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Ridpath's history of the world; being an account of the ethnic origin, primitive estate, early migrations, social conditions and present promise of the principal families of men .. . TER—SHOWINGTHE ZONE OF THE ASTEROIDS. earth and Mars, between which manyanalogies are discoverable. Of the twothe earth is, doubtless, considerablyolder than the other, as world-age ismeasured by the manifestations of lifethereon. This is to say that the earthand Mars gave off their excessive heatand were cooled sufficiently to admit ofvegetable and animal life at an age farearlier than in the case of any of theot
Ridpath's history of the world; being an account of the ethnic origin, primitive estate, early migrations, social conditions and present promise of the principal families of men .. . TER—SHOWINGTHE ZONE OF THE ASTEROIDS. earth and Mars, between which manyanalogies are discoverable. Of the twothe earth is, doubtless, considerablyolder than the other, as world-age ismeasured by the manifestations of lifethereon. This is to say that the earthand Mars gave off their excessive heatand were cooled sufficiently to admit ofvegetable and animal life at an age farearlier than in the case of any of theother planets. Drawing our analogiesfrom the forms of life with which we arefamiliar, it is quite certain that Jupiter 60 GREAT RACES OF MANKIND. and Saturn have not yet reached the life-bearing epoch. That they will at lengthreach a stage of worldhood at which ani-mate beings can exist upon their surfaceand in their waters can not be little can it be doubted that in courseof time the earth and Mars will lose theconditions under which life can be per-petuated. In that event we may be surethat the epoch of life will cease in ourown planet, though the earth, as such,. JUPITER—A PLANET NOT YET ARRIVED AT THE EPOCH OF LIFE. may continue to occupy its place indefi-nitely in the solar .system. The thing to be granted from the con-sideration of these facts is that all worldsEpoch of Life is have a planet life, and that,SSfSStf* ^ connection with thisplanet life. planet life, at a certain stage thereof life proper becomes toler-able in the given sphere. With thisevent the Epoch of Life begins and runsparallel with the history of the givenworld until the conditions of the latter are so changed as to prevent the furtherpropagation or existence of life upon that, as in the probable case of oursecondary, the Moon, the given orb be-comes a dead world, though still obeyingthe physical laws under which its placeand motions have been hitherto deter-mined. Let us, then, br
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Keywords: ., bookcentury1800, bookdecade1890, booksub, booksubjectworldhistory