198 LIGHT SCIENCE FOR LEISURE HOURS. 



known facts appear to afford any argument of force,, 

 should replace the ordinary theory, originated in a 

 haphazard way, and in whose favour no single argument 

 of weight has ever been adduced. Since it appears 

 (1) that if the accepted theory of the development of 

 our system is true, the large planets must of necessity 

 be far younger, that is hotter, than our earth and other 

 small planets ; (2), that if made of similar materials, 

 those planets must of necessity be far denser than they 

 actually are, unless they are very much hotter than 

 the earth ; (3), that the atmospheres (judging of their 

 depth from the planets' appearance) would be com- 

 pressed into solid and very dense matter under the 

 planets' attraction unless exceedingly hot throughout 

 their lower layers ; (4), that the belts and their changes 

 imply the uprush and downrush of heated masses of 

 vapour through enormous depths of atmosphere ; (5), 

 that the cloud-belts neither change with the progress 

 of the day nor of the year in the large planets, but in 

 a manner in no way referrible to the sun, and are 

 therefore presumably raised by the intense heat of the 

 planet's own substance ; (6), that so remarkable are the 

 changes taking place in the atmospheres of Jupiter 

 and Saturn, as appreciably (even at our enormous 

 distance) to affect the figure of those planets ; and 

 (7), that the planets shine with more than 2 times the 

 brightness they would have if their visible surface were 

 formed of even so lustrous a substance as white sand- 

 stone I think the conclusion is to all intents and 

 purposes demonstrated that the planets Jupiter and 



