The marvel is that with such scanty data, Heracleitus was able to attain to views which are in truly remarkable harmony with the most advanced theories as to the constitution of matter. Nowadays the very qualities of hardness and impenetrability are being ascribed to motion--to the almost inconceivable rapidity of the whirling of electrons within the system of the atom. Le Bon, for example, in his "Evolution of Matter" and his "Evolution of Forces," contends that atoms are continually breaking down, radium presenting merely an extreme case of a general rule, and that the final product is something which is no longer matter. Robbed of motion, what we call matter disappears! It eludes detection by any methods known to us, and ceases, therefore, so far as we are concerned, to be existent. Atoms, then, according to this modern doctrine, are complex systems of motion; and bodies, all agree, are aggregates of atoms. It seems to follow that the ground of reality, from the point of view of physics, is motion. In short, as Heracleitus taught, the world is the result of ceaseless motion. Tyndall's doctrine of "heat as a mode of motion" is being generalised until it covers the whole field of material phenomena. Or approach the theory of Heracleitus from the side of modern astronomy, the harmony between old and new is equally striking. All substances, said he, spring from fire and to fire they are bound to return. It does not require much special knowledge to realise that this statement contains the pith of the latest theories of the birth and death of worlds. From fire-mist, says the modern astronomer, they were condensed, and to fire-mist, by collisions or otherwise, they will return. What the particular stages may be, what the significance of the nebula;, what the cosmic functions of electricity, and other like problems--may be, and will be, matter for keen debate. But the grand generalisation remains--from fire-mist back again to fire-mist. How modern, also, the grand unity which such a theory gives to existence as a whole. Physics, psychology, sociology, even spiritual facts, all come under the sway of the vast generalisation, because all concerned with the same ultimate Reality. The most striking parallel is found, perhaps, in the doctrine of Energy, which is attracting so much attention at the present time, and of which Ostwald is a champion so doughty. It embodies an attempt to bring into one category the various physical forces together with the phenomena of organic evolution, of psychology, and of sociology in the largest sense. Whether the attempt is successful or not, it is a tribute to the genius of the ancient sage, though it seems to lack that definite element of consciousness, or soul-life, which was so adequately recognised by its great predecessor.