Discussions on climate and cosmology / by James Croll.

  • James Croll
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: Discussions on climate and cosmology / by James Croll. Source: Wellcome Collection.

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    the metal the nearer would its position be to the centre of the mass, and the lighter the metalloid the nearer to the outside. As a general rule the dissociated elements would arrange themselves according to their densities; and it is for this reason, he considers, that the outer planets Neptune, Uranus, Saturn, and Jupiter, are less dense than the inner planets, since they must have been formed chiefly of metalloids, while the inner and more dense planets would consist chiefly of metallic elements. The hypothesis, says Mr. Lockyer, is almost worthless unless we assume very high temperatures, because unless you have heat enough to give perfect dissociation, you will not have that sorting-out which always seems to follow the same law. But the heat which produced this dissociation previous to the forma- tion of the planets could not have been derived from the condensation of the nebula; for the quantity so derived prior to the existence of the outermost planet must have been infinitesimal indeed. The heat exist- ing in the nebula previous to condensation must have come from some other source; and we can conceive of no other save that which we have been considering. The Gaseous State the first Condition of a Nebula.— If the foregoing be the true explanation of the origin of nebulae, it will follow that the gaseous state will in most cases be the first or original condition, and that a nebula giving a continuous spectrum will only be found after it has condensed to a considerable extent. The irresolvable nebulae which exhibit bright lines, in all probability consist, as Mr. Huggins maintains, of glowing gas without anything solid in them. In short, they are nebulae in their first stage of development, and have not as yet condensed sufficiently to become possessed of nuclei. If we adopt the generally accepted