What he made was a series of bamboo buckets, or cuplike sections of the hollow tube, with stones suspended inside to knock against the walls when the things were lightly shaken. These he intended to hang, one beside another, in a line from the brink of the wall, where a climber must strike them unawares and sound a resonant warning. But he found, on hanging a pair some ten feet down along the face, where the man had climbed in the night, that the wind would sway them to and fro against the rock and constantly ring their hollow tones. This defect he presently remedied by forming a frame, some ten feet long and one foot wide, in which all his cups were suspended, or moored, both top and bottom. They were thus so lightly hung that the smallest jar against the frame would joggle them all to musical utterance, while the wind could have no effect on any single one. The entire frame was lowered down till it rested a bit unevenly on two projecting shelves of rock, where it leaned a trifle outward like a picture on a wall, as the creepers that held it from falling were finally made secure. When Grenville, by way of a trial, nudged it once with a pole thrust down against it for the purpose, it rattled out a decisive alarm that one could have heard from the trail. Grenville thereupon brought out a bomb from his store and lowered it down below the frame, and six or eight feet to the side. This was secured not only by the fuse, but likewise by more of the creeper. Elaine, who during his absence had maintained the watch of the trail, now ran to the place, at Grenville's signal, for a moment's inspection of the whole arrangement and instruction concerning its use. It was while they were there that the haunting wail arose for a gasping spasm. It had practically failed. Sidney doubted if its loudest note could have been heard as far as the spring. But still the end of the tiresome day developed no attack. Grenville was completely puzzled by the tactics the boatmen had adopted. That they knew Elaine was present on the terrace there could be not a shadow of doubt. Even if the man she had thrust away from the cliff-edge fell to the sea and was dashed to pieces, or drowned, his friends who had brought him around to the place must have heard her voice and recognized its feminine quality. They would likewise know she could hardly be alone, and would guess her companions were not numerous or likely to be armed. No plundered wreckage lay about the shore from which castaways could have drawn ammunition or rifles. It was utterly impossible for any ignorant natives to imagine the loading of a cannon or the making of bombs from materials on the place.