As she waited there in the silence and the dark, Valeska strained her eyes for nearly a minute in vain. Then a faint luminous blur was apparent. It gathered intensity and showed a triangle of violet radiance. In another minute it had taken the form of a squatting Buddha and glowed plainly, the only visible thing in the room.
"It's wonderful!" she breathed.
"Oh, that's not half that can be done with black light," Astro said, as he took the lantern and led the way out. "With it one can photograph objects through an opaque screen, when they are illuminated by ordinary sunlight. By using a screen of sulfid of zinc, and training this black light upon an object, one could see it even at midnight, half a mile away."
When they came out into the great studio, he dropped to his favorite place on the divan and went on. "Phosphorescence, opalescence and fluorescence are queer things, Valeska. They haven't been half understood till lately, when what is called 'the new physics' came into being through the discoveries in radioactivity by Monsieur and Madame Curie. It used to be thought that after a phosphorescent object had remained in the dark for a while and had ceased to be luminous, it ceased its radioactivity, and needed a new bath of light to make it act again. But Le Bon found that it would radiate for months after all visible glow had disappeared. We have proved it with this black light just now."
He had taken up his narghile and sat looking off into space with a mystic expression on his face. It was one of his dreamy, philosophical moments. Valeska recognized the mood and waited for the inevita-
