But next, the atmosphere of Jupiter is probably of very great density.  Dr. Huggins states that he has observed in the spectrum of Jupiter “three or four strong lines, one of them coincident with a strong line in the earth’s atmosphere.” [Footnote:  Lecture at Manchester, November 16, 1870.] Strong lines mark increased density in the absorbent medium, and lines hitherto unobserved indicate new elements.  It is therefore probable that the atmosphere of Jupiter is not only much more dense than that of the earth, but also contains some elements—­which are absent from the latter.  When with this fact we connect the very great extent of the atmosphere, it will be evident that the pressure at the surface of the planet will be enormous, and from this we can form an estimate of the intensity of the forces which must be at work in the interior of the planet, to project jets of vapour through such an atmosphere to so great a height.

The link which connects Jupiter with the earth, in the second stage of its existence, is the mention by Moses of the “waters which were above the firmament.”  Viewed in the light of the present condition of the earth such a notice seems unaccountable.  But if the earth at that time were in a condition similar to that in which Jupiter appears to be now, the water in the atmosphere or above the firmament would be a very important element in any description that might be given of it.  It is in fact most probable that all the water (in the strict sense of the word) then in existence would be in a state of vapour, and that the waters which were under the firmament were the molten materials which afterwards formed rocks and ores, since, as has been already noticed, the word is the only one which could be employed to describe fluids in general.

We may now try to form some idea of the probable state of the earth at this period.  Its centre would be occupied by a fused mass, in which were blended all the more intractable solid constituents of the present world.  This would be surrounded by an atmosphere of very great height and density, containing not only all the present constituents of air, but also all, or nearly all, the water, and all the more volatile of the metals and other elements.  Carbonic acid, to a very large extent, would probably be present, and a very considerable proportion of the oxygen which now exists in combination with various bases, and forms by weight so large a proportion of the solid crust of the world.

Owing to the intense heat, chemical combinations would readily be formed between the ingredients of the fused mass and the other elements which existed in the form of vapour, and thus the earliest of the vast variety of existing minerals would be elaborated.  The volumes of steam which floated in the upper regions of the atmosphere would rapidly part with their heat by radiation into space, and would descend towards the surface of the earth in the form of rain.  At first probably, and for a long time, they would