Of the prodigious total of works composed by Aristotle, I have already mentioned that the larger number have perished. But there still remain about forty treatises, of authenticity not open to any reasonable suspicion, which attest the grandeur of his intelligence, in respect of speculative force, positive as well as negative, systematizing patience, comprehensive curiosity as to matters of fact, and diversified applications of detail. In taking account of these treatises, we perceive some in which the order of sequence is determined by assignable reasons; as regards others, no similar grounds of preference appear. The works called 1. De Coelo; 2. De Generatione et Corruptione; 3. Meteorologica,--are marked out as intended to be studied in immediate succession, and the various Zoological treatises after them. The cluster entitled Parva Naturalia is complementary to the treatise De Animâ. The Physica Auscultatio is referred to in the Metaphysica, and discusses many questions identical or analogous, standing in the relation of prior to a posterior, as the titles indicate; though the title 'Metaphysica' is not affixed or recognized by Aristotle himself, and the treatise so called includes much that goes beyond the reach of the Physica. As to the treatises on Logic, Rhetoric, Ethics, Politics, Poetics, Mechanics, &c., we are left to fix for ourselves the most convenient order of study. Of no one among them can we assign the date of composition or publication. There are indeed in the Rhetorica, Politics, and Meteorologica, various allusions which must have been written later than some given events of known date; but these allusions may have been later additions, and cannot be considered as conclusively proving, though they certainly raise a presumption, that the entire work was written subsequently to those events.