"And I alone have hit upon the right plan, because I have not attempted to _struggle against_ gravity, but have made use of it only for propelling my projectile!" exclaimed the doctor triumphantly. "But wait!" I interposed. "Gravity acts only in one direction, and that is exactly opposite to the one you propose to travel." "That brings me to the very important discovery I made in physics two years ago, upon which the whole success of the projectile rests. You will remember that, according to the text-books, very little is known about gravity except the laws of its action. What it is, and how it can be controlled or modified, have never been known. Electricity was as much a mystery fifty years ago, but we know all its attributes. We can make it, store it, control it, and use it for almost every necessity of life. The era of electricity is in full bloom, but the era of gravitational force is just budding." "Can it be that we have as much to learn from gravity as electricity has taught us in the last half-century?" I exclaimed, as my eyes began to open. "I believe it will teach us far more wonderful things, because it will take us to unknown worlds, while electricity has been confined to Earth. Its realm is the wide universe. It will show us what life there is on the planets. It will make us at home with the stars. "What!" he continued in a sort of ecstasy. "Do you think all great discoveries are over, all wonderful inventions made? As well might a trembling child, elated with the success of its first feeble steps alone, suppose it had exhausted all the possibilities of life. We are but spelling over the big letters on the title page of the primary book of knowledge. There be other pages and grander chapters further on. There be greater volumes, and sweeter, more expressive tongues which man may learn some day. "Has a reasoning Divinity created the heavens and peopled the myriad stars with thinking, capable beings, who must be perpetually isolated? Or may they not know each other some time? But shall we attempt to sail the vast heavens with a paper kite, or try to fly God's distances with the wings of fluttering birds? Nay; we must use God's engine for such a task. Has He tied the planets to the sun, and knitted the suns and their systems into one great universe obedient to a single law, with no possibility that we may use that law for intercommunication? With what wings do the planets fly around the sun, and the suns move through the heavens? With the wings of gravity! The same force for minute satellite or mighty sun. It is God's omnipotence applied to matter. Let us fly with that!" "But will you permit me to suggest that we are soaring before the projectile is built?" I put in.