancies and the weak points in our knowledge. If they were subjected to a sufficiently severe test, how threadbare would appear many of those problems which nature and the world present, and which are regarded as resolved! How long, for instance, was needed to destroy the legend of the cuckoo, incessantly repeated down to the days of Xavier Raspail, and to us so familiar; to elucidate its history, and to set it in its true light! (7/34.) It is by means of such data as these that a science is founded, for theories decay, and only well-observed facts remain irrefragable. With stones such as these, which are hewn by the great artisan, the structures of the future will be built, and our own science, perhaps, will one day be refashioned. For this reason Fabre's books are an education for all those who wish to devote themselves to observation; a manual of mental discipline, a true "essay upon method," which should be read by every naturalist, and the most interesting, instructive, familiar and delightful course of training that has ever been known.