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PHILOSOPHICAL PERIODICALS. 561 principles of mathematics, both extremely interesting but not readily lending themselves to condensation. They are : G. Lechelas, L'Axiome de libre rnobilite, and B. Russell, Les Axioines Euclidiens sont-ils empiriques ? REVUE NEO-SCOLASTIQUE. No. 20. J. Huys (' La notion de substance dans la philosophic contemporaine et dans la philosophic scolastique ') examines the notions of substance as found hi the various systems of philosophy that are dominated by the influence of Kant, and compares them with the notion of substance as understood by scholasti- cism. He contends for the reality of substance, not only in the external world, where Wundt would allow its reality, but also in the internal world, where Wundt would deny it. He maintains that, besides the transitory phenomena of the Ego, there is in the Ego something per- manent, which is the subject in which and by which the phenomena are produced. The soul, then, is not "the sum of psychical activities," as Wundt would say ; nor " the ensemble of vital phenomena " (das ganze Seelenleben), as Paulsen would say ; but is a substance. A. ThieYy ('Qu'est-ce que Va,ri?' suite et fin continuing his examination of the aesthetic formula of Count Tolstoi, "art is the means of transmitting sentiments to man," concludes that if this formula be correct, the cook of a Lucullus must be beyond question the greatest artist the world can know, seeing that such a one has the power of exciting to an illimitable extent that appetite which is the most universal of all sensations. D. Nys (' La nature du compose chimique ' suite et fin) refuses to believe that bodies chemically compounded are nothing more than mere aggre- gates of elementary substances, and maintains that, on the contrary, these compounds are actuated by an essential unity. Dr. St. George IVCvart (' L'utilit^ explique-t-elle les caracteres specifiques ? '), basing his conclusion on a lengthened study of the Lories, or brush-tongued parrots, argues that to say with Dr. Alfred W. Wallace that all the dis- tinctive characteristics of species can be accounted for by their utility, is to say what is not merely uncertain, but also improbable. Q. De Graene ('La croyance au monde exterieur') upholds the scholastic theory as to the externality of the world in opposition to idealist ideology on the one hand and positive ideology on the other. ZEITSCHKIFT FUR PSYCHOLOGIE UND PHYSIOLOGIE DER SINNESORGANE. Bd. xx., Heft 4 und 5. K. Zindler. ' Ueber rauinliche Abbildungen des Continuums der Farbenempfindungen und seine mathematische Behand- lung.' [Locality and colour are the only experiences of ordinary life that form continuous manifolds of several dimensions (Riemann). A theoretical discussion of the colour-figure is needed; the experiments necessary for its actual construction have not yet been made. Defini- tion of a psychological colour figure ; requirements of continuity, distance and direction. The historical figures : Newton, Mayer, Lambert, Runge ; the recent figures of Hofler and Ebbinghaus. Maxwell's colour-triangle. The possibility of such two-dimensional figures proves that the con- tinuum of colour- sensations is not more than tridirnensional. Hering's proof of Newton's law of colour-mixture simplified. One-dimensional colour continua : shortest lines, lines of constant curvature, lines of con- stant direction, mixture-continua. Substitutive measurement of colour- distances. The arithmetical colour-scheme. Helmholtz' investigation of the shortest colour-lines. Methods of construction of the psychological colour-figure : Hering's Nuancirungsdreieck, Helmholtz' shortest lines. Colour v. geometry in mathematical instruction.] W. Thorner. ' Ein neuer stabiler Augenspiegel mit reflexlosem Bilde.' C. B. Morrey. 36