Mark considered for a moment. Then:
"The impression I get is that this mirror was poured into a circular form, instead of being cut to shape. And that while it was still molten, something struck it in the center, so that little ripples formed in the glass, all the way from the center to the outer edge."
It was the scientist's turn to nod.
"Precisely my own view."
Moving away, he selected a candlestick and candle from among the gifts on display. He handed it to Mark.
"I want you to move this stick in front of that glass," he instructed. "However, you must be careful to stand well to one side, so that you, yourself, will not be reflected."
"What's the angle, professor? What do you expect to find? What's wrong with this mirror?"
The elder man shook his head, moved to a point where he could watch the surface of the glass.
"I do not know what to expect," he said. "I may be completely on the wrong track."