Eek!”
Grag, lumbering forward like a ponderous metal engine, made no reply to the taunt. The Moon Dogs were closing on them by leaps and bound. The fissure was still a hundred yards ahead. Curt felt desperately that they could never reach it in time. Then Simon made a diversion.
The Brain flew back right into the face of the charging Moon Dogs, jetting his shining tractor beams into their faces. The creatures recoiled in momentary terror. It gave Curt and the other two Futuremen time to reach the fissure. They tumbled into it, Simon flashing after them.
The Moon Dogs reached the mouth of the narrow fissure an instant later. The ravenous beasts jammed in the entrance, in their avid eagerness to get at the Futuremen. But Grag now stood in their way, and with his heavy metal bar the great robot belabored the gray brutes.
The Moon Dogs retreated hastily from the robot’s blows. Again they charged, but again they could not enter the narrow crevasse past him. Balked, the creatures crouched down outside the fissure to wait.
“Now what do we do?” Otho asked anxiously. “If we start down the fissure, they’ll be right after us.”
Curt gestured to the loose masses of shattered rock that almost choked the passage.
“We can build up a wall that will hold them out.”
They labored at that for almost an hour, carrying heavy masses of rock and placing them until they had a wall of eight feet high across the crevasse. The Moon Dogs could never pass it.
The Futuremen stopped then for breath. Wonderingly, Otho looked down the fissure. It was a narrow split in the rock, angling steeply downward into impenetrable darkness.
“I hate the idea of worming down through a maze of fissures and caves,” the android muttered. “I’d rather take my chance in free space.”
“It’s our only possible way to the radium deposit,” Curt answered determinedly. “I brought along a radioscope, and with it for guidance we should be able to find a way down through the labyrinth.”
He took the compact radioscope from the mass of equipment that Grag carried on his back. The transformers, condensers and other apparatus appeared to have suffered no harm during the adventurous flight.
Captain Future took his little hand krypton lamp from his belt and turned on its blue beam. He flashed it into the dark fissure. “We’d better start,” he warned. “We’ve a long way to go, down to that radium deposit.”
The labyrinth they followed now was a mere split in the rock, so narrow they must move in single file. Ponderous masses of half-dislodged Moon-rock hung over them, ready to crush them. Curt moved with extreme care as he led the way. He knew well how fatally easy it was to start one of the terrible lunar-rock slides.
The darkness became Stygian. Yet the intrepid quartet of man, robot, android and Brain continued to penetrate deeper. The crevasse debouched presently into a gloomy underground gallery with walls of black lunar basalt. A half dozen new fissures branched from this gallery.
“Which one of ‘em should we take?” Otho wondered.
“There’s no way of telling which is the best to follow.”
“Then let’s guess,” said Grag.
He pointed his metal arm at the fissures in turn and recited an ancient phrase. “My mother told me to take this one.”
“Your mother?” Otho laughed at the robot. “Why, your mother was a machine shop, and if you had a father he was an old riveting machine.”
“That’s better than having a rack of chemical bottles for ancestors, like you!” Grag snapped.
“Shut up, you two,” Captain Future ordered impatiently.
“We don’t have to guess — the radioscope will show us which way to follow.”
He consulted the little instrument. Its needle, swinging on its queer quadrant to point toward the radium ores deep below, swung downward now in a northeastern direction.
“The radium deposit is in that general direction,” Curt declared. “That second fissure leads most nearly that way.