Then he did what seemed a foolish thing. He took the globe of red fruit from his pocket and sliced it neatly into thin layers. Don laid the dripping slices atop the copper plate, and then, his heart cold as ice, laid the zinc plate atop the fruit.
The Martians watched coldly, grunting to themselves. Their eyes were on the world-old motor. Slowly, incredibly, the thing turned over. The straps sped over the drums; the brushes fizzed and emitted inch-long blue sparks.
And from overhead came a sudden, terrifying wail like nothing that had been heard on Mars for countless ages. It was not the cry of an animal nor of a man—that was all the boy knew as he backed against a wall of the building. The noise rose sickeningly in a demoniacal shriek. The Martians seemed paralyzed by the awful sound. Then, with choking cries, they broke ground and ran, their eyes popping and the shout, "Kursah-ekh!" bursting from their lips. Don knew little of the language, but he did know that their cry was "Demons!"
The natives fled with the speed of wild things, and the boy found himself alone. No, not quite alone, for into the door of the little building poked the familiar old head of Gecko, Don's pack-lizard. He nearly embraced the ugly creature. It would have been hell to go without water for another minute. From the canteen on the Iguana's back Don took a long, refreshing swig. Then he turned again to the motor.
It was still turning over, but more slowly. He was about to separate the plates when it stopped of its own accord and the fiendish wail from above died away. The boy nimbly scaled the web-work construction and pried about the tangle of machinery until he found the obvious answer. It had been a blower operated by the motor, to which had been attached a simple siren. Burglar-alarm, perhaps, or danger signal, he thought. At any rate it had saved him.
He laughed as he descended slowly. The old book had been right. Fruit acid between zinc and copper made the simplest sort of generating battery cell. What knowledge he had possessed he had used to the full. He drank again from the canteen.
And a few moments later with Gecko at his side, he left the city of the dead behind, Don was going to a greener world.