which changed to pink, then to opal, as the coming sun tinged the low-lying clouds. The animal and bird life began to stir, preparing to greet the beauty of the dawn, or rather, to start on their affairs of the day, for it is likely that the denizens of the prairie had as little thought for the glory of the sunrise as had Injun and Whitey, whose minds were firmly fixed on train robbers.

When the light was full, the boys drew up, and looked off toward the southwest. Whitey had been depending on Injun's never-failing sense of direction to carry them aright. This ability to point toward any point of the compass, in the dark, was one of Injun's gifts—though he didn't know what a compass was. And sure enough, away off there against the gray of the clouds was a line of high, tiny crosses, telegraph poles, near which stretched the tracks of the road.

When he saw them, Whitey could not resist a whoop of joy. "If we ride straight for them, how far do you think we'll be from the water tank?" he asked.

"Mebbe one mile, mebbe two," replied Injun, who seldom committed himself to an exact answer.

"That's all right, come on!" cried Whitey, and they galloped straight for the railroad.

When they reached the tracks, they dismounted and tied their ponies to neighboring telegraph poles, fearing the effect the noise of the train would have on the spirited animals. Then the boys went to the roadbed to await the coming of the train. The line stretched straight toward the west, until the rails seemed to join in the distance. But toward the east was a curve as the road approached a gully, at the bottom of which was a creek. It was from this creek that the water was drawn for the tank.

The sunrise had seemed to promise a fair day, but the promise failed, for a mist was forming over the plains. The train was not in sight, and Whitey kneeled, and placed an ear to the track, knowing that he could detect the vibration caused by the train before it appeared.

He rose and nodded his head. "I hear it," he said. For once Whitey had it on Injun. He knew about railroads and Injun didn't.

"Light the lantern," said Whitey. Then he began to laugh.

Injun gazed at the lantern, then at Whitey. He could see no cause for laughter.

"I was wise when I suggested that lantern," said Whitey. "I never thought that it would be daylight, and its light wouldn't show."

Injun almost smiled.

"What we ought to have is a red flag," Whitey continued. "That's the proper thing to signal a train with in daytime."

Injun grunted, and Whitey considered the matter. "I have it! Your shirt!" he cried. "It's pink, close enough to red. We'll wave that."

Injun grunted again and looked doubtful. "Me get 'im back?" he asked. Injun didn't care any less for that shirt than he did for his pinto or his rifle—and he cared more for it than for his interest in the gold mine.

"Sure, you'll get it back," said Whitey, and without a word Injun took off the shirt and handed it to Whitey.

The boys gazed anxiously toward the west. Whitey thought of the three armed men, who now probably had handkerchiefs tied over their faces, and were lying in wait in the gully. Then of the oncoming train, with its unsuspecting passengers, and in the express car the bags of ore that were said to assay forty thousand dollars a ton. It wouldn't take much of that to make it worth while for the bandits to hold up the shipment.

Although the mist was getting thicker, it seemed singular that the train did not appear. The inaction of waiting was beginning to get on Whitey's nerves—and would have affected Injun's if he'd had any. At that, they had not been waiting very long, though they did not know it.

"It must be getting near. I'll listen again," said Whitey.

Whitey again placed his ear to the track, then looked up blankly. "It's stopped," he said, "Mebbe there's been an accident."

Injun knew a good deal about plains and woods, and animals and birds, but was rather in awe of trains. He gazed at Whitey's face, which wore the same blank look as his own, and ventured no opinion. Two sharp, faint sounds came from the east—something between the crack of whips and the popping of corks. They were followed by three more.

Injun knew about these. "Him shoot," he said.

The startled expression on Whitey's face gradually gave way to one of understanding and disgust. "They came from the water tank," he said. "Don't you see? We're late, and what I heard was the train going the other way. Then it stopped, and they're holding it up." And Whitey sat down on one of the rails, thoroughly disgusted.

For a while nothing was said. The disappointment was too great for words. The boys' chance for heroism had melted in the fog, which the mist had now become. Injun slowly put on his shirt. It was nothing but a garment now, no heroic rescue signal.

"I'll bet that clock at the ranch was wrong. It always is. I might have known it," Whitey said dejectedly. The thought of the loss of the gold was forgotten in his disappointment at failure. "I hope no one was hurt—I mean none of the trainmen or passengers," he added. "But I guess not. Those bandits had the drop on them, and they couldn't have put up much of a fight. How do you suppose we heard those shots? We must be at least a mile from the tank.

"Him fog," Injun answered. "Hear plain." And it is true that fog has a way of conveying sound.

An idea brought Whitey to his feet with a leap. "What fools we are to be sitting here!" he cried. "We'll follow those robbers. The people on the train won't do that. They've no horses."

Here, indeed, was a brilliant thought. The boys could track the bandits to their hiding-place, and possibly recover the ore. At least, they could return and report where the men had gone. There was a chance to distinguish themselves yet. In a moment they were mounted and dashing down along the track, toward the water tank.

Presently a shrill whistle was followed by the faint rumbling of the train as it resumed its way. "See?" yelled Whitey. "The train's just starting. We won't be very late, and the men's tracks will be plain. Gee! I hope it doesn't rain."

A few minutes' ride brought the boys to the deserted water tank. They dismounted to pick up the trail of the robbers. Near the tank, where the express car must have stood, were the traces of many feet. There were others leading from the cars in the rear. Noting these, Whitey said: "Mebbe they held up the passengers, too. It's likely that they would."

But, singularly enough, most of these tracks led on toward the high bridge which spanned the gully. The boys followed them curiously, and when they reached the bridge Injun stopped.

"Huh! Go back again, too," he muttered. And sure enough in the maze of footprints many seemed to lead back toward the water tank.

"Why do you s'pose they went to the bridge? Prob'ly to see if it was safe; that the robbers hadn't damaged it," Whitey said.

"Mebbe," said Injun, who was figuring things out in his own way and seldom spoke until he had them figured.

From the scramble of footprints near the tank, Injun picked out those of three pairs that diverged from the mass. Injun traced these back toward the gully. Two of the tracks were made by ordinary boots, the other by high-heeled cowboy boots. Whitey left this part of the chase entirely to Injun, and followed, leading the ponies.