M. Helmholtz, the author of this ingenious theory, has also calculated that "the mechanical force equivalent to the mutual gravitation of the particles of the nebulous mass would have been originally equal to 454 times the quantity of mechanical force actually disposable in our system," 453/454 of the force coming from the conatus to the gravitation would therefore have been already expended. The author adds that the 1/454 which remains of this original heat, would suffice to raise the temperature of a mass of water equal to the combined birth of the sun and the planets, to 28,000,000 of degrees centigrade; this is a quantity of heat equal to 2500 times that which would be engendered by the combustion of the entire solar system, supposing it to be turned into a mass of coal. These calculations are, doubtless, most interesting, but their defect is that they rest upon the conception of the sun's nebulosity, an hypothesis which requires closer examination before it ought to be accepted as the basis of so important a deduction. Besides, if the sun were warmed by a physical cause not in action at the present time, his heat, however great it may be estimated to be, must necessarily have been diminishing as long as the sun has been in existence. Now, we repeat that it does not appear that the heat of the sun has ever suffered any diminution. The theory of nebulosity is therefore no more securely founded in principle than the other hypotheses which have preceded it. Thus, we find that neither astronomy nor physical science offers us any satisfactory explanation of the constant maintenance of solar radiation. Common sense tells us that this furnace, constantly in activity, must be as unceasingly fed; but science is as yet unable to discover the nature and source of its aliment. There, where science places nothing, we venture to place something. In our belief solar radiation is maintained by the continuous, unbroken succession of souls, in the sun. These pure and burning spirits are perpetually replacing the emanations perpetually sent through space by the sun, to the globes which surround him. Thus we complete that uninterrupted circle of which we have previously spoken, which binds together all the creatures of nature by the links of a common chain, and attaches the visible to the invisible world. We may venture to put forward this explanation of the maintenance of solar radiation with some confidence, since science can give us no exact information upon the point, and philosophy in this case only fills up the void left by astronomy and physics.