Faster than he had ever travelled before in his life Nat was hurtled along down the flume. Water dashed upward into his face, half choking him and occasionally his board would hit the wooden side with a bump that almost threw him off. His knuckles were bruised and bleeding and his head dizzy from the motion. It was the wildest ride that the lad, or any other lad for that matter, had ever undertaken.

Suddenly, ahead of him—above the noise of the rushing water—came another sound, a deep-throated, sullen thunder. As he shot along with the speed of a projectile, Nat realized what the strange sound betokened. The end of the flume. Cal had told them that the raised water-course discharged its contents into a big pool at that point. With a sudden sinking of the heart Nat realized that he had forgotten to inquire how high the drop was. If it was very high—or if there was but little water in the pool below the flume—he would be dashed to pieces, or injured so that he could not swim, and thus drown.

But even as the alarming thought was in his mind, Nat felt himself shot outward into space. Instinctively his hands came together and he dived downward, entering the water about twenty feet below him, with a clean dive.

For a space the waters closed above the lad's head and he was lost to view in the moonlit pool. When he came to the surface, out of breath and bruised, but otherwise uninjured, he saw that he was in what had formerly been used as a "collection-pool" for the logs from the forest above. He struck out for the shore at once and presently emerged upon the bank. But as he clambered out, the figure of a Chinaman who had been seated fishing on the brink galvanized into sudden life. The Mongolian was poaching in private waters under cover of the darkness and was naturally startled out of a year's growth at the sudden apparition.

With an ear-splitting screech the Mongolian leaped about three feet into the air as if propelled by a spring, and then, with his stumpy legs going under him like twin piston rods, he made tracks for the town.

"Bad spill-it! Bad spill-it! He come catchee me!" he howled at the top of his voice, tearing along.

As he dashed into the town a tall man dressed in Western style, and with a determined, clean-cut face under his broad-brimmed sombrero, stepped out of the lighted interior of the post-office, where the mail for the early stage was being sorted.

"Here, Sing Lee," he demanded, catching the astonished Chinaman by the shoulder and swinging him around, "what's the matter with you?"

"Wasee malla me, Missa Sheliff? Me tellee you number one chop quickee timee. Me fish down by old lumbel yard and me see spill-it come flum watel!"

"What?" roared Jack Tebbetts, the sheriff, "a ghost? More likely one of Morello's band; I heard they were around here somewhere. But hullo, what's this?"

He broke off as a strange figure came flying down the street, almost as fast as the fear-crazed Chinaman.

"Wow!" yelled the sheriff, drawing an enormous gun as this weird figure came in view, "Halt whar you be, stranger? You're a suspicious character."

Nat, out of breath, wet through, bruised, bleeding and with his clothing almost ripped off him, could not but admit the truth of this remark. But as he opened his mouth to speak a sudden dizziness seemed to overcome him. His knees developed strange hinges and he felt that in another moment he would topple over.

The sheriff stepped quickly forward and caught him.

"Here, hold up, lad," he said crisply, "what's ther trouble?"

"One o'clock. We ought to be hearing from Nat soon."

Cal put his old silver watch back in his pocket and resumed his anxious pacing of the floor. The others, in various attitudes of alertness, were scattered about the place. Since Nat's departure they had been, as you may imagine, at a pretty tight tension. Somehow, waiting there for an attack or for rescue, was much more trying than action would have been.

"Do you guess he got through all right?" asked Joe.

"I hope so," rejoined Cal, "but it was about as risky a bit of business as a lad could undertake. I blame myself for ever letting him do it."

"If Nat had his mind made up you couldn't have stopped him," put in Joe earnestly.

"H-h-h-hark!" exclaimed Ding-dong.

Far down the canyon they could hear a sound. It grew closer. For an instant a wild hope that it was the rescue party flashed through their minds. But the next instant a voice hailed them. Evidently Col. Morello had made up his mind that a siege was too lengthy a proceeding.

"I will give you fellows in the hut one chance," he said in a loud voice, "give up that boy Nat Trevor and the sapphires and I will withdraw my men."

Cal's answer was to take careful aim, and if Joe had not hastily pulled his arm down that moment would have been Morello's last. But as Cal's white face was framed in the dark window a bullet sang by viciously and showered them with splinters.

"That's for a lesson," snarled Morello, "there are lots more where that came from."

But as he spoke there came a sudden yell of alarm from his rear.

"We're attacked!" came a voice.

At the same instant the sound of a distant volley resounded.

"Hooray! Nat made good!" yelled Cal, leaping about and cracking his fingers.

The next instant a rapid thunder of hoofs, as the outlaws wheeled and made off, was heard. As their dark forms raced by, the posse headed by Sheriff Tebbetts and Nat, fired volley after volley at them, but only two fell, slightly wounded. The rest got clear away. A subsequent visit to their fortress showed that on escaping from the posse they had revisited it and cleaned all the loot out of it that they could. The express box stolen from Cal's stage was, however, recovered.

As the posse galloped up, cheering till the distant canyons echoed and re-echoed, the besieged party rushed out. They made for Nat and pulled him from his horse. Then, with the young Motor Ranger on their shoulders, they paraded around the hut with him, yelling like maniacs, "'For he's a jolly good fellow'!"

"And that don't begin to express it," said the sheriff to himself.

"He's the grit kid," put in one of the hastily-gathered posse admiringly.

And the "Grit Kid" Nat was to them henceforth.

The remainder of the night was spent in the hut, Nat telling and retelling his wild experience in the flume. The next morning the posse set out at once at top speed for the fortress of Morello, the sapphire chest being carried in the auto which accompanied the authorities. Of course they found no trace of the outlaws; but the place was destroyed and can never again be used by any nefarious band.

Nat and his friends were anxious for the sheriff to take charge of the sapphire find, but this he refused to do. It remained, therefore, for the Motor Rangers themselves to unravel the mystery surrounding it.

How they accomplished this, and the devious paths and adventures into which the quest led them, will be told in the next volume of this series. Here also will be found a further account of Col. Morello and his band who, driven from their haunts by the Motor Rangers, sought revenge on the lads.

Having remained in the vicinity of Big Oak Flat till every point connected with Morello and his band had been cleared up, the boys decided to go on to the famous Yosemite Valley. There they spent some happy weeks amid its awe-inspiring natural wonders. With them was Herr Muller and Cal. Bismark, as Cal had foretold, returned to the hotel at Lariat and Herr Muller got his money.

But all the time the duty which devolved upon the Motor Rangers of finding Elias Goodale's heirs and bestowing their rich inheritance on them was not forgotten. Nat and his companions considered it in the nature of a sacred trust—this mission which a strange chance had placed in their hands. How they carried out their task, and what difficulties and dangers they faced in doing it, will be related in "The Motor Rangers on Blue Water; or, The Secret of the Derelict."

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