"What, climb that mountain?" demanded Stacy.
"Surely. You are not afraid of a mountain, are you?" demanded Tad.
"I'm not afraid of---of anything, but I'm delicate, I tell yau."
"Just the same, you'll pack about fifty pounds up the side of that hill," jeered Ned Rector.
The pack mules had not yet come up with their driver. The party foreseeing this, had brought such articles as would be needed for the night. Taking their blankets and their rifles, together with food and wood for a fire, they began the slow, and what proved to be painful, ascent of Sunset Mountain.
A lava field stretched directly in front of them, barring the way. Its forbidding surface had been riven by the elements until it was a perfect chaos of black tumult. By the time the Pony Rider Boys had gotten over this rough stretch, they were ready to sit down and rest. Nance would not permit them to do so. He said they would have barely time to reach the crater before dark, as it was, and that they must make the best speed possible. No one grumbled except Stacy, but it was observed that he plodded along with the others, a few paces to the rear.
The Professor now and then would point to holes in the lava to show where explosions had taken place, bulging the lava around the edge and hurling huge rocks to a considerable distance. As they climbed the mountain proper they found that Sunset, too, had engaged in some gunnery in those far-away ages, as was shown by many lava bombs lying about the base.
The route up the mountain side was over a cider-buried lava flow, the fine cinders under foot soon making progress almost a torture. Tad was the first to stand on his head as his feet went out from under him. Stacy, in a fit of uproarious laughter, did the next stunt, that of literally standing on his right ear. Chunky tried to shout and got his mouth full of cinders.
"I'm going back," howled the fat boy. "I didn't come up here to climb slumbering volcanoes."
"I'll tell you what I'll do, I'll carry you, Stacy," said Tad, smiling and nodding toward the cinder-blackened face of his companion.
"You mean it?"
"Of course I mean it."
"I guess I can walk. I'm not quite so big a baby as that."
"I thought so. Have your fun. If you get into trouble you know your friend, Tad Butler, is always on the job."
"You bet I do. But this is an awful climb."
It was all of that. One step upward often meant a slide of several short steps backward. The Professor's face was red, and unuttered words were upon his lips. Jim Nance was grinning broadly, his whiskers bobbing up and down as he stumbled up the side of Old Sunset.
"I reckon the tenderfeet will get enough of it before they get to the Canyon," chuckled the guide.
"Say, Mr. Nance, we don't want to Mister you all the time. What shall we call you for short?" asked Tad Butler.
"Anything you want."
"What d'ye say if we call you Whiskers?" called Stacy.
"Stacy!" rebuked the Professor sternly.
"Oh, let the little tenderfoot rant. He's harmless. Call me Whiskers, if it does ye any good."
"I'm no tenderfoot," protested Chunky.
"Nor be I all whiskers," returned the guide, whereat Chunky's face turned red.
"I guess we'll call you Dad, for you'll have to be our dad for some time to come," decided Tad.
"That'll be all right, providing it suits the fat little tenderfoot."
Stacy did not reply to this. He was having too much trouble to keep right side up just then to give heed to anything else.
"Go zig-zag. You'll never get to the top this way," called Tad. "You know how a switchback railroad works? Well, go as nearly like a switch-back as possible."
"That's a good idea," agreed Dad. "You'll get there quicker, as the young gentleman says."
Tad looked at his companions, grinning broadly. As they got nearer to the top the color of the cinders changed from black to a brick red. They began to understand why the peak of Sunset always presented such a rosy appearance. It was due to the tint of the cinders that had been thrown from the mouth of the volcano ages ago.
"We have now entered the region of perpetual sunset," announced the Professor.
Chunky took advantage of the brief halt to sit down. He slid back several feet on the treacherous footing.
Still further up the mountain took on a rich yellow color, but near the rim it was almost white. It was a wonderful effect and caused the Pony Riders to gaze in awe. But darkness was approaching rapidly. The guide ordered them to be on the way, because he desired to reach the rim of the crater while they still were able to see. What his reasons were the boys did not know. They took for granted that Dad knew his business, which Dad did. He had spent many years in this rough country and knew it well. The Grand Canyon was his home. He lived in it the greater part of the year. When winter came, Dad, with his mustang, his cattle and equipment would descend into the Grand Canyon far from snow and bitter cold into a land of perpetual summer, where, beside the roaring Colorado, he would spend the winter alone with his beloved Canyon.
Dad's was a strange nature. He understood the moods of the great gash in the plateau; he seemed literally to be able to translate the mysterious moans and whispers of the wind as it swirled between the rocky walls and went shrieking up the painted sides of the gulches.
But of all this the boys knew nothing as yet. It was all to be revealed to them later.
"You'll have a look over the country tomorrow," said Dad.
"Where is the Canyon?" asked Tad, eager for a view of the wonderful spot.
"You'll get a glimpse of it in the morning. You'll know the place when you get to it. Here we be at the top. There's the hole."
Chunky peered into the crater rather timidly.
"How do you get down?" he asked.
"Slide," answered Ned.
"I can do that, but what's at the bottom?"
"The same thing. Cinders and lava," answered Tad. "What would you expect to find in a volcano?"
"I'd never expect to find Stacy Brown in one, and I'm not sure that I'm going to."
"All hands follow me. There's no danger," called the guide, shouldering his pack and leaping and sliding down the sharp incline. He was followed by the boys with shouts of glee. They went tumbling head over heels, laughing, whooping, letting off their excess steam. The Professor's grim face relaxed in a smile; Dad's eyes twinkled.
"We'll take it out of them by and by," he confided to the Professor.
"You don't know them," answered Professor Zepplin. "Better men than you or I have tried it. Remember, they are young. We are old men. Of course, it is different with you. You are hardened to the work, still I think they could tire both of us out."
"We'll see about that."
"Whoop-e-e!" came the voice of Tad Butler far below them. "I'm at the bottom. Any wild animals down here, Dad?"
"Only one at present. There'll be three more in a minute."
"Six, you mean," laughed Tad.
The others had soon joined him.
"How far are we from the surface?" asked Walter.
"About five hundred feet down. We're in the bowels of the mountain for sure, kid," answered the guide.
"That's pretty tough on the mountain. I'm afraid it will have a bad case of indigestion," laughed Tad.
"You needn't be. It has swallowed tougher mouthfuls than you are," returned the guide, ever ready with an answer.
"Dad's able to give as good as you send," laughed Ned.
"That's good. All the better for us," nodded Tad. "What about some light?"
"Unload the wood from your packs. This is where you are glad you did pack some stuff."
In a few minutes a fire was blazing, lighting up the interior of the crater. The boys found themselves in a circular opening of almost terrifying roughness and something like a quarter of a mile across. Here, in ages past, the forces of Nature had been at work with fearful earnestness. Weird shadows, mysterious shapes, somewhat resembling moving figures, were thrown by the flickering blaze of the camp fire. While the boys were exploring the crater Dad was busy getting the supper ready, talking with Professor Zepplin as he worked.
The voices of the boys echoed from side to side of the crater, sounding strange and unreal. The call to supper put an end to their explorations. They sat down with keen edges to their appetites. It was their first meal in the open on this journey. All were in high spirits.
"I think we should agree upon our work for the future," declared the Professor.
"Work?" exclaimed Chunky, opening wide his big eyes.
"Yes. It is not going to be all play during this trip."
"We are willing to do our share," answered Ned.
"Yes, of course we are," chorused Walt and Stacy, though there was no enthusiasm in the fat boy's tone.
"I am of the opinion that you boys should take turns in cooking the meals, say one boy to cook for an entire day, another to take the job on the following day."
"I'll cook my own," declared the guide. "No tenderfoot experiments in my chuck."
"They know how to cook, Mr. Nance," explained the Professor.
"All right; they may cook for you," said the guide, with a note of finality in his tone. He glanced up at the sky, held out his hand and shook his head. Tad observed the movement.
"What is it?" asked the boy.
"It's going to snow," said Dad.
Tad laughed, glancing at his companions.
"What, snow in June?" questioned Stacy.
"You must remember that you are a good many thousand feet up," the Professor informed him.
"Up? I thought I was down in a crater."
"You are both up and down," spoke up Tad.
"Yes, I'm usually up and down, first standing on my feet then on my head," retorted Stacy. "How are we going to sleep?"
"Same as usual. Pick out your beds, then roll up in your blankets," directed Dad. "You are used to it, eh?"
"Well," drawled Chunky, "I've slept in a good many different kinds of beds, but this is the first time I ever slept in a lava bed."
True to Dad's prophecy, the snow came within half an hour.
"Better turn in before the beds get too wet," advised Dad.
All hands turned in. Sleep did not come to the boys as readily as usual. They had been sleeping in real beds too long. After a time the snow changed to rain in the warmth of the crater. Chunky got up disgustedly.
"I'm tired of sleeping in the bath tub," he declared. "Think I'll move into the hall bedroom."
Chuckles were heard from beneath other blankets, while Stacy, grumbling and growling, fussed about until he found a place that appeared to be to his liking.
"When you get through changing beds perhaps you will give us a chance to go to sleep," called the guide.
Stacy's voice died away to an indistinct murmur. Soon after that quiet settled over the dark hole in the mountain. The rain came down harder than ever, but by this time the Pony Rider Boys were asleep. They neither heard nor felt the water, though every one was drenched to the skin.
Toward morning Tad woke up with a start. He thought something had startled him. Just then an unearthly yell woke the echoes of the crater. Yell upon yell followed for the next few seconds, each yell seeming to be further away than the preceding one, and finally dying out altogether.
"It's Chunky!" shouted Tad, kicking himself free of his blankets and leaping up. "Some thing's happened to Chunky!"