94 THE BORDERLAND OF SCIENCE. 



reduced. Now it cannot but be regarded as a remark- 

 able circumstance that, though the sun supplies Jupiter 

 with only one twenty-seventh part of the heat which 

 we receive, there should yet be raised from the oceans 

 of Jupiter such masses of clouds as to form veritable 

 zones; and that, moreover, above these clouds there 

 should be so large a quantity of invisible aqueous 

 vapour that the spectroscopist can recognise the bands 

 of this vapour in the planet's spectrum. 



Even more perplexing is the circumstance that the 

 cloud-masses should form themselves into zones. We 

 cannot get rid of this difficulty by a mere reference to 

 the planet's rapid rotation, unless we are prepared to 

 show how this rotation is to act in forcing the cloud- 

 masses to become true belts. The whole substance of 

 Jupiter and his whole atmosphere must take part in his 

 rotation, and to suppose that aqueous vapour raised 

 from his oceans would be left behind in the upper air 

 like the steam from a railway-engine, is to make a 

 mistake resembling that which caused Tycho Brahe to 

 deny the rotation of the earth, because bodies projected 

 into the air are not left behind by the rotating earth. 

 Nor is it conceivable that belts which vary remarkably, 

 from time to time, in position and extent, should be 

 formed by sun-raised clouds in the Jovian atmosphere, 

 if the planet's surface is divided into permanent lands 

 and seas. 



But we are thus led to consider a circumstance 

 which, as it appears to us, disposes finally of the idea 

 that in the cloud-rings of Jupiter we have to deal 



