On the end of the yacht club dock Kennedy and Armand set up a large affair which looked like a mortar. I watched curiously, dividing my attention between them and the splendid view of the harbor which the end of the dock commanded on all sides.

“What is this?” I asked finally. “Fireworks?”

“A rocket mortar of light weight,” explained Kennedy, then dropped into French as he explained to Armand the manipulation of the thing.

There was a searchlight near by on the dock.

“You can use that?” queried Kennedy.

“Oh, yes. Mr. Verplanck, he is vice-commodore of the club. Oh, yes, I can use that. Why, Monsieur?”

Kennedy had uncovered a round brass case. It did not seem to amount to much, as compared to some of the complicated apparatus he had used. In it was a four-sided prism of glass—I should have said, cut off the corner of a huge glass cube.

He handed it to us.

“Look in it,” he said.

It certainly was about the most curious piece of crystal gazing I had ever done. Turn the thing any way I pleased and I could see my face in it, just as in an ordinary mirror.