"That plate seems to glow," he said in an astonished voice.
Dr. Bird stepped forward and laid his hand on the pillow. He was wearing a wrist watch with a radiolite dial. The substance suddenly increased its luminescence and began to glow fiercely, long luminous streamers seeming to come from the dial. The Doctor took away his hand and substituted a bottle of liquid for the plate on the pillow. Immediately the bottle began to glow with a phosphorescent light.
"What on earth is it?" gasped Carnes.
"Excitation of a radioactive fluid," replied the Doctor. "The question is, what is exciting it. Somebody get a stepladder."
While Bolton was gone after the ladder, the Doctor took from his bag what looked like an ordinary pane of glass.
"Take this, Carnes," he directed, "and start holding it over each of those panes of quartz which you can reach. Stop when I tell you to."
The operative held the glass over each of the panes in succession, but the Doctor, who kept his eyes covered with the smoked glasses and fastened on the plate which he had replaced on the pillow, said nothing. When Bolton arrived with the ladder, the process went on. One end and most of the front of the solarium had been covered before an exclamation from the Doctor halted the work.
"That's the one," he exclaimed. "Hold the glass there for a moment."