Out on the rolling skyline, fifty miles away, a lancelike ray of blue-white light shot up into the gathering dusk—a clump of five rays, really, from five deep shafts in an irregular pentagon half a mile across, blended into one by the distance. An instant later, there was a blinding flash, like sheet-lightning, and a huge ball of varicolored fire belched upward, leaving a series of smoke-rings to float more slowly after it. The fireball flattened, then spread to form the mushroom-head of a column of incandescent gas that mounted to overtake it, engorging the smoke-rings as it rose, twisting, writhing, changing shape, turning to dark smoke in one moment and belching flame and crackling with lightning the next.
"In about half an hour," the large young man told Paula Quinton, "the real fireworks should be starting. What's coming up now is just small debris from the nuclear blast. When the shock-waves get down far enough to crack things open, the gas'll come up, and then steam and ash, and then magma."
"Well, even this was worth staying over for," the girl said, watching the screen.
"You going on to Ullr on the City of Canberra?" Lourenço Gomes asked. "I wish I were; I have to stay over and make another shot, in a month or so, and I've had about all of Niflheim I can take, now."
"When are you going to Terra?" the girl asked him.
"Terra? I don't know; a year, two years. But I'm going to Ullr on the next ship—the City of Pretoria—if we get the next blast off in time. They want me to design some improvements on a couple of power-reactors at Keegark so I'll probably see you when I get there."
"Here she comes!" the chief engineer called. "Watch the base of the column!"
The pillar of fiery smoke and dust, still boiling up from where the bombs had gone off far underground, was being violently agitated at the bottom. A series of new flashes broke out, lifting and spreading the incandescent radioactive gasses, and then a great gush of flame rose. A column of pure hydrogen must have rushed up into the vacuum created by the explosion; the next blast of flame, in a lateral sheet, came at nearly ten thousand feet above the ground. Then geysers of hot ash and molten rock spouted upward; some of the white-hot debris landed almost at the acid river, half-way to the armor-tender.
"We've started a first-class earthquake, too," Murillo said, looking at the instruments.