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.