to open them when you get the bacon fried to a crisp. I see our finish if you got one of the bean cans opened. Say, but I could eat a peak off the divide!”

“Well, the divide is up there, all right,” Pat grinned, “go on up and take a bite off it. On this side that ridge away up there the rivers run into the Pacific ocean. On the other side they run into the Atlantic ocean. Split a drop when you get on top and send your best wishes to both oceans. And don’t you remain away too long, either, for this bacon is going to be cooked in record-breaking time.”

Leaving Pat to prepare the supper, Frank and Jack turned their faces upward toward the main divide of the Rocky Mountains, 4,000 feet above their heads. It was a splendid scene, and they enjoyed it to the full. To the north the green forests of British Columbia stood crinkling under the almost direct rays of the August sun, to the east, almost over their heads, stood the backbone of the continent of North America, to the south stretched the broken land of Montana, while to the west lay the valleys and ridges of Idaho, Montana, and Washington beyond which pulsed the mighty swells of the Pacific.

Immediately to the north of the position occupied by the camp, and within a mile of the international boundary line, Kintla lake lay like a mirror in the lap of the mountains, reflecting peaks and silent groves in its clear waters. From the lake, ten miles in length by half that in width, an outlet flowed westward into the North Branch of the Flathead river.

The level plateau where the camp had been pitched was not far from two acres in extent, with the bulk of the mountain to the east, a drop of a thousand feet to the south, and steep but negotiable inclines to the west and north. The lake was 300 feet below the level of the plateau, which was about 3,000 feet above the sea level and 4,000 feet below the summit of the divide at that point in the long range of mountains.

There were peaks to the north and south which showed eternal snow and ice, but there was a lowering of the shoulder of the great chain directly to the east, so there was no snow in sight there. There were forest trees low down in the cañon to the south, and on the slopes to the west and north, but the plateau and the sharp rise toward the summit were bare.

While Pat sliced his bacon and mixed corn-meal, soda, salt and water to make hoecakes, to be fried in bacon grease, Frank and Jack wormed their way up the face of the mountain, toward a shelf of rock some hundred feet above the plateau. It was hard climbing, but the lads persisted, and soon gained the elevation they sought, from which it was hoped to gain a fine view of the country toward Missoula.

“Good thing we don’t want to go any farther,” Frank exclaimed, throwing himself down on the ledge and wiping his streaming face. “We couldn’t scale the wall ahead with a ladder. Now,” he went on, “look out there to the south and see if there’s an aeroplane in sight.”

Jack brought out the field-glass and looked long and anxiously, but there was no sign of a man-made bird in the clear sky.

“I don’t believe, after all, that he’ll come in an aeroplane,” the boy said, directly. “Suppose he took a notion to get a motor boat and run up the north branch of the Flathead river, and so on into Kintla lake, down there? How long would it take him to make the trip?”

“About ten thousand years,” was Frank’s reply. “He never could get up the north branch. There’s too many waterfalls. Why, man, the stream descends several thousand feet before it gets to sea level.”

“Anyway,” Jack replied, “if you’ll get out of my way I’ll take a look at the lake through the glass.”

“You’ll probably see him come sailing up the slope in a battleship,” Frank said, in a sarcastic tone.

Jack, without speaking, turned his glass to the north and gazed long and anxiously over the lake. Presently Frank saw him give a start of surprise and lean forward, as if to get a closer view of some object which had come into the field of the lens.

“What is it?” he asked.

Jack passed him the glass with no word of explanation, and the boy hastily swept the shores of the mountain lake.

“I don’t see any motor boat,” he said, directly.

“Well, what do you see?” Jack asked, expectantly.

“For one thing,” Frank replied, “the smoke of a campfire.”

“I saw that, too,” Jack said, “and didn’t know what to make of it. Also, I saw a rowboat sneaking around that green point to the east.”

“That is what is puzzling me,” Frank replied. “Years ago there was a Blackfoot reservation just over the divide, and a Flathead Indian reservation down by Flathead lake, to the south, but I had no idea the Indians were still about. Still, the people you saw were probably Indians. Suppose we go down there and look the matter up. We’ve got to have some sort of a yarn to tell Pat when we get back to camp.”

The two boys scrambled down almost vertical surfaces, edged along narrow ledges, slid down easier inclines, and finally came to the rim of beach about the lake. There, at the eastern end of the pretty body of water, they came upon the still glowing embers of a fire.

Close to the spot where the remains of the fire glimmered in the hot air, they saw the mouth of a cavern which seemed to tunnel under the body of the mountain to the east. There were numerous tracks about the fire, and some of them led to the entrance to the cavern.

“Whoever built this fire,” Jack exclaimed, “wore big shoes, so it wasn’t Indians. No, wait!” he added, in a moment, “there are tracks here which show no heel marks. What do you make of that?”

“Must be moccasins,” Frank said. “The Indians may still be in the woods about here.”

“I’m going into the cavern to see what’s stirring there,” Jack said, “and before I go I’ll have a look at my artillery.”

The boy looked his revolver over, and before Frank could utter a warning, he darted away into the gloom of the cave. Frank did not follow him, but turned in the direction of the point where the boat had disappeared.

A dozen yards on his way he stopped and listened. A voice, sounding like that of a person in a deep well, reached his ears, and he turned back.

He gained the mouth of the cavern in half a minute and plunged inside. It was dark a dozen feet from the entrance, but he struck a match and moved on, finally coming to a smooth wall which appeared to shut off farther progress.

When he turned about and faced the opening every object between where he stood and the mouth stood revealed against the bright sunshine outside. There were a few loose rocks, a rude bench, a small goods box, and nothing else. Jack was nowhere in eight.

He examined the walls of the cavern but discovered no lateral passages. He called out to his chum, but received no response. Where was Jack? If he had left the cavern he would have been seen. It was a perplexing mystery, and the boy sat down on the box and listened for a repetition of the sounds he had heard.

For a moment no sounds came, then a voice, seemingly coming out of the solid wall behind him reached his ears. He could distinguish no words for a time, and then it seemed that he was being called by name.

He called to Jack again and again, but received no answer. Jack was evidently there somewhere, but where? The smooth walls gave no indication of any hidden openings, and there was in view no crevice through which a voice behind the walls might penetrate. It seemed either a silly joke or an impenetrable mystery.