"Woof!" exclaimed Ned Rector.
"Oh!" cried Walter Perkins.
"Good boy! Hang on!" shouted Tad encouragingly.
It is doubtful whether Stacy heard either the words of warning or those of encouragement from Tad, for at that moment Stacy's feet were up in the air. The pinto had leaped forward like a shot the instant it felt the touch of the rope. Of course Chunky, who had clung to the rope, went along at the same rate of speed.
A great cloud of dust rose from the corral. The mustang was darting here and there, bucking, squealing and kicking. In a moment most of the other mustangs were doing likewise. The owner of the herd, calling to the Professor, darted out, leaving one bar of the fence down. Professor Zepplin, becoming confused, missed his way and found himself penned into one corner at the far side, almost the center of a circle of kicking mustangs.
Tad saw the danger of their companion almost at once. The lad leaped down, and darting among the kicking animals, made his way toward the Professor just as Stacy's mustang leaped the bars. Stacy's toes caught the top rail, retarding his progress for the briefest part of a second, then he shot out into the air after the racing mustang.
"Leggo!" roared the boys.
"Let go!" shouted the guide. "The little fool! Doesn't he know enough to come in out of the wet?"
"You'll find he doesn't, sir. Your troubles have only just begun. You'll be demanding an increase of wages before you have followed Stacy Brown for a full twenty-four hours," prophesied Ned.
In the meantime Tad had reached the Professor, regardless of the flying hoofs about him. With his rope the boy drove the animals off just in time. Somehow they seemed to have taken it into their heads that the Professor was responsible for their having been disturbed and they were opening their hoof batteries upon him. They gave way before the resolute young Pony Rider almost at once. They recognized that this slender young plainsman and mountaineer was unafraid.
The Professor was weak in the knees by the time he had been led out.
"I didn't know you were in there," apologized Nance.
"Where's Stacy?" was the Professor's first question.
"He's gone by the air line," answered Walter.
While all this had been taking place Chunky had continued in his mad flight for a short distance. He had a long hold on the rope by which the mustang was hauling him. The wary beast, espying a tree whose limbs hung low, changed his course and darted under the lowest of the limbs. Its intention was plain to those who knew the habits of these gentle beasts. The mustang intended to "wipe" the Pony Rider boy free of the line.
Just before reaching the low-hanging limb the pinto darted to one side, then to the other after an almost imperceptible halt. The result was the rope was drawn under the low limb. A quick leap on the part of the mustang, that exhibited almost human intelligence by this manoeuvre, caused Chunky to do a picturesque flop over the limb, falling flat on his back on the other side. This brought the mustang to a quick stop, for the rope had taken a firm hitch around the limb.
The sudden jolt and stoppage of his progress threw the mustang on his nose, where he poised for a few seconds, then he too toppled over on his back.
The owner of the herd was screaming with, merriment, Jim Nance was slapping his sides as he ran, while the Professor was making for the fat boy with long strides.
Tad reached Stacy first. The fat boy lay blinking, looking up at him. Stacy's clothes were pretty well torn, though his body did not seem to be harmed beyond the loss of considerable skin.
"Let me have that rope," commanded Tad.
"N-n-no you don't."
"Let me have that rope, I tell you. I'll attend to the pinto for you."
"Here, give it to me," ordered Jim Nance, reaching for the rope which Tad Butler had taken.
"I can handle him, Mr. Nance."
The "handling" was not easy. Tad was hauled over the best part of an acre of ground ere he succeeded finally in getting an opportunity to cast his own rope. When, however, he did make the cast, the rope caught the pinto by a hind foot, sending the stubborn little beast to the ground. Then Tad was jerked this way and that as the animal sought to kick the foot free.
"Grab the neck rope some of you," he cried.
Nance was the first to obey the command. It was the work of but a moment temporarily to subdue the pinto.
"Take him back. We don't want the critter," ordered the guide.
"I---I want him," declared Stacy, limping up to the former sleepy beast.
"I'll break him so I guess Stacy can ride him," said Tad. "Ned, will you fetch my saddle and bridle? I can't let go here just yet. Has this fellow ever been ridden?" demanded the boy, looking up at the owner.
"I reckon he has, but not much."
"Why did you let Brown rope the pinto, then?"
"He said he wanted him."
"Let him up," directed Tad. The mustang had another spell, but ere he had finished his bucking Tad had skillfully thrown the saddle on and made fast the saddle girth at the risk of his own life. Next came the bridle, which was not so easily put in place. It was secured at last, after which the lad stepped back to wipe the perspiration from his face and forehead. Dark spots on his khaki blouse showed where the sweat had come through the tough cloth.
"Now I'll ride him," Butler announced.
For the next quarter of an hour there followed an exhibition that won the admiration of all who saw it. All the bucking and kicking that the pinto could do failed to unseat Tad Butler. When finally he rode back to the group, Mr. Mustang's head was held straight out. Once more the sleepy look had come into his eyes, but it was not the same crafty look that had been there before. He was conquered, at least for the time being.
"Now, Chunky, you may try him."
"What do you think of that for riding?" demanded Stacy, turning to the guide.
"Oh, he'll ride one of these days," answered the guide.
"I believe you're a grouch," snorted the fat boy, as he swung into the saddle, quickly thrusting his toes into the stirrups, expecting to be bucked up into the air.
But nothing of the sort followed. The mustang was as meek as could be. Stacy rode the animal up and down the field until satisfied that the pinto was thoroughly broken. Stacy was an object of interest to all. He was a very much banged-up gentleman, nor was Tad so very far behind him in that respect.
Young Butler chose for his mount a mustang with a white face. Already Tad had decided to call him Silver Face. The two very quickly came to an understanding, after a lively but brief rustle about the enclosure. After this Tad roped out the pintos for the others of his party. This done, the boys took their mustangs out into the field, where they tried them out. The spectators were then treated to an exhibition of real riding, though the Pony Riders were not doing this for the sake of showing off. They wanted to try their mounts out thoroughly before deciding to keep those they had chosen.
At last they decided that the stock could stand as picked out, with the exception of Walter Perkins's mustang, which went lame shortly after the boy had started off with him.
"I guess we are all right now," announced Tad, riding up to where the Professor and Jim Nance were standing. "Has either of you any suggestions to offer?"
"Hain't got no suggestions to offer to the likes of you," grumbled the guide. "Where'd you learn to ride like that?"
"Oh, I don't know. It came natural, I guess," replied Tad simply. "The others ride as well as I do."
"Then we'll be moving. I reckon you are figgering on gitting started to-day?"
"Yes, we might as well be on our way as soon as you are ready, Mr. Nance," agreed the Professor.
"How about the pack train?" asked Tad.
"The mules are all ready," answered the guide.
The lads rode their new horses back to Flagstaff. None cared to ride in the buckboard long as there was a horse to ride. Even the Professor thought he would feel at home in the saddle once more. Nance observed that though Professor Zepplin was not the equal of the Pony Riders on horseback, yet he was a good man in the saddle. Nance was observing them all. He knew they would be together for some weeks and it was well to understand the peculiarities of each one of the party at the earliest possible moment.
Reaching town the party found that the entire equipment for the pack train had been gotten in readiness. There remained but to pack the mules and they would be ready for their start. This was done with a will, and about two o'clock in the afternoon the outfit set off over the stage road, headed for the Grand Canyon.
It was a happy party, full of song and jest and joy for that which was before them. The way led through the Coconino Park. Some three miles out they halted at the edge of a dry lake basin, in the centre of which was a great gaping hole. The Professor pointed to it inquiringly.
"There was a lake here up to a few years ago," explained Jim. "Bottom fell out and the water fell in. Ain't no bottom to it now at all"
"Then---then the water must have leaked out on the other side of the world," stammered Chunky, his eyes big with wonder.
"I reckon it must have soused a heathen Chinee," answered Nance, with a grin.
"Pity it didn't fall out the other way and souse a few guides, eh?" questioned the fat boy, with a good-natured grimace at which Nance laughed inwardly, his shaking whiskers being the only evidence of any emotion whatever.
"Up there is Walnut Canyon," explained Jim. "Cliff dwellers lived up there some time ago."
"Yes, we met some of them down south," nodded Chunky.
"You mean we saw where they once lived long, long ago," corrected Professor Zepplin.
"Yes, we saw where they lived," agreed Stacy.
The way led on through a forest of pines, the trail underfoot being of lava, as hard and smooth as a road could be. They were gradually drawing nearer to Sunset Mountain. After a time they turned off to the right, heading straight for the mountain.
Tad rode back to the Professor to find out where they were going.
"I thought you boys might like to explore the mountain. You will find some things there well worth scientific consideration."
"Yes, sir; that will be fine."
"You know the mountain was once a great volcano."
"How long ago?" interrupted Stacy.
"A few million years or so."
"Mr. Nance must have been a boy in short trousers then," returned Stacy quizzically. The guide's whiskers bristled and stood out straight.
The road by this time had lost its hardness. The ponies' hoofs sank deep into the cinders, making progress slow for the party. They managed to get to the base of the mountain, but the mustangs were pretty well fagged. The animals were turned out for the night after having been hobbled so that they could not stray far away.
"Now each of you will have to carry a pack," announced the guide. "I will tell you what to take."
"Why, where are we going?" asked Tad.
"We are going to spend the night in the crater of the extinct volcano," said the Professor. "Will not that be a strange experience?"
"Hurrah for the crater!" shouted the boys.
"Speaking of volcanoes, I wish you wouldn't open your mouth so wide, Ned. It makes me dizzy. I'm afraid I'll fall in," growled Chunky.