The representatives of the theory of entropy are quite correct as long as they confine themselves to distinct processes, in which, _under certain conditions_, the latent heat cannot be reconverted into work. Thus, for instance, in the steam-engine the heat can only be converted into mechanical work when it passes from a warmer body (steam) into a cooler (water); the process cannot be reversed. In the world at large, however, quite other conditions obtain--conditions which permit the reconversion of latent heat into mechanical work. For instance, in the collision of two heavenly bodies, which rush towards each other at inconceivable speed, enormous quantities of heat are liberated, while the pulverized masses are hurled and scattered about space. The eternal drama begins afresh--the rotating mass, the condensation of its parts, the formation of new meteorites, their combination into larger bodies, and so on. II.--MONISTIC GEOGENY The history of the earth, of which we are now going to make a brief survey, is only a minute section of the history of the cosmos. Like the latter, it has been the object of philosophic speculation and mythological fantasy for many thousand years. Its true scientific study, however, is much younger; it belongs, for the most part, to the nineteenth century. The fact that the earth is a planet revolving round the sun was determined by the system of Copernicus (1543); Galilei, Kepler, and other great astronomers, mathematically determined its distance from the sun, the laws of its motion, and so forth. Kant and Laplace indicated, in their cosmogony, the way in which the earth had been developed from the parent sun. But the later history of the earth, the formation of its crust, the origin of its seas and continents, its mountains and deserts, was rarely made the subject of serious scientific research in the eighteenth century, and in the first two decades of the nineteenth. As a rule, men were satisfied with unreliable conjectures or with the traditional story of creation; once more the Mosaic legend barred the way to an independent investigation.