3. Can we see any physical reason, for the fact which appears to us so probable, that all the water and vapor of the system is gathered in its outward parts? It would seem that we can. Water and aqueous vapor are driven from the Sun to the outer parts of the solar system, or are allowed to be permanent there only, as they are driven off and retained at a distance by any other source of heat;--to use a homely illustration, as they are driven from wet objects placed near the kitchen-fire: as they are driven from the hot sands of Egypt into the upper air: as they are driven from the tropics to the poles. In this latter case, and generally, in all cases, in which vapor is thus driven from a hotter region, when it comes into a colder, it may again be condensed in water, and fall in rain. So the cold of the air in the temperate zone condenses the aqueous vapors which flow from the tropics; and so, we have our clouds and our showers. And as there is this rainy region, indistinctly defined, between the torrid and the frigid zones on the earth; so is there a region of clouds and rain, of air and water, much more precisely defined, in the solar system, between the central torrid zone and the external frigid zone which surrounds the Sun at a greater distance. 4. _The Earth's Orbit is the Temperate Zone of the Solar System._ In that Zone only is the play of Hot and Cold, of Moist and Dry, possible. The Torrid Zone of the Earth is not free from moisture; it has its rains, for it has its upper colder atmosphere. But how much hotter are Venus and Mercury than the Torrid Zone? There, no vapors can linger; they are expelled by the fierce solar energy; and there is no cool stratum to catch them and return them. If they were there, they must fly to the outer regions; to the cold abodes of Jupiter and Saturn, if on their way, the Earth did not with cold and airy finger outstretched afar, catch a few drops of their treasures, for the use of plant, and beast, and man. The solid stone only, and the metallic ore which can be fused and solidified with little loss of substance, can bear the continual force of the near solar fire, and be the material of permanent solid planets in that region. But the lava pavement of the Inner Planets bears no superstructure of life; for all life would be scorched away along with water, its first element. On the Earth first, can this superstructure be raised; and there, through we know not what graduation of forms, the waters were made to bring forth abundantly things that had life; plants, and animals nourished by plants, and conspiring with them, to feed on their respective appointed elements, in the air which surrounded them. And so, nourished by the influences of air and water, plants and animals lived and died, and were entombed in the scourings of the land, which the descending streams carried to the bottom of the waters. And then, these beds of dead generations were raised into