 Who was talking to Jerome in the very beginning of the passage?
There is one fact no sane man can quarrel with ... You will, you know, so why quibble about it? Yes, it'll be pretty obvious it must be a time machine. You'll be puzzling over what I'll tell you, and you'll be getting used to the idea that you are the man who makes atomic power practical. You won't exactly believe it, but you'll want to go along. You are completely outside of time and space, as best you can guess how things are. Then it comes to you slowly that you're actually traveling in time. Well, I asked it after I was told, then I came back and told it to you, and I still can't help answering when you speak. "Maybe it's no dimension—or it might be the fifth; if you're going to skip over the so-called fourth without traveling along it, you'd need a fifth. I figured out once that such a universe would need some seven or eight time and space dimensions. When you spend thirty years thinking about it, as I did—and you will—you get further and further from an answer. That means you either carry a small time field with you, or you are catching a small increment of time from the main field. Out there is neither time nor space, apparently. In spite of Einstein, you have always had the idea that time is an effect of gravity, and I sort of agree, still. He told me, just as I'm telling you, that it's an interstellar civilization." We have to walk up a flight of stairs, and there is an elevator waiting, fortunately with the door open. It gives out a coughing noise and the basement openings begin to click by us. There's no feeling of acceleration—some kind of false gravity they use in the future. A second later, you see me going by, mixed into a crowd that is loafing along toward a restaurant, or something like it, that is just opening. I'm asking questions of a man, who points, and I turn and move off. Some of them can be decoded to stationery shops, fountains, and the like. But there is only a single picture of a dull-looking metal sphere, with passengers moving up a ramp, and the office is closed. Around you, you hear some pretty normal English, but there are others using stuff as garbled as his.
 Jerome, from 30 years in the future
 Jerome, from 30 years in the past  Jerome, from 10 years in the past  Jerome, from 10 years in the future  Jerome, from 30 years in the future