I have taken certain liberties with several more or less commonly accepted theories, but I assure you that those theories have not been violated altogether in ignorance. Some of them I myself believe sound, others I consider unsound, still others are out of my line, so that I am not well enough informed upon their basic mathematical foundations to have come to any definite conclusion, one way or the other. Whether or not I consider any theory sound, I did not hesitate to disregard it, if its literal application would have interfered with the logical development of the story. In "The Skylark of Space" Mrs. Garby and I decided, after some discussion, to allow two mathematical impossibilities to stand. One of these immediately became the target of critics from Maine to California and, while no astronomer has as yet called attention to the other, I would not be surprised to hear about it, even at this late date. While I do not wish it understood that I regard any of the major features of this story as likely to become facts in the near future--indeed, it has been my aim to portray the highly improbable--it is my belief that there is no mathematical or scientific impossibility to be found in "Skylark Three." In fact, even though I have repeatedly violated theories in which I myself believe, I have in every case taken great pains to make certain that the most rigid mathematical analysis of which I am capable has failed to show that I have violated any known and proven scientific fact. By "fact" I do not mean the kind of reasoning, based upon assumptions later shown to be fallacious, by which it was "proved" that the transatlantic cable and the airplane were scientifically impossible. I refer to definitely known phenomena which no possible future development can change--I refer to mathematical proofs whose fundamental equations and operations involve no assumptions and contain no second-degree uncertainties. Please bear in mind that we KNOW very little. It has been widely believed that the velocity of light is the limiting velocity, and many of our leading authorities hold this view--but it cannot be proved, and is by no means universally held. In this connection, it would appear that J. J. Thompson, in "Beyond the Electron" shows, to his own satisfaction at least, that velocities vastly greater than that of light are not only possible, but necessary to any comprehensive investigation into the nature of the electron.