They were now hovering beside a massive - yet still surprisingly small - cylinder that might have been the barrel of a twentieth-century naval gun. So this was the reaction chamber of the Drive...

Near the middle of the five-meter-long tube a small section of the casing had been removed, like the door of some miniature bank vault, and replaced by a crystal window... a microscope... was aimed into the interior of the drive unit.

Duncan floated to the eyepiece and fastened himself rather clumsily in place.

"Look at the crossover at the exact center," said his guide.

Duncan obeyed... then he realized that a tiny bulge was creeping along the hairline as he tracked the microscope. It was as if he was looking at the reticule through a sheet of glass with one minute bubble or imperfection in it.

[It's] like a pinhead-sized lens. Without the grid, you'd never see it."

"Pinhead-sized! That's an exaggeration if ever I heard one. The node's smaller than an atomic nucleus. You're not actually seeing it, of course - only the distortion it produces."

"And yet there are thousands of tons of matter in there."