DOC did not go directly to the barricade where the natives were holding Spad Ames" men back.
Instead, he turned off into the shaft down which he had seen the file of men come bearing the strange greenish-yellow chemical.
The shaft was narrow, crooked, the work of some prehistoric trickle of water. Once, when Monk happened to splash his flashlight beam upward, he stopped and pointed.
"Look up in there, Doc," he suggested.
High in a cranny overhead was a small vein of the greenish-yellow chemical.Doc said: "There were probably veins of the stuff all through this peak to begin with, and water washed it away, leaving this cavern. That underground river which comes out at the base of the cliff-you remember how cold the water was?"
"What has cold water got to do with it?"
"Come on. I may be able to show you."
The vague odor grew more noticeable as they progressed, and it dawned on the others why Doc Savage had come in this direction.
"That smell is getting strong enough that the dogs won"t be able to trail us," big-fisted Renny rumbled cheerfully.
They came to a larger chamber, a place so vast that its length dimension was lost in the mists, although its width appeared to be at least two hundred feet, Doc found upon scouting.
The left wall of the chamber was composed for the most part of the greenish-yellow chemical.
Several of the white-haired Indians were working with long sticks, digging holes, then prying loose lumps of the chemical. Their torches threw pale-red light.
"Come on," Doc whispered.
They moved very cautiously and, not using their flashlights, pa.s.sed the workers. The floor of the chamber slanted upward shortly, and they began to hear sounds of running water. Then they were climbing stones laid in masonry.
The dam reached nearly to the ceiling-there was, in fact, only a narrow aperture at the top, and that could be closed by a great pivoted stone slab of a door.
A small underground river was rushing down, beating against the dam, and glancing off into another channel.
"This must be the stream they used to close the secret entrance," Monk decided.
Doc voiced his own opinion. "At one time, the stream flowed into the cavern through which we just pa.s.sed. The natives managed to dam it and divert it into another arm of the network of caves, and made their secret entrance."
The bronze man was thoughtful a moment.
"That gave them access to the chemical deposit," he added. "And lately, they must have considered making arrangements with the outside world to market the chemical commercially."
Renny said: "Holy cow! What is the stuff, Doc?"
INSTEAD of explaining directly, the bronze man cleared up details that had been puzzling the others.
"Mark Colorado had some of the chemical at the Phenix Academy," the bronze man said. "There was a packing case in his room, so probably the stuff was shipped to him in that. He evidently planned to market it, as I said. It was an excellent idea, because no natural deposit of the stuff has been found anywhere else. A commercial mixture probably somewhat similar has recently been marketed, however."
"Wait a minute!" Renny exploded. "You say something similar to this stuff is on the market?"Doc Savage nodded. The others were staring at his bronze features, lined in flashlight glow.
"It has long been the dream of chemists to discover a refrigerant which could be safely handled," Doc said. "You are all familiar with dry ice, or solidified carbon dioxide, which has a temperature of one hundred and nine degrees below zero."
"What has dry ice got to do-" Renny paused, swallowed, said: "I begin to get this."
"The recently marketed material," Doc continued, "is a combination of bicarbonate of soda and other substances, which the formula owner is keeping secret, which forms a powder. When water is added to this powder, it becomes violently cold. One pound of it is claimed to have the cooling power of at least fifty pounds of ice."
They thought this over. A great deal was becoming clear.
"This greenish-yellow stuff," Monk said, "becomes cold when you add water to it."
"Very cold," Doc agreed. "As cold, apparently, as liquid air, the temperature of which is extremely low.
As you know, a piece of beefsteak, for instance, when dipped in liquid air, instantly becomes so cold that it is as hard as stone and may be broken like gla.s.s."
Monk gave a bark of astonishment. "That explains the so-called stone men! They were simply frozen with this stuff!"
"Exactly," Doc agreed grimly. "Water was added to the greenish-yellow chemical to put it in operation, then the stuff was poured over the men. As soon as it exhausts itself, the stuff doubtless evaporates, just as do liquid air and dry ice. Dry ice doesn"t melt, as you know; it evaporates."
"That smoking effect around the bodies that everybody thought had been turned to stone," Monk suggested, "was simply the intensely cold chemical still evaporating from the body and clothing. Right?"
Doc nodded.
Then the bronze man gave his idea of the explanation for the unusual climate of the valley.
"The deposit of this chemical must be enormous," he said. "Water seepage reaches it continually, and the intense cold escapes through cracks in the stone, in the form of the mists which we noticed."
"And the rain the old-timer, here, said they had so often-"
"Is simply due to the cold valley air condensing what moisture there is in the atmosphere. The normal process by which rain is formed, accelerated somewhat by the cold seepage from this deposit."
They heard shouting, then, and screaming. The cries, garbled by the fantastic acoustics of the cavern, were as weird as the howling of a coyote pack on a moonlight night. There were explosions. Shots.
More cries.
"Sounds as if Spad Ames had broken through," Doc said.
With the others, he raced back toward the tunnel intersection. As they pa.s.sed through the great chamber where the natives had been mining the cold chemical, they saw that the miners had deserted their tasks and raced away.
Doc knew, of course, that they had been planning to use the chemical to freeze Spad Ames and his men, if they tried to rush the barricade.Apparently they had not been very successful.
THE fighting was furious in the main tunnel leading to the barricade. And the natives were retreating.
"Back!" Doc warned.
The bronze man had a few high-explosive grenades left. He ran down the subterranean pa.s.sage a short distance-not toward the fighting, but in the direction of the valley. He covered fifty yards, selected his spot, put one of the grenades in a crack in the wall, then whirled and ran back.
"Get down!" he rapped at the others.
The explosion ripped out, followed by a sound as if broken gla.s.s was being ground together, and the roof came down at that point. Rock dust boiled in the glare of their flashlights, mixing darkly with the lighter foglike vapor that came from the cold chemical.
Monk didn"t approve. "Blazes!" he howled. "Now we"re blocked off from the valley!"
"So is Spad Ames," Doc said grimly.
The first cl.u.s.ter of retreating white-haired Indians raced past. Doc and the others, extinguishing their flashlights and flattening against the side wall, escaped notice. The fleeing group reached the point where the roof had collapsed, instantly set up a terrified bedlam of howling.
"They seem a little disturbed," Monk said.
"Sh-h-h, you homely missing link!" Ham warned. "They find us, and we"ll be disturbed, too!"
The fugitives came racing back, dived into the tunnel which led to the huge chamber and the chemical deposit. Other natives in flight appeared, and followed them. The word had evidently gone down the line, in the strange gobbling language, that the other tunnel was blocked.
Doc watched them flee past. Except for running sounds the defenders made, comparative silence had fallen.
The last man in flight, it developed, was Mark Colorado. He must have recovered from the anaesthetic, followed the dogs as they trailed Doc and the others to the subterranean pa.s.sages, and joined the defenders.
Doc stepped out, grasped Mark Colorado"s arm. The bronze man put a flash on his own face so the other would recognize him.
"Oh-we knew you must be in here somewhere!" Mark Colorado gasped. "We-you"ve got to help us!"
"What happened?"
"They had poison gas. We were holding them back at a long shaft by rolling stones, until we could get ready to use the freezing stone upon them. The shaft was crooked, and they could not shoot the grenades to the top. But they caught a badger."
"Badger?"
"Yes. Tied a poison gas bomb to the badger, then turned the animal loose, and the scared creature climbed up the shaft. It was among us before we knew it. Half-half of our men are dead."Doc said: "Come on. We can"t hold them off here."
They followed the natives who had fled toward the great chamber, one side of which was composed of the vast deposit of cold chemical.
"We can get out into the valley by this route?" Doc asked.
"How-how did you know that?"
"The breeze. There is a strong draft through here. There has to be an opening somewhere beyond."
"Yes," Mark Colorado explained. "There is a dam across the river, and we can follow the river for a short distance, then there is another opening which leads into the valley."
They could hear the Spad Ames crowd behind them.
WHEN they were half across the great room, they were shot at. One of Spad Ames" men did the firing, using an automatic rifle. The bullets shrieked very close, and clamor of the weapon in the cavern was ear-splitting. They extinguished their lights, scattered.
"Get to the dam as quick as you can!" Doc shouted.
They raced forward. Renny became confused in the intense darkness, and ran against the chemical deposit with one hand, and there was enough perspiration on his skin to cause the stuff to induce terrific cold that felt as if a white-hot iron had touched his fingers. He howled in pain.
Doc showed a light briefly. Renny joined them. They scrambled up the steep stone backslope of the dam, found the narrow opening, and crowded through.
There was a native with a torch and a club on the other side. He snarled, lifted the club. Mark Colorado knocked him down, then barked at the man in their lingo.
"I told him," Mark Colorado explained, "to get the others out of here. Or do you want them to stay and help fight?"
"Tell them to get out," Doc directed. "You can stay and act as guide, if you don"t mind."
Mark Colorado shouted directions, and the native retreated, joining the others. The sounds they made grew fainter.
There were other noises, however, on the other side of the dam.
"Spad Ames and Locatella are coming!" Monk barked.
"Get back," Doc directed. "Get off this dam."
Then the bronze man sent a loud shout back into the great cavern.
"Ames!" he shouted. "Spad Ames!"
Spad Ames answered profanely, said: "d.a.m.n us! We"ve been wonderin" what happened to you!"
Doc yelled: "Get back! Don"t try to rush us! We"ll give you that one chance."
Spad Ames swore. Then he laughed. And he drove the beam of a powerful searchlight against the dam.
He made a mistake about the nature of the dam proving that he had apparently never been in this part ofthe underground labyrinth before.
"They got a barricade!" he yelled. "Blow it down, guys!"
Doc moved. He moved at least as fast as ever before in his life, and retreated from the dam. He splashed into the river, crossed it, joined the others, shouted: "Run! They"re going to blast the dam!"
The others were already running.
Spad Ames" bomb, evidently a big grenade thrown by hand, let loose a ripping crash. They had pitched it through the aperture in what they thought was a barricade, not a dam, and the thing had landed in the water. Spray flew over Doc and the others. The dam came apart.
For a few minutes, there was only rushing water.
Then the shrieks began coming. And the vapor. The cold. The incredibly agonizing cold. The yells grew more horrible.
The bitter cold kept increasing.
"Run!" Doc warned. "There is a tremendous deposit of that chemical. We might be frozen if we stay here."
They raced, falling frequently, through the cavern pa.s.sage.
After a while there were no more shrieks behind them.
And later they came out into the misty pleasant darkness of the valley.