"Brother, we don't know what this thing is even for," reminded Jim. "Much less do we know the effect of anything on it. Diddle, I say."
"O.K., we diddle." Barney turned on half power and reached into the maze of wiring and began to tinker with one of the screws. "Hm-m-m," he said after a minute. "Does things, all right. She goes through some kind of resonance point or something. There is a spot of minimum current here. There! I've hit it. Now for the other one."
For an hour, Barney tinkered with first one screw and then the other one. He found a point where the minimum current was really low; the two screws were interdependent and only by adjusting them alternately was he able to reach the proper point on each. Then he smiled and thrust the power on full. The current remained at a sane value.
"Now what?" asked Barney.
"I don't know. Anything coming out of the business end?"
"Heat."
"Yeah, and it's about as lethal as a sun lamp. D'ye suppose the Martians used to artificially assist their crops by synthetic sunshine?"
Barney applied his eye to a spectroscope. It was one of the newer designs that encompassed everything from short ultraviolet to long infrared by means of fluorescent screens at the invisible wave lengths. He turned the instrument across the spectrum and shook his head. "Might be good for a chest cold," he said, "but you wouldn't get a sunburn off of it. It's all in the infra. Drops off like a cliff just below the deep red. Nothing at all in the visible or above. Gee," he said with a queer smile, "you don't suppose that they died off because of a pernicious epidemic of colds and they tried chest-cooking en masse?"
