We know that in speech, heat and life are almost synonymous words. In every language we find it said that persons are _frozen by death_, in _the icy sleep of death_, that _cold is death-like_, &c. This image is an exact expression of the reality. An animal or a plant, when deprived of life is necessarily cold. A shiver is the precursor of every malady, and the sure forerunner of death. Every dead body is a cold body. It may be said that in the animal form cold takes the place of life, as in inanimate bodies cold succeeds to heat. Let us now consider the following facts. It is solely by the prolonged action of heat that plants can germinate, grow, and develop themselves; in order to come to perfection, every plant requires an ascertained number of degrees of heat, and botanists and agriculturists know quite accurately the total number of degrees of heat requisite to ripen their cereals, and make their fruit-trees bear. A prolonged and undisturbed accumulation of heat is indispensable to produce life in the impregnated egg of a bird, so that by employing caloric in a hatching machine, the process of hatching may be artificially perfected. The eggs of viviparous animals are sustained by the heat of the mother's body, and besides, as Hervey says, everything that has life proceeds from an egg (omne vivum ex ovo). If we recall to mind that, after the development of the germ in mammiferous animals, the unvarying maternal heat is indispensable to the formation of the organs of the fœtus, we shall be led to inquire whether heat does not directly produce life, whether heat does not transform itself into vital force. Modern philosophers who have propounded the _Mechanical Theory of Heat_, that is to say the profound and admirable doctrine of the mutual conversion of forces, the professors who have proved by mathematical evidence that heat converts itself into mechanical force, and the converse, might perhaps complete their brilliant synthesis by adding that heat, which converts itself into mechanical force, can also transform itself into life, or into vital force, and that the splendid theory of the transformation of forces does not apply to inanimate bodies only, but finds an astonishing confirmation in animate bodies. Thus heat and life would be the manifestation of one and the same power, and the cause of life would be found to dwell, like the cause of mechanical force, in the sun. [Illustration] FOOTNOTES: [5] Represented by the French word _hectare_. [Illustration] CHAPTER THE EIGHTH. THE SUN THE DEFINITIVE ABODE OF SOULS WHO HAVE ATTAINED THE HIGHEST RANK IN THE CELESTIAL HIERARCHY.--THE SUN THE FINAL AND COMMON DWELLING OF SOULS WHO HAVE COME FROM THE EARTH.--THE PHYSICAL CONSTITUTION OF THE SUN.--THE SUN IS A MASS OF BURNING GASES.