DIONYSIUS LARDNER, D.C.L.,

Formerly Professor of Natural Philosophy and Astronomy in University College, London

VOL. I.

LONDON:

WALTON AND MABERLY,

UPPER GOWER STREET, AND IVY LANE, PATERNOSTER ROW.

CONTENTS.

THE PLANETS: ARE THEY INHABITED WORLDS?

CHAP. I.-1. Aspect of the firmament.-2. Direct evidence on this

question not obtained by the telescope.-3. Telescope diminishes

distance.-4. Evidence from analogy extremely cogent.-5. Con-

sideration of the terrestrial planets.-6. Circumstances which

render the earth habitable.-7. Like circumstances to be looked

for in the planets. - 8. Similarity of position and motion of

terrestrial planets.-9. Uniformly supplied with light and heat.

-10. Objection of inequality of distance answered.-11. By the

effect of atmosphere.-12. Different degrees of light on the planets.

-13. Structure of the eye.-14. Its adaptation to different dis-

tances.-15. Adaptation of strength of organised creatures to

their weight.-16. Adaptation of the rotation of the earth to this

organisation.-17. Floral clock of Linnæus.-18. Time of rotation

not the consequence of a physical law.-19. Rotation of the other

planets.-20. Of Mars.-21. Of Venus and Mercury.-22. Their

close analogy to the earth.-23. Inclination of the earth's axis.

-24. Produces the seasons.-25. Like provision in the other

planets.-26. The atmosphere

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CHAP. II.—1. Uses of an atmosphere-colour of sky.-2. Its effects

on temperature. 3. Planetary atmospheres observable. -4.

Clouds visible in them.-5. Hence rain, hail, and snow.-6.

Winds manifested on the planets.-7. Clouds on Mercury, Venus,

and Mars.-8. Continents and oceans.-9. Effect of gravity on

planets.-10. Its relation to organised beings.-11. Adaptation

of organised beings to the force of gravity.-12. Gravity on

Mercury, Venus, and Mars.-13. Solar system.-Planets.-14.

Number of planets-groups.-15. Inner group-the twenty-five

grouped round the sun.-16. The outer group-Jupiter, Saturn,

Uranus, and Neptune.-17. Their distances from the sun, from

each other, and from the earth.-18. Apparent diameters of Sun's

disk as seen from these planets-Sun's light and heat.-19.

Question of habitability of these planets considered in reference

to sun's light and heat.-20. Great comparative magnitude of

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