As the lad spoke Frank and Jack broke into growls which might well have come from the throat of the grizzliest grizzly in the Rocky Mountains, while Pat sent forth a wolf howl, which might well have been a signal to the pack.
“You may meet the real thing out here,” warned Ned, turning back to look over the plateau, now shining in the light of a half-moon. “There are both bears and wolves in this region. When you meet them, don’t wait for Boy Scout signs!”
“Oh, we’ll initiate ’em, all right,” Jimmie called from the tent, and Ned and Frank moved on down the declivity toward the lake.
It was still early evening, and the moon was low down in the east, so the valley where the lake lay was not touched by its light. Indeed, the plateau where the boys were would have been in the shadow of the mountain only for the dropping of the shoulder of the divide.
In half an hour the two boys, after several slides which were anything but pleasant, gained the beach. The campfire was now dead, and the locality was still save for the voice of a night bird and the occasional splash of a leaping fish. The mouth of the cavern loomed like a dark patch on the lower bulk of the mountain.
Making as little noise as possible, Ned and Frank crept into the cavern, advancing by the sense of feeling until they came to the very end before turning on one of the electric flashlights. The round eye of the flame showed a long, narrow, tunnel-like tube running directly east, under the mountain. The door of rock was as the boys had left it earlier in the day.
Ned examined that portion of the rock which had swung out into the first chamber with considerable care, as the story of the swinging stone had interested him greatly. All along the top, up to the center, he found the checks of a stone-chisel. Exactly in the middle an elevation of an inch fitted into a round cavity in the upper rock. At the bottom the same conditions were discovered.
“Rather a clever job,” Ned said, “but I don’t see how it was ever done.”
“This door,” Frank said, “is not exactly like the remainder of the wall in grain, so it must have been brought here from some other locality. Of course there was a hole between these two chambers, or the second one would never have been found. It would be easy enough to fit the stone door in by grooving out from the lower cavity and sliding the under pivot in.”
“Sure,” Ned replied, getting down to examine the lower part of the door more closely, “and that is just what was done. Then the groove was filled with concrete. Pretty classy work here!”