With the information contained in the preceding chapter, respecting the structure of the earth and its atmosphere, we are now in a condition to compare it as an inhabited world with the other planets of our system, and to ascertain, from the analogies which exist between them, to what extent it is probable that they are either inhabited, or in a state of preparation, as the earth once was, for the reception of inhabitants.

In making this comparison, the first point which demands our attention is the position which the earth occupies in the Solar system. In reference to the number of the planets, which is nine, reckoning the asteroids as one, Jupiter is the fifth, or middle planet, and is otherwise highly distinguished. Our earth, therefore, is neither the middle planet nor the planet nearest the sun, nor the planet farthest from that luminary. In reference to the light and heat which the planets receive from the sun, the Earth has neither the warmest, nor the middle, nor the coldest place. With respect to the number of moons or satellites, the only uses of which that we know, is to give light to the planet, and produce tides in its seas, the Earth has the lowest number, all the planets exterior to it having a larger number.