THE PLANETS, ARE THEY INHABITED ? 



1. CONCLUSIVE and satisfactory observations of tins kind have 

 not yet been made on Uranus, but from the observations, imper- 

 fect as they are which have been made, there are probable 

 grounds for the inference that this planet also revolves on an 

 axis in nine hours and a half. 



Thus it appears that these vast globes, revolving at distances 

 from the sun from five to thirty times that of the earth, have 

 like the earth alternations of light and darkness ; that they have 

 days and nights ; that all parts of their surfaces are in turn, like 

 those of the earth, presented to the common centre of light and 

 warmth, but that the intervals which regulate these alternations, 

 " the division of the light from the darkness," which has been 

 found good by Divine beneficence for the races which inhabit the 

 earth, has not been found " good " for those which inhabit those 

 more remote worlds. The average length of the day on them is 

 about five hours, while it is twelve upon the earth. 



The creatures placed upon these planets must, therefore, be so 

 constituted as to require more frequent intervals for rest and 

 sleep, and shorter periods of wakefulness, activity, and labour, 

 than those which inhabit the earth. 



2. The position of the axis of rotation has been ascertained in 

 the cases of Jupiter and Saturn, but not as yet of the other two 

 planets of this group. 



The axis of Jupiter is inclined to the plane of its orbit at the 

 very small angle of 3 5' 30", while that of the earth, as is well 

 known, has an inclination of 23 28' 30". 



As this inclination limits the temperature of the seasons, the 

 extent of the zones and the varieties of the climates, it follows, 

 that on Jupiter these phenomena must be very different from 

 those of the earth, The extreme variation of the altitude of the 

 sun at noon does not much exceed six degrees in any latitude, a 

 change which cannot produce any very sensible variation in the 

 temperature of the seasons. On this planet there is, therefore, 

 perpetual spring. 



3. The tropics of Jupiter are only three degrees north and 

 south of his equator, and the polar circles, which include the only 

 parts of the planet at which the sun remains at any time below 

 or above the horizon during a complete revolution, are limited to 

 three degrees around the poles. 



In fine, the diurnal phenomena on Jupiter are, at all times, 

 nearly the same as they are upon the earth at the Equinoxes. 



4. The case is very different with Saturn, which presents a closer 

 analogy to the earth. The direction of the diurnal motion, in 

 the case of that planet, makes an angle of 26 48' 40", with the 

 plane of the orbit differing little from the angle which the ecliptic 



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