190 LIGHT SCIENCE FOR LEISURE HOURS. 



The existence of well-defined belts is proof positive 

 of the existence of different rates of rotational motion. 

 For instance, we cannot explain our own trade-wind 

 zones, without taking into account the different veloci- 

 ties due to rotation near the equator and in high 

 latitudes matter flowing towards the equator lags 

 behind, matter flowing from it travels in advance, and 

 in either case zones are formed. If a similar explana- 

 tion could be given of the belts of Saturn and Jupiter 

 doubtless they would be accounted for. But where are 

 we to find the varieties of heat in various latitudes of 

 either planet which could account for the multitu- 

 dinous belts sometimes seen ? or how, if the sun's slow 

 action on these remote and large planets were in ques- 

 tion, could we account for the rapid formation and 

 dissipation of cloud-belts ? The largeness of these 

 planets is a point of importance to the argument, 

 because the larger a planet the less, cceteris paribus, is 

 the variation of temperature for any given difference 

 of latitude measured as a distance in miles. If then 

 we cannot look for the required differences of rotational 

 velocity where we find them in our earth's case, it is 

 clear we must turn to difference of rotational velocity on 

 account of difference of distance from the axis, not at 

 places in different latitudes, but in places at different 

 levels. In other words, we must conceive that tinder 

 the action of the planet's intense heat vaporous dis- 

 turbances of the nature of uprush and downrush are 

 continually taking place. Matter rushing upwards 

 from low levels to high levels, where the rate of rota- 



