SOLIDS, LIQUIDS, AND GASES. 385 



riously changed. On Mercury water would rank as one of 

 the condensible gases; on Mars, as a fusible solid; but what 

 on Jupiter? 



Recent observations justify us in regarding this as a 

 miniature sun, with an external envelope of cloudy matter, 

 apparently of partially condensed water, but red-hot, or 

 probably still hotter within. His vaporous atmosphere is evi- 

 dently of enormous depth, and the force of gravitation being 

 on his visible outer surface two and a half times greater than 

 that on our earth's surface, the atmospheric pressure in de- 

 scending below this visible surface must soon reach that at 

 which the vapor of water would be brought to its critical 

 condition. Therefore we may infer that the oceans of Ju- 

 piter are neither of frozen liquid nor gaseous water, but are 

 oceans or atmospheres of critical water. If any fish-birds 

 swim or fly therein they must be very critically organized. 



As the whole mass of Jupiter is three hundred times 

 greater than that of the earth, and its compressing energy 

 towards the centre proportional to this, its materials, if sim- 

 ilar to those of the earth and no hotter, would be consider- 

 ably more dense, and the whole planet would have a higher 

 specific gravity; but we know by the movement of its satel- 

 lites that, instead of this, its specific gravity is less than a 

 fourth of that of the earth. This justifies the conclusion 

 that it is intensely hot, for even hydrogen, if cold, would 

 become denser than Jupiter under such pressure. 



As all elementary substances may exist as solids, liquids, 

 or gases, or critically, according to the conditions of tem- 

 perature and pressure, I am justified in hypothetical!} 7 con- 

 cluding that Jupiter is neither a solid, a liquid, nor a gaseous 

 planet, but a critical planet, or an orb composed internally 

 of dissociated elements in the critical state, and surrounded 

 by a dense atmosphere of their vapors, and those of some 

 of their compounds, such as water. The same reasoning 

 applies to Saturn and the other large and rarefied planets. 



The critical temperature of the dissociated elements of 

 the sun is probably reached at the base of the photosphere, 

 or that region revealed to us by the sun-spots. When I 

 wrote " The Fuel of the Sun," thirteen or fourteen years 

 ago, I suggested, on the above grounds, the then heretical 



