NEWS FROM JUPITER. 439 



tre. Now, we know that the sun is intensely hot because we feel the 

 heat that he emits, and recognize the intense lustre of his photosphere ; 

 so that we are not in danger of overlooking this important circum- 

 stance in his condition. Jupiter gives out no heat that we can feel, 

 and assuredly Jupiter does not emit an intense light of his own. But, 

 when we find that difficulties, precisely corresponding in kind, though 

 not in degree, to those which we should encounter if we discussed the 

 sun's condition in forgetfulness of his intense heat, exist also in the 

 case of Jupiter, it appears manifest that we may safely adopt the con- 

 clusion that Jupiter is intensely heated, though not nearly to the same 

 degree as the sun. 



We have thus been led by a perfectly distinct an independent 

 line of reasoning to the very conclusion which I have advocated else- 

 where on other grounds, viz., that Jupiter is in fact a miniature sun 

 as respects heat, though emitting but a relatively small proportion of 

 light. I would invite special attention to the circumstance that the 

 evidence on which this conclusion had been based was already cumu- 

 lative. And now a fresh line of evidence, in itself demonstrative I 

 conceive, has been adduced. Moreover, I have not availed myself of 

 the argument, very weighty in my opinion, on which Mr. Mattieu 

 Williams has based similar conclusions respecting the temperature of 

 Jupiter, in his interesting and valuable work called " The Fuel of the 

 Sun." I fully agree with him in regarding it as a reasonable assump- 

 tion, though I cannot go so far as to regard it as certain, that every 

 planet has an atmosphere whose mass corresponds with, or is even 

 perhaps actually proportional to, the mass of the planet it surrounds. 

 If we make such an assumption in the case of Jupiter, we arrive at 

 conclusions closely resembling those to which I have been led by the 

 above process of reasoning. 



Thus many lines of evidence, and some of them absolutely demon- 

 strative, in my opinion, point to the conclusion that Jupiter is an orb 

 instinct with fiery energy, aglow it may well be with an intense light 

 which is only prevented from manifesting itself by the cloudy envel- 

 ope which enshrouds the planet. 



But, so soon as we regard the actual phenomena presented by 

 Jupiter in the light of this hypothesis, we find the means of readily 

 interpreting what otherwise would appear most perplexing. Chief 

 among the phenomena thus accounted for, I would place the recent 

 color-changes in the equatorial zone of Jupiter. 



What, at a .first view, could appear more surprising than a change 

 affecting the color of a zone-shaped region whose surface is many times 

 greater than the whole surface of our earth. It is true that a brief 

 change might be readily explained as due to such changes as occur in 

 our own air. Large regions of the earth are at one time cloud-covered, 

 and at another free from clouds. Such regions, seen from Venus or 

 Mercury, would at one time appear white, and at the other would 



