Hurriedly he removed the plate from the pillow and replaced the phial of liquid. There was only a very feeble glow.
"Good enough," he cried. "Take away the glass, but mark that pane, and be ready to replace it when I give the word."
From the instrument case he had brought he took out a spectroscope. He turned back the mattress and mounted it on the bedstead.
"Cover that pane," he directed.
Carnes did so, and the Doctor swung the receiving tube of the instrument until it pointed at the covered pane. He glanced into the eyepiece, and then held a tiny flashlight for an instant opposite the third tube.
"Uncover that pane," he said.
Carnes took down the glass plate and the Doctor gazed into the instrument. He made some adjustments.
"Are you familiar with spectroscopy, Admiral?" he asked.
"Somewhat."
"Take a squint in here and tell me what you see."