THE PLANET SATURN. 363 



face, and it may not be uninteresting to consider some of their 

 peculiarities. 



In considering the climatic conditions of a planet we find they 

 depend principally upon three factors : the distance of the planet 

 from the sun, the inclination of its axis, and the length of its 

 year, with incidentally the length of its day. What the results 

 of this combination may lead us to expect in the case of Saturn 

 we will point out by using the earth, naturally, for analogy or 

 contrast. 



In the first place, as affecting animal and vegetable life, the 

 greater distance of the sun, and the corresponding decrease in 

 its lighting and heating power compared with the same effects on 

 the earth, would materially change in itself the character of such 

 life on Saturn. As already noted, the heat and light are reduced 

 to nearly one one-hundredth of their intensity here, but no one can 

 tell what compensating features may ultimately be provided for 

 retaining the internal heat of the globe or storing up the sun's 

 heat. As an instance of such adaptation we have only to turn to 

 the planet Mars, where we have visual proof, in the melting of 

 its polar " snows," of a much milder climate than the earth pos- 

 sesses, although the intensity of the sun's heat there is reduced 

 by half. 



In connection with the foregoing is the question of the com- 

 position of the atmosphere, and whether it could support such 

 organisms as we are familiar with in terrestrial life. The spec- 

 troscope has told us but little about Saturn's atmosphere, but it is 

 known that the planet is provided with one of considerable ex- 

 tent, and apparently of a similar constitution to our own. The 

 presence of water vapor has been detected, according to some 

 observers, but not positively ; yet it is fair to suppose from other 

 considerations that this most necessary adjunct of all life is plen- 

 tifully supplied. 



The change in the seasons will, of course, depend upon the in- 

 clination of the axis, which in Saturn's case is twenty-six and 

 a half degrees from the perpendicular to its orbit. When we 

 remember that the corresponding inclination of the earth's axis 

 is twenty-three and a half degrees, it will be apparent that the 

 change of seasons would be quite similar to ours, the sun mere- 

 ly rising three degrees higher in the heavens at the summer 

 solstice and three degrees lower at the winter solstice. But the 

 length of the seasons, determined by Saturn's long journey around 

 the sun, will be, on the average, nearly seven and a half years, a 

 fact which would render unlikely much similarity in organic life 

 to the forms found on the earth. If we add to this the rapid suc- 

 cession of day and night, each being at the equator of but five 

 and a quarter hours' duration, we may look for still further dis- 



