A World is Born, Leigh Brackett, Comet, July 1941. Note: The copyright for this story has expired in the United States and, thus, now resides in the public domain. 

The electric beasts had finished their pleasure. The dead were cinders on the rock. The living had run back into the tunnels. And now the blue sea of fire was flowing again, straight toward the place where they stood.
It was flowing fast, and Gray sensed an urgency, an impersonal haste, as though a command had been laid upon those living ropes of flame.
The first dim rumble of thunder rolled down the wind. Gripping Jill, Gray turned up the tunnel.
The wind, compressed in that narrow throat of rock, beat them blind and breathless, beat them to their bellies, to crawl. How long it took them, they never knew.
But Gray caught glimpses of Dio the Martian crawling behind them, and behind him again, the relentless flow of the fire-things.
They floundered out onto a rocky slope, fell away beneath the suck of the wind, and lay still, gasping. It was hot. Thunder crashed abruptly, and lightning flared between the cliffs.
Gray felt a contracting of the heart. There were no cables.
Then he saw it--the small, fast fighter flying below them on a flat plateau. A cave mouth beside it had been closed with a plastic door. The ship was the one that had followed them. He guessed at another one behind the protecting door.
Raking the tumbled blond hair out of his eyes, Gray got up.
Jill was still sitting, her black curls bowed between her hands. There wasn't much time, but Gray yielded to impulse. Pulling her head back by the silken hair, he kissed her.
"If you ever get tired of virtue, sweetheart, look me up." But somehow he wasn't grinning, and he ran down the slope.
He was almost to the open lock of the ship when things began to happen. Dio staggered out of the wind-tunnel and sagged down beside Jill. Then, abruptly, the big door opened.
Five men came out--one in pilot's costume, two in nondescript apparel, one in expensive business clothes, and the fifth in dark prison garb.
Gray recognized the last two. Caron of Mars and the errant Ward.
They were evidently on the verge of leaving. But they looked cheerful. Caron's sickly-sweet face all but oozed honey, and Ward was grinning his rat's grin.
Thunder banged and rolled among the rocks. Lightning flared in the cloudy murk. Gray saw the hull of a second ship beyond the door. Then the newcomers had seen him, and the two on the slope.
Guns ripped out of holsters. Gray's heart began to pound slowly. He, and Jill and Dio, were caught on that naked slope, with the flood of electric death at their backs.
His Indianesque face hardened. Bullets whined round him as he turned back up the slope, but he ran doubled over, putting all his hope in the tricky, uncertain light.
Jill and the Martian crouched stiffly, not knowing where to turn. A flare of lightning showed Gray the first of the firethings, flowing out onto the ledge, hidden from the men below.
"Back into the cave!" he yelled. His urgent hand fairly lifted Dio. The Martian glared at him, then obeyed. Bullets snarled against the rock. The light was too bad for accurate shooting, but luck couldn't stay with them forever.
Gray glanced over his shoulder as they scrambled up on the ledge. Caron waited by his ship. Ward and the others were charging the slope. Gray's teeth gleamed in a cruel grin.
Sweeping Jill into his arms, he stepped into the lapping flow of fire. Dio swore viciously, but he followed. They started toward the cave mouth, staggering in the rush of the wind.
"For God's sake, don't fall," snapped Gray. "Here they come!"
The pilot and one of the nondescript men were the first over. They were into the river of fire before they knew, it, and then it was too late. One collapsed and was buried. The pilot fell backward, and then other man died under his body, of a broken neck.
Ward stopped. Gray could see his face, dark and hard and calculating. He studied Gray and Dio, and the dead men. He turned and looked back at Caron. Then, deliberately, he stripped off his gun belt, threw down his gun, and waded into the river.
Gray remembered, then, that Ward too wore rubber boots, and had no metal on him.
-- -- -- -- -- -- -- -- -- --
Ward came on, the glowing ropes sliding surf-like around his boots. Very carefully. Gray handed Jill to Dio.
"If I die too," he said, "there's only Caron down there. He's too fat to stop you."
Jill spoke, but he turned his back. He was suddenly confused, and it was almost pleasant to be able to lose his confusion in fighting. Ward had stopped some five feet away. Now he untied the length of tough cord that served him for a belt.
Gray nodded. Ward would try to throw a twist around his ankle and trip him. Once his body touched those swarming creatures....
He tensed, watchfully. The rat's grin was set on Ward's dark face. The cord licked out.
But it caught Gray's throat instead of his ankle!
Ward laughed and braced himself. Cursing, Gray caught at the rope. But friction held it, and Ward pulled, hard. His face purpling, Gray could still commend Ward's strategy. In taking Gray off guard, he'd more than made up what he lost in point of leverage.
Letting his body go with the pull, Gray flung himself at Ward. Blood blinded him, his heart was pounding, but he thought he foresaw Ward's next move. He let himself be pulled almost within striking distance.
Then, as Ward stepped, aside, jerking the rope and thrusting out a tripping foot, Gray made a catlike shift of balance and bent over.
His hands almost touched that weird, flowing surf as they clasped Ward's boot. Throwing all his strength into the lift, he hurled Ward backward.
Ward screamed once and disappeared under the blue fire. Gray clawed the rope from his neck. And then, suddenly, the world began to sway under him. He knew he was falling.
Some one's hand caught him, held him up. Fighting down his vertigo as his breath came back, he saw that it was Jill.
"Why?" he gasped, but her answer was lost in a titanic roar of thunder. Lightning blasted down. Dio's voice reached him, thin and distant through the clamor.
"We'll be killed! These damn things will attract the bolts!"
It was true. All his work had been for nothing. Looking up into that low, angry sky, Gray knew he was going to die.
Quite irrelevantly, Jill's words in the tunnel came back to him. "You're a fool ... lost truth ... not true to lie!"
Now, in this moment, she couldn't lie to him. He caught her shoulders cruelly, trying to read her eyes.
Very faintly through the uproar, he heard her. "I'm sorry for you, Gray. Good man, gone to waste."
Dio stifled a scream. Thunder crashed between the sounding boards of the cliffs. Gray looked up.
A titanic bolt of lightning shot down, straight for them. The burning blue surf was agitated, sending up pseudopods uncannily like worshipping arms. The bolt struck.
The air reeked of ozone, but Gray felt no shock. There was a hiss, a vast stirring of creatures around him. The blue light glowed, purpled.
Another bolt struck down, and another, and still they were not dead. The fire-things had become a writhing, joyous tangle of tenuous bodies, glowing bright and brighter.
Stunned, incredulous, the three humans stood. The light was now an eye-searing violet. Static electricity tingled through them in eerie waves. But they were not burned.
"My God," whispered Gray. "They eat it. They eat lightning!"
Not daring to move, they stood watching that miracle of alien life, the feeding of living things on raw current. And when the last bolt had struck, the tide turned and rolled back down the wind-tunnel, a blinding river of living light.
Silently, the three humans went down the rocky slope to where Caron of Mars cowered in the silver ship. No bolt had come near it. And now Caron came to meet them.
His face was pasty with fear, but the old cunning still lurked in his eyes.
"Gray," he said. "I have an offer to make."
"You killed my pilot," said Caron suavely. "I can't fly, myself. Take me off, and I'll pay you anything you want."
"In bullets," retorted Gray. "You won't want witnesses to this."
"Circumstances force me. Physically, you have the advantage."
Jill's fingers caught his arm. "Don't, Gray! The Project...."
Caron faced her. "The Project is doomed in any case. My men carried out my secondary instructions. All the cables in your valley have been cut. There is a storm now ready to break.
"In fifteen minutes or so, everything will be destroyed, except the domes. Regrettable, but...." He shrugged.
Jill's temper blazed, choking her so that she could hardly speak.
"Look at him, Gray," she whispered. "That's what you're so proud of being. A cynic, who believes in nothing but himself. Look at him!"
Gray turned on her.
"Damn you!" he grated. "Do you expect me to believe you, with the world full of hypocrites like him?"
Her eyes stopped him. He remembered Moulton, pleading for her life. He remembered how she had looked back there at the tunnel, when they had been sure of death. Some of his assurance was shaken.
"Listen," he said harshly. "I can save your valley. There's a chance in a million of coming out alive. Will you die for what you believe in?"
She hesitated, just for a second. Then she looked at Dio and said, "Yes."
Gray turned. Almost lazily, his fist snapped up and took Caron on his flabby jaw.
"Take care of him, Dio," he grunted. Then he entered the ship, herding the white-faced girl before him.
-- -- -- -- -- -- -- -- -- --
The ship hurtled up into airless space, where the blinding sunlight lay in sharp shadows on the rock. Over the ridge and down again, with the Project hidden under a surf of storm-clouds.
Cutting in the air motors, Gray dropped. Black, bellowing darkness swallowed them. Then he saw the valley, with the copper cables fallen, and the wheat already on fire in several places.
Flying with every bit of his skill, he sought the narrowest part of the valley and flipped over in a racking loop. The stern tubes hit rock. The nose slammed down on the opposite wall, wedging the ship by sheer weight.
Lightning gathered in a vast javelin and flamed down upon them. Jill flinched and caught her breath. The flame hissed along the hull and vanished into seared and blackened rock.
"Still willing to die for principle?" asked Gray brutally.
She glared at him. "Yes," she snapped. "But I hate having to die in your company!"
She looked down at the valley. Lightning struck with monotonous regularity on the hull, but the valley was untouched. Jill smiled, though her face was white, her body rigid with waiting.
It was the smile that did it. Gray looked at her, her tousled black curls, the lithe young curves of throat and breast. He leaned back in his seat, scowling out at the storm.
"Relax," he said. "You aren't going to die."
She turned on him, not daring to speak. He went on, slowly.
"The only chance you took was in the landing. We're acting as lightning rod for the whole valley, being the highest and best conductor. But, as a man named Faraday proved, the charge resides on the surface of the conductor. We're perfectly safe."
"How dared you!" she whispered.
He faced her, almost angrily.
"You knocked the props out from under my philosophy. I've had enough hypocritical eyewash. I had to prove you. Well, I have."
She was quiet for some time. Then she said, "I understand, Duke. I'm glad. And now what, for you?"
He shrugged wryly.
"I don't know. I can still take Caron's other ship and escape. But I don't think I want to. I think perhaps I'll stick around and give virtue another whirl."
Smoothing back his sleek fair hair, he shot her a sparkling look from under his hands.
"I won't," he added softly, "even mind going to Sunday School, if you were the teacher."