A GIANT PLANET. 91 



So that these orbs may fairly be regarded as bear- 

 ing the same relation to their primary that Jupiter 

 himself bears to his primary, the sun. It will be 

 seen presently that this consideration is an important 

 one. 



But the great interest of the study of Jupiter resides 

 in the fact that being the nearest of the outer family 

 of planets, the aspect of his globe supplies the best 

 available means for determining the condition of the 

 giant orbs constituting that family. 



The first feature which strikes us in the telescopic 

 aspect of the planet is the presence, of a series of belts, 

 lying parallel to the planet's equator. Usually the 

 equatorial regions are occupied by a broad bright belt, 

 of a creamy white colour, and bordered on the north 

 and south by copper-coloured belts. Beyond these, 

 again, lie alternate bright and dark belts, the dark 

 belts growing more and more bluish in hue as the pole 

 is approached, while the poles themselves are usually 

 of a somewhat decided blue colour in telescopes adapted 

 to display such features to advantage. There are com- 

 monly two or three dark belts on each hemisphere. 



Now, before inquiring into the peculiarities presented 

 by these belts, and into the remarkable changes which 

 have been noted lately in their general aspect, it may 

 be well for us to consider briefly what such belts seem 

 to imply. That they are due to peculiarities in the 

 planet's atmosphere is admitted on all hands. And it 

 has been usual to compare them with the trade-wind 

 zones and the great equatorial calm zone on our earth. 



