Note 7 — Chapter IX

A difficulty may be raised, founded on what we may suppose to be the fact, as to the extreme cold of those regions of the Solar System. It may be supposed that water under such a temperature could exist in no other form than ice. And that the cold must there be intense, according to our notion, there is strong reason to believe. Even in the outer regions of our atmosphere, the cold is probably very many degrees below freezing, and in the blank and airless void beyond, it may be colder still. It has been calculated by physical philosophers, on grounds which seem to be solid, that the cold of the space beyond our atmosphere is 100° below zero. The space near to Jupiter, if an absolute vacuum, in which there is no matter to receive and retain heat emitted from the Sun, may, perhaps, be no colder than it is nearer the Sun. And as to the effect the great cold would produce on Jupiter's watery material, we may remark, that if there be a free surface, there will be vapor produced by the Sun's heat; and if there be air, there will be clouds. We may add, that so far as we have reason to believe, below the freezing point, no accession of cold produces any material change in ice. Even in the expeditions of our Arctic navigators, a cold of 40° below zero was experienced, and ice was still but ice, and there were vapors and clouds as in our climate. It is quite an arbitrary assumption, to suppose that any cold which may exist in Jupiter would prevent the state of things which we suppose.