"Fuse blew," said Barney shortly. He gumbled his way through the dark house and replaced the fuse. He returned smiling. "Fixed that one," he told Jim. "Put a washer behind it." "O.K. Hit the switch again." Barney cranked the power over, and once more the meters climbed up across the scales. There was a groaning sound from the tube, and the smell of burning insulation filled the room. One meter blew with an audible sound as the needle hit the end stop, and immediately afterward the lights in the entire block went out. "Fix that one by hanging a penny behind it," said Jim with a grin. "That's a job for Martian Electric to do," laughed Barney. Several blocks from there, an attendant in the substation found the open circuit-breaker and shoved it in with a grim smile. He looked up at the power-demand meter and grunted. High for this district, but not dangerous. Duration, approximately fifteen seconds. Intensity, higher than usual but not high enough to diagnose any failure of the wiring in the district. "Ah, well," he thought, "we can crank up the blow-point on this breaker if it happens again." He turned to leave and the crashing of the breaker scared him out of a week's growth. He snarled and said a few choice words not fit for publication. He closed the breaker and screwed the blow-point control up by two-to-one. "That'll hold 'em," he thought, and then the ringing of the telephone called him to his office, and he knew that he was in for an explanatory session with some people who wanted to know why their lights were going on and off. He composed a plausible tale on his way to the phone. Meanwhile, he wondered about the unreasonable demand and concluded that one of the folks had just purchased a new power saw or something for their home workshop. "Crack the juice about a half," suggested Barney. "That'll keep us on the air until we find out what kind of stuff this thing takes. The book claims about one tenth of the current-drain for this unit. Something we've missed, no doubt." "Let's see that circuit," said Jim. After a minute, he said: "Look, guy, what are these screws for?" "They change the side plate voltages from about three hundred to about three hundred and fifty. I've got 'em set in the middle of the range." "Turn us on half voltage and diddle one of 'em." "That much of a change shouldn't make the difference," objected Barney. "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."