Doc explained the operation of the time machine to me.

'It's simple,' he said. 'Simple as falling off a log.'

And what he said was true. All you had to do was set the indicator forward the number of years you wished to travel. When you pressed the activator stud you went into the time spin, or whatever it was that happened to you, and you stayed in it until you reached the proper time. Then the mechanism acted automatically, your time speed was slowed down, and there you were. You just reversed the process to go backward.

Simple. Simple, so Doc said, as falling off a log. But I knew that behind all that simplicity was some of the most wonderful science the world had ever known – science and brains and long years of grueling work and terrible disappointment.

'It will be like plunging into night.' Doc told me. 'You will be traveling in time as a single dimension. There will be no heat, no air, no gravitation, absolutely nothing outside your plane. But the plane is insulated to keep in the heat. In case you do get cold, just snap on those heaters. Air will be supplied if you need it, by the oxygen tanks. But on a short trip like five hundred years you probably won't need either the heaters or the oxygen. Just a few minutes and you'll be there.'

J.R. had been sore at me because I had been late. Sore, too, because Herb had one of the most beautiful hangovers I have ever laid eyes on. But he'd forgotten all about that now. He was hopping up and down in his excitement.

'Just wait,' he chortled. 'Just wait until Johnson sees this down at the Standard . He'll probably have a stroke. Serve him right, the stubborn old buzzard.'

The guard, standing just outside the door of the ship, was shuffling his feet. For some reason the fellow seemed nervous.

Doc croaked at him. 'What's the matter with you, Benson?'