"I mean," he replied, "that I was born in the year 2028. I am forty-three years old--or I was a few minutes ago. But,"--and his eyes flickered again with that strange, mad light--"I am a scientist! I have left my age behind me for a time; I have done what no other human being has ever done: I have gone centuries into the future!" "I--I do not understand." Could he, after all, be a madman? "How can a man leave his own age and travel ahead to another?" "Even in this age of yours they have not discovered that secret?" Harbauer exulted. "You travel the Universe, I gather, and yet your scientists have not yet learned to move in time? Listen! Let me explain to you how simple the theory is. * * * * * "I take it you are an intelligent man; your uniform and its insignia would seem to indicate a degree of rank. Am I correct?" "I am John Hanson, Commander of the _Ertak_, of the Special Patrol Service," I informed him. "Then you will be capable of grasping, in part at least, what I have to tell you. It is really not so complex. Time is a river, flowing steadily, powerful, at a fixed rate of speed. It sweeps the whole Universe along on its bosom at that same speed. That is my conception of it; is it clear to you?" "I should think," I replied, "that the Universe is more like a great rock in the middle of your stream of time, that stands motionless while the minutes, the hours, and the days roll by." "No! The Universe travels on the breast of the current of time. It leaves yesterday behind, and sweeps on towards to-morrow. It has always been so until I challenged this so-called immutable law. I said to myself, why should a man be a helpless stick upon the stream of time? Why need he be borne on this slow current at the same speed? Why cannot he do as a man in a boat, paddle backwards or forwards; back to a point already passed; ahead, faster than the current, to a point that, drifting, he would not reach so soon? In other words, why can he not slip back through time to yesterday; or ahead to to-morrow? And if to to-morrow, why not to next year, next century? * * * * * "These are the questions I asked myself. Other men have asked themselves the same questions, I know; they were not new. But,"--Harbauer drew himself far forward in his chair, and leaned close to me, almost as though he prepared himself to spring--"no other man ever found the answer! That remained for me. "I was not entirely correct, of course. I found that one could not go back in time. The current was against one. But to go ahead, with the current at one's back, was different. I spent six years on the problem, working day and night, handicapped by lack of funds, ridiculed by the press--Look!" Harbauer reached inside his antiquated costume and drew forth a flat packet which he passed to me. I unfolded it curiously, my fingers clumsy with excitement.