In the same way, if two currents have the same direction and are brought toward one another, it will be necessary, in order to maintain the intensity to supply energy, because the living force will be augmented. We shall, therefore, have to overcome an electromotive force of induction which will tend to diminish the intensity of the currents. It would tend on the contrary to augment it, if the currents had the same direction and were carried apart, or if they had opposite directions and were brought together. Finally, the centrifugal force tends to increase the distance between the balls, which would augment the living force were the angular velocity to be maintained. In like manner, when the currents have the same direction, they attract each other--that is to say, they tend to approach each other, which would increase the living force if the intensity were maintained. If their directions are opposed they repel one another and tend to separate, which would again tend to increase the living force were the intensity kept constant. Thus the electrostatic effects would be due to the elasticity of the ether and the electro-dynamical phenomena to the living force. Now, ought this elasticity itself to be explained, as Lord Kelvin thinks, by rotations of small parts of the fluid? Different reasons may render this hypothesis attractive; but it plays no essential part in the theory of Maxwell, which is quite independent of it. In the same way, I have made comparisons with divers mechanisms. But they are only similes, and pretty rough ones. A complete mechanical explanation of electrical phenomena is not to be sought in the volumes of Maxwell, but only a statement of the conditions which any such explanation has to satisfy. Precisely what will confer long life on the work of Maxwell is its being unentangled with any special mechanical hypothesis. FOOTNOTES: [Footnote 36: Translated from a paper by M. Henri Poincaré.] XXXIV AUGUST WEISMANN 1834-1914 _August Weismann was born at Frankfort-on-Main, January 17, 1834, and studied medicine at Göttingen, 1852-1856. He was physician to the Austrian Archduke for two years (1860-62), but was compelled to retire because of his poor eyesight. He was called to the chair of zoology at Freiburg University. After a close study of Darwin’s theory, he published in 1876 his “Studies in the Theories of Descent,” a book which at once attracted much attention among scientists, for it proposed the theory of the germ-plasm as the basis of heredity, and denied the theory of the transmissibility of acquired characteristics. He died at Freiburg-in-Baden, November 6, 1914._ THE CONTINUITY OF THE GERM-PLASM AS THE FOUNDATION OF A THEORY OF HEREDITY[37] INTRODUCTION