INTRODUCTION.
The subject of these lectures is Geography in its most enlarged and comprehensive sense. It will be necessary to preface them with some general observations, which shall serve to indicate the scientific basis on which the discussion will rest. Our starting-point will be with Nature herself and not with arbitrary geographical systems hitherto constructed.
By the word Nature will be meant the entire Creation. The grasping of Nature in all its objects and all its forces becomes, in conjunction with the agency of Time and Space, the comprehension of a great system. The inanimate creation may be represented under the term inorganic, the animate creation under the term organic. Yet there is not an absolute contrast between them; for in both there is ceaseless progress, no pause, but in a higher and comprehensive sense a cosmical life, the whole forming one great Organism, in which the inorganic world, so called, is only the foundation on which the animate creation stands.
To us, our own Earth is the most marked feature of Nature viewed on its inorganic side. To us it is the planet best known of all, or rather the only one closely known, the point whence we draw conclusions on the whole Universe, the resting ground for the glass that searches the Kosmos, to use Humboldt’s word, discerning the place which the Earth holds in it, and prying into the mysteries of the entire creation. Our globe is one of the major planets of our system, all of which gird the sun with great elliptic orbits, midway in which is our own. There begins the first popular division of the planets,—those that are within and those which are without our own orbit. This is one of the most simple of discriminations, one which we inherit from the ancients in an unmodified form. Humboldt retains this primary classification.
The external planets are those whose orbits embrace that of the Earth within their own. The minor planets are those whose orbits are embraced by that of the Earth. These are Mercury and Venus.
The ancients, counting both the sun and moon, reckoned only seven planets. At the end of the eighteenth century another was added, Uranus, an external planet. Through the instrumentality of improved telescopes, soon after, four minor ones were discovered, Ceres, Pallas, Juno, and Vesta; and by the still more perfect lenses recently introduced, and the assiduity and skill of astronomers, the number of these little planetary bodies, ranging between the orbits of Mars and Jupiter, has grown great. Beyond Saturn and Uranus is Neptune, discovered mathematically by Le Verrier, in Paris, and seen by Galle in Berlin, the 23d of September, 1846.
To these (now eighty) planets may be added the twenty to thirty moons of our solar system, and a number of comets.
The middle position of the Earth’s orbit is not without its consequences. The distance of the Earth from the Sun is, in round numbers, 92,000,000 of miles, nearly three times as far as that of Mercury, the planet nearest the Sun. Jupiter, on the other hand, is five times as far from the Sun as the Earth; Uranus about nineteen times as far, and Neptune about thirty-three times as far.
The time of the Earth’s revolution around the Sun is also equally removed from the extremes; its year is 365 days; Mercury’s being 87 days; Jupiter’s 11 of our years; Uranus 84 years; and Neptune’s 165 years.