On the earth we find animated existence confined to the surface of the crust of the globe, to the lower and denser strata of the atmosphere, and to the film of water that constitutes the oceans. It does not exist in the heart of the rocks forming the body of the planet nor in the void of space surrounding it outside the atmosphere. As the earth condensed from the original nebula, and cooled and solidified, a certain quantity of matter remained at its surface in the form of free gases and unstable compounds, and, within the narrow precincts where these things were, lying like a thin shell between the huge inert globe of permanently combined elements below, and the equally unchanging realm of the ether above, life, a phenomenon depending upon ceaseless changes, combinations and recombinations of chemical elements in unstable and temporary union, made its appearance, and there only we find it at the present time. It is because air and water furnish the means for the continual transformations by which the bodies of animals and plants are built up and afterward disintegrated and dispersed, that we are compelled to regard their presence as prerequisites to the existence, on any planet, of life in any of the forms in which we are acquainted with it. But if we perceive that another world has an atmosphere, and that there is water vapor in its atmosphere--both of which conditions are fulfilled by Venus--and if we find that that world is bathed in the same sunshine that stimulates the living forces of our planet, even though its quantity or intensity may be different, then it would seem that we are justified in averring that the burden of proof rests upon those who would deny the capability of such a world to support inhabitants. The generally accepted hypothesis of the origin of the solar system leads us to believe that Venus has experienced the same process of evolution as that which brought the earth into its present condition, and we may fairly argue that upon the rocky shell of Venus exists a region where chemical combinations and recombinations like those on the surface of the earth are taking place. It is surely not essential that the life-forming elements should exist in exactly the same states and proportions as upon the earth; it is enough if some of them are manifestly present. Even on the earth these things have undergone much variation in the course of geological history, coincidently with the development of various species of life. Just at present the earth appears to have reached a stage where everything contributes to the maintenance of a very high organization in both the animal and vegetable kingdoms.