... For obvious reasons, those who possessed the secret of the Apergy [1] had never dreamed of applying it in the manner I proposed. It had seemed to them little more than a curious secret of nature, perhaps hardly so much, since the existence of a repulsive force in the atomic sphere had been long suspected and of late certainly ascertained, and its preponderance is held to be the characteristic of the gaseous as distinguished from the liquid or solid state of matter. Till lately, no means of generating or collecting this force in large quantity had been found. The progress of electrical science had solved this difficulty; and when the secret was communicated to me, it possessed a value which had never before belonged to it. Ever since, in childhood, I learnt that the planets were worlds, a visit to one or more of the nearest of them had been my favourite day-dream. Treasuring every hint afforded by science or fancy that bore upon the subject, I felt confident that such a voyage would be one day achieved. Helped by one or two really ingenious romances on this theme, I had dreamed out my dream, realised every difficulty, ascertained every factor in the problem. I had satisfied myself that only one thing needful was as yet wholly beyond the reach and even the proximate hopes of science. Human invention could furnish as yet no motive power that could fulfil the main requirement of the problem—uniform or constantly increasing motion _in vacuo_—motion through a region affording no resisting medium. This must be a _repulsive_ energy capable of acting through an utter void. Man, animals, birds, fishes move by repulsion applied at every moment. In air or water, paddles, oars, sails, fins, wings act by repulsion exerted on the fluid element in which they work. But in space there is no such resisting element on which repulsion can operate. I needed a repulsion which would act like gravitation through an indefinite distance and in a void—act upon a remote fulcrum, such as might be the Earth in a voyage to the Moon, or the Sun in a more distant journey. As soon, then, as the character of the apergic force was made known to me, its application to this purpose seized on my mind. Experiment had proved it possible, by the method described at the commencement of this record, to generate and collect it in amounts practically unlimited. The other hindrances to a voyage through space were trivial in comparison with that thus overcome; there were difficulties to be surmounted, not absent or deficient powers in nature to be discovered. The chief of these, of course, concerned the conveyance of air sufficient for the needs of the traveller during the period of his journey. The construction of an air-tight vessel was easy enough; but however large the body of air conveyed, even though its oxygen should not be exhausted, the carbonic acid given out by breathing would very soon so contaminate the whole that life would be impossible.