IN the Sitzungsberichte der Wiener Akademie der Wissenschaflen, Herr J. Loschmidt has published a treatise on the equilibrium of temperature in a system of heavenly bodies with regard to gravitation, from which we note the following highly interesting details:—“Sir W. Thomson and Clausius simultaneously,1 drew from their researches the surprising conclusion that the whole universe at some definite period, however remote, would infallibly come to an end. First, all ponderous masses in the universe will eventually have united to one enormous heavenly body; and secondly, upon this body all visible motion will have ceased, all forces having changed to mere molecular motion, which in the shape of heat of universally uniform temperature will be spread in this mass. This state of general death will then last eternally.” Herr Loschmidt, in the course of his researches, has arrived at widely different conclusions. He begins by adopting the general view that the sun is in a state of slow progression of cooling, and that the time will unavoidably arrive when his surface will have solidified, long after all his planets have fallen in upon him, and after his upper and partly also his lower strata have assumed very nearly the temperature of the surrounding universal space. But granting that thus a period of rest and death will have arrived for our solar system, Herr Loschmidt maintains, at the same time, that this period cannot be of unlimited duration; the state of things just described can, according to his views, not be a state of equilibrium. “The previous liquid state of the sun has caused a continued mixture of the warmer parts near the centre with the colder ones near the surface. Thus, however, the equilibrium of temperature, which requires a certain increase of temperature towards the interior, was rendered impossible. At the moment of solidification of the external layers the deeper ones will be far colder than the theory of the state of equilibrium demands. Because, according to this theory, the surface should have the temperature of universal space (about − 140° C. according to Pouillet), but this temperature should rapidly increase towards the interior, reaching at the centre the enormous figure of 250,000,000° C. And it is just because at the moment of the beginning of solidification of the sun no such distribution of temperature took place in the interior, that the state above referred to cannot be of eternal duration. During an extremely long period, in spite of the low temperature of his surface, the solidifying sun will constantly absorb radiant heat from the store in the universe and will concentrate this heat in his interior. We suppose, for a moment, that it would be physically possible that this process of absorption is carried on to the end without the inclosed and dissociated gases in the interior breaking through the solidified surface or crust on account of their enormous tension. We then calculate the amount of heat accumulated in the end and find that it would easily suffice to raise the entire solar mass to 2/5ths of that temperature which the state of equilibrium demands at the centre, viz,, to 100,000,000° C, This figure is raised if the average molecule of the solar mass, instead of being supposed to be of the density of oxygen, is taken to be of the density of carbonate of lime; in that case it would be 125,000,000° C. We may compare these results to the quantity of heat which was produced during the condensation of the solar system from the cosmical nebula, according to the theory of Laplace and Kant. Helmholtz has calculated that the heat thus generated would suffice, to raise the solar mass to a temperature of 28,611,000° C., if it is supposed to have the heat capacity of water. If, instead of water, other substances are taken as starting points, this temperature is considerably raised; so in the case of carbonate of lime or silicic acid, the heat capacity of which is o.2, the resulting temperature would be 140,000,000° C.