“I regret to say it is,” Sorrel replied; “it would be just as hopeless for you, in your life-time, to hunt up, classify, and elucidate the life-history of every fly and grub and bacillus on this planet, from the very beginning.” “Just so, Sorrel, but tell us what you think; how it _may_ have come here. Has the sun blown out and the internal nitrogen and what not developed this kernel more rapidly?” “I don’t like stating mere theories, Spenser,” answered Sorrel, smiling, “but as you press me I will tell you what I imagine has been the case. The only thing I can conceive as being in any way possible is that the sun may have been formed by an extremely large planet attracting to its mass another large planet of less gravity, the impact forming this present sun. If a portion of one of the worlds, however, embedded itself in the centre by probably an earthquake at the moment of impact, there would be no immediate contact, and consequently no immediate fusion of this portion, but directly the contact came, perhaps less than a second later, there would be instant cohesion, and also instant expansion of the parts brought into contact, which would allow the embedding portion to touch nothing; it would strike to the centre and remain there, because it would then have reached equally opposing forces all round, and would commence to float and revolve in space enveloped by the atmosphere projected with it, and probably some instant conversion of some of the nitrates, or metallic portions of the immense globule, would create a crust and generate a deep layer of nitrogen, which would prevent further combustion downwards; the ordinary breathable air below would remain there, with only a slight intermingling in the extreme upper strata, which are further held in place and away from the atmosphere here by that wonderful zone of thick clouds which so deceived us, they forming natural shields, or vanes. In any case, the cold centre would cause the outer crust to move away from it, and expand, and conduce to the cooling of the crust, as would also the nitrogen, being a non-supporter of combustion; the world itself would become comparatively round and revolve as our Earth does, in its own atmosphere. Then the usual cycle of waste and repair would follow, and the air be made and kept sweet and fresh; the animal kingdom would give out carbonic-acid gas and inhale oxygen, whilst the vegetable kingdom would inhale carbonic acid and exhale oxygen, thus each kingdom giving out as a waste product that which was necessary to the existence of the other, as on Earth, the general health and safety of both kingdoms being thus maintained, for each is indispensable to the other. “This is my explanation, and though it may seem to you at first thought somewhat fanciful, I believe it is the one and only correct solution, and it is at least a scientific possibility that will bear argument.”