"Why not?" Rick said. He took a notebook from his pocket and began to write the dots and dashes of the message that the scientists were sending. "Here." He handed the book to Scotty. "Hold the key twice as long for a. dot as you do for a dash. That's all there is to it."

Scotty scratched his head over the scrawl on the page and said he would do his best. "We should stand watches on this thing, don't you think, Professor Zircon?"

Zircon nodded - without much enthusiasm, Rick noted. Their signal would be pitifully weak at best and he doubted that it was getting out at all.

The black curtain that was the Tibetan night dropped suddenly, and soon it was difficult to make out the figure of Julius Weiss, crouched at the key.

"I'll stand the first watch," Zircon said, "then you can take over, Rick."

"And I'll wake you about dawn," Rick said to Scotty.

There was nothing more to be done. If their message was scaling the mountains that surrounded them, there was a faint hope.

If not...

Rick crawled into his sleeping bag and pulled it close about him. There was no friendly chat between him and Scotty tonight as there had been every night on the trail. He knew that Scotty wanted to be alone with his thoughts as he did with his.

They were rambling thoughts, of home and of all that had happened to them. He had a fleeting glimpse of the face of a little Hindu boy as he drifted into the half-world between sleep and wakefulness, and the last thing he heard was the radar key futilely tapping out: "Held... captive ... high ... plateau... lat.i.tude..."

CHAPTER XIX.

The Glorious Fourth

"HAPPY holiday, pall"

For a moment, Rick thought he was at home. Then he sat upright and looked into the face of Scotty, bending over him.

"Hey, why didn't you wake me for my watch?" he demanded.

Scotty grinned. "You looked like you were dreaming of ice cream. I remember we always used to have ice cream on the Fourth of July!"

"Holy smokes!" Rick jumped from his sleeping bag. "This is the Fourth of July!"

"Yeah," Scotty said sourly. "Happy Independence Day."

"Only I'm not feeling very independent this morning," Rick remarked. He looked across the plateau at Zircon, still busily pumping away at the key. The big scientist tried to muster a grin and asked, "Where are your fireworks?"

"That would be appropriate, wouldn't it?" Rick said.

"Shall we drop down to the drugstore and get some?"

The reminder of home sobered everyone for a moment and then Scotty spoke up. "Hey, that reminds me. Barby gave us both a package that we were supposed to open today."

Rick started to grin. "Say, do you suppose that little monkey made us a present of ..." He leaped for the pile of equipment and started searching for the boxes that his sister had presented to them with such ceremony.

"Here's mine," he said finally, "but I don't see yours, Scotty."

"The heck with mine. Open it!"

Rick tore the paper from the box and removed the cover.

"Are they...?"

"They are ... fireworks!"

It was the first time any of them had laughed in a week, and the plateau rang with their boisterous howls.

Rick finally stopped laughing and looked into the box, and shook his head.

"Well, what did you expect to find, a rope ladder?" Scotty jeered.

"It would have been thoughtful of her. Maybe it's in your box," he answered.

"My box. Ha! I just remembered. My box was among that stuff that Sahmeed walked off with."

"Oh, well," Rick answered, "one six-incher is better than none." He drew one of the red firecrackers from the box and held it high.

"It may be our last Fourth, so why don't we show the Mongols how we celebrate a good, rip-roarin' Fourth back home," he said with false gaiety. He walked toward the edge of the plateau and looked over.

Far below, he could see two of the guards posted by the entrance in the base of the rock.

"As though we needed guarding," he commented.

Scotty's eyes were gleaming. "How good a shot are you?" he asked.

"What do you mean?"

Scotty pointed straight down at one of the dozing guards. "See how his leather armor is pulled away from the back of his neck?"

Rick looked. "Impossible," he said.

"Oh, yeah?" Scotty reached for the firecracker in Rick's hand. "Watch an expert," he chuckled.

Rick held a match while Scotty lit the firecracker, then watched his pal hold it over the edge of the plateau. Scotty squinted for a moment, then let the firecracker go. It started to turn over as it fell, then straightened out and plummeted straight to its target! With a shower of sparks, it went straight down the neck of the man and let go!

The Mongol leaped straight into the air and let out the most fearsome howl Rick had ever heard.

Scotty was convulsed with laughter. Zircon deserted his key, and Weiss hurried to the plateau edge as they realized what the boys had done. They all looked down at the guard, who was digging at the back of his armor and shaking his dagger up at them.

"Brother, if he could get his hands on you," Rick said.

"He seemed to know what it was," Scotty observed.

Weiss spoke up. "You forget," he said, "these people are from the land where firecrackers were invented ... China. It's an old story to them. A very old story."

They turned from the edge and walked back toward the box of fireworks.

"Well, I for one, don't see any sense in having a nice holiday spoiled, just because we're up here," Rick said, trying to speak lightly.

"Neither do I," Scotty replied. But Rick could tell that the excitement of his bull's-eye shot had worn off and his heart wasn't in it.

If they gave in to the gloom that was enveloping them, Rick realized their imprisonment would be even more of a torture than it was already. Hunger was nipping at his insides and would get worse as the day progressed. None of the others had mentioned being hungry or thirsty but he knew that all of them were. With what pa.s.sed for a laugh, he reached for the box of fireworks and beckoned Scotty to the edge of the cliff. They tried to amuse themselves by dropping the smaller crackers over the side for a while, but this soon palled on them.

"Seems like a waste of time," Scotty sighed.

"We have nothing but time." The moment he said it, Rick knew he had queered any holiday atmosphere left in either of them. They dropped the fireworks to the ground and walked to the radar key over which Weiss was now crouching.

They stood there silently, watching Weiss's fingers tap out the message though every last one of them had lost hope that it would ever reach the outside world.

"If we could only do something," Scotty suddenly exploded.

It was not his pal's nerve breaking, Rick knew. Scotty meant that he wanted to go down fighting.

"Look, why don't we make this Fourth of July a real whooper-dooper?" Rick suggested.

"Aw, Rick," Scotty objected.

"I think that's a wonderful idea," Weiss spoke up suddenly, surprising them both.

"So do I!" Zircon added. "What's on your mind, Rick?"

"Well," he began, "here is the field telephone." He reached into the equipment box and lifted it out. "We can use the head of it as a microphone."

Light was dawning on Zircon now. "I see. And you want to attach it to an amplifier and speaker, and really give them a grand explosion."

"Wait," Weiss interrupted. "We were going to use that field telephone for communicating between our radar equipment and our camp ... when we got there."

"Optimist!" Zircon snorted.

"Sure, let's do it." Scotty was enthusiastic now.

Zircon disengaged the amplifier from the radar equipment and started connecting it to the loudspeaker.

"That means no messages for a while," Weiss said worriedly.

"Let them wait," Zircon laughed recklessly. He seemed to be having as much fun as the two boys now.

Rick connected the makes.h.i.+ft microphone to the amplifier and speaker, and Zircon tied the whole into the wind-driven power supply.

"Good thing this is a ten-inch speaker," Rick grinned. "This is really going to make some noise!"

Weiss was rummaging nervously through the equipment. "I hope this turns out all right," he said.

"They'll never forget this Fourth of July." Zircon smiled. "Light your firecrackers, Rick."

Scotty held the microphone far away from him, and Rick held one of the larger crackers in a pair of pliers and lit it.

They held their ears as the firecracker fizzed. And then it exploded with a roar that startled even the scientists who thought they knew what the effect would be.

The blast rolled from the huge speaker in a thunderous wave that smashed against the rocky walls that imprisoned, seeming to gain volume as it bounced from ledge to ledge.

"Look at the Mongols," Scotty said, pointing down.

They looked, and saw terrified faces turned up to them.

"Whoopee! Do it again," Julius Weiss yelled.

They roared with laughter at the little man's sudden enthusiasm and then Rick said, "Why not make this one a whooper-whooper-dooper? Two of them at once!"

Zircon slapped Rick on the back in approval. Rick put two crackers within the jaws of the pliers. This time Scotty stretched his arm almost out of its socket to get away from the blast he knew would come. The fuses crackled as Rick touched the match to them and held the firecrackers toward the microphone.

With a roar, they went off, but the ocean of sound that welled from the speaker wiped the smiles off every face.

For as the reverberations rocketed across the city, they felt an ominous rumble. Rick saw Weiss staring beyond him to the left, and as he whirled around, his heart pounded.

A whole section of the mountain wall was slowly detaching itself from the sheer side and with gathering speed started to slip toward the floor of the valley. Then the side of the mountain disengaged itself completely and with a mighty roar plunged toward the earth.

With horror, Rick realized what they had done. Their Fourth of July celebration had set off a landslide! They were almost knocked from their feet as one half of the crumbling mountain hurled itself outward and landed with a deafening crash squarely in!

CHAPTER XX.

Return of the Great Khan

CHOKING clouds of dust rose from the floor of the valley and mushroomed out above the city. Their eardrums were still numbed by the mighty roar of the landslide, and below them they could see nothing through the haze.

Rock was still f ailing, and Rick breathed thankfulness that they could not see the havoc wrought on the Mongols by their innocently intended celebration.

No one spoke. It was impossible to put their anguish into words. They just stared down into the rising cloud of dust.

Finally Zircon muttered, "I didn't want this to happen. Even to be free."

"And especially since it serves no purpose," Weiss added, almost in a whisper.