The Glamorgan bored on through space. Not normal space, of course. In the ordinary sort of space between suns and planets and solar systems generally, a ship is strictly limited to ninety-eight-point-something per cent of the speed of light, because mass increases with speed, and inertia increases with mass. But in an overdrive field the properties of space are modified. The effect of a magnet on iron is changed past recognition. The effect of electrostatic stress upon dielectrics is wholly abnormal. And inertia, instead of multiplying itself with high velocity, becomes as undetectable as at zero velocity. In fact, theory says that a ship has no velocity on an overdrive field. The speed is of the field itself. The ship is carried. It goes along for the ride.

But there was no thinking about such abstractions on the Glamorgan. The effect of overdrive was the same as if the ship did pierce space at many times the speed of light. Obviously, light from ahead was transposed a great many octaves upward, into something as different from light as long wave radiation is from heat. This radiation was refracted outward from the ship by the overdrive field, and was therefore without effect upon instruments or persons. Light from behind was left there. Light from the sides was also refracted outward and away. The Glamorgan floated at ease in a hurtling, unsubstantial space-stress center, and to try to understand it might produce a headache, but hardly anything more useful.

But though the Glamorgan in overdrive attained the end of speed without the need for velocity, the human relationship between Link and Thistlethwaite was less simple. The whiskery little man was impassioned about his enterprise. Link had guessed his highly secret destination, and Thistlethwaite was outraged by the achievement.