MERCURY, A WORLD OF TWO FACES AND MANY CONTRASTS [18]
Grotesqueness of Mercury considered as a world—Its dimensions, mass, and movements—The question of an atmosphere—Mercury's visibility from the earth—Its eccentric orbit, and rapid changes of distance from the sun—Momentous consequences of these peculiarities—A virtual fall of fourteen million miles toward the sun in six weeks—The tremendous heat poured upon Mercury and its great variations—The little planet's singular manner of rotation on its axis—Schiaparelli's astonishing discovery—A day side and a night side—Interesting effects of libration—The heavens as viewed from Mercury—Can it support life?
[CHAPTER III]
VENUS, THE TWIN OF THE EARTH [46]
A planet that matches ours in size—Its beauty in the sky—Remarkable circularity of its orbit—Probable absence of seasons and stable conditions of temperature and weather on Venus—Its dense and abundant atmosphere—Seeing the atmosphere of Venus from the earth—Is the real face of the planet hidden under an atmospheric veil?—Conditions of habitability—All planetary life need not be of the terrestrial type—The limit fixed by destructive temperature—Importance of air and water in the problem—Reasons why Venus may be a more agreeable abode than the earth—Splendor of our globe as seen from Venus—What astronomers on Venus might learn about the earth—A serious question raised—Does Venus, like Mercury, rotate but once in the course of a revolution about the sun?—Reasons for and against that view
[CHAPTER IV]
MARS, A WORLD MORE ADVANCED THAN OURS [85]
Resemblances between Mars and the earth—Its seasons and its white polar caps—Peculiar surface markings—Schiaparelli's discovery of the canals—His description of their appearance and of their duplication—Influence of the seasons on the aspect of the canals—What are the canals?—Mr. Lowell's observations—The theory of irrigation—How the inhabitants of Mars are supposed to have taken advantage of the annual accession of water supplied by the melting of the polar caps—Wonderful details shown in charts of Mars—Curious effects that may follow from the small force of gravity on Mars—Imaginary giants—Reasons for thinking that Mars may be, in an evolutionary sense, older than the earth—Speculations about interplanetary signals from Mars, and their origin—Mars's atmosphere—The question of water—The problem of temperature—Eccentricities of Mars's moons
[CHAPTER V]
THE ASTEROIDS, A FAMILY OF DWARF WORLDS [129]