“You and I, Percy,” he continued, “will see if we can’t improve this barrier, so that nobody can come in without making a noise. I think I know how it may be done. Come with me. Ulysses shall stay with you, Tom.”
As I took my station in the fort, the other two walked off down the gulley, and soon afterwards I heard above my head the sound of an axe; they were chopping wood up there for some reason or other. Presently Jack appeared upon the edge of the ravine, called out, “Look out, below!” and then, crash! came a small dead pine-tree to the bottom of the gully on the upper side of the bars. Two others followed, when Percy came down again, and having arranged the three trees so that they lay side by side, completely covering the whole width of the bed of the gorge, he looked up and shouted, “All right, Jack, send down the rest!” Down came three more trees, which were placed upon the top of the others, and the bars were then restored to their places. It was a great addition to our defences. The trees, arranged with their butts down-hill, presented a mass of brittle points to any intruder, and nobody could possibly climb over them or remove them without making a noise loud enough to arouse the sentinel if he should happen to be dozing; and as it was our intention that the sharp-eared Ulysses should always be a member of the guard, we were satisfied that now, at any rate, neither Squeaky nor anybody else could pass the bars without our permission.
This abatis being completed, Jack and Percy went off to arrange the camp, selecting a position in a bunch of trees a little to one side of the mouth of the gully, and soon after sunset Percy came up to relieve guard and to give me an opportunity to get my supper.
While I was thus engaged, Jack explained to me the course he proposed to follow, and the arrangement of the order of guard-mounting, of which he was to take his share at night; after which, leaving Percy and Ulysses to keep the first watch, he and I retired to bed.
Until all these preliminaries had been settled, Jack did not so much as mention the word “gold,” but next morning, soon after sunrise, while I took my place as sentinel for the day, he and Percy, who, as the finder of the nugget, naturally accompanied him to show him the place, went off together for the first day’s prospecting.
The stream, as I think I have mentioned, had cut for itself a little groove in the solid stone floor of the valley, while the floor itself, for a space of twenty feet on either side of the groove, had been laid bare by occasional freshets. Upon this level, smooth-swept surface stood the Mushroom Rock.
How it ever came there was a puzzle. It could not have rolled down the mountain, for, as Jack at once discovered, it was composed of two different kinds of stone, the lower being a sandstone, the upper a granite rock, and, of course, had it fallen from the mountain the pieces would have come apart in doing so. Jack’s solution of the problem appeared to be the only reasonable one. He said it must be one of those vagrant rocks known as “erratic boulders,” which had been carried here during the glacial period, and had been left standing when the ice melted away under it. That such a top-heavy rock should not have upset on the journey was hard to believe, but, in all probability, the stem had been originally as large in circumference as the cap—larger, perhaps—but being of softer material it had worn away in the course of ages more rapidly than the upper part.
Percy led the way to the spot where he had found his gold button, and pointed out to Jack the curious round hole in the bed of the stream from which it had come. There were several of these pot-holes, all of them, as it happened, down-stream from Mushroom Rock. They had been formed by the rattling around in them of a pebble, the hole ever growing larger and the pebble ever becoming smaller, until at last in the unequal contest the latter had been worn out entirely. Some of the holes were large enough to hold a bucketful of water; it must have taken hundreds of years and worn out hundreds of pebbles to make them.
Having inspected these pot-holes, and having found that each one of them had its little bed of black sand lying in the bottom, Jack said:
“Well, Percy, the first thing to be done is to gather as much as we can of this black sand and test it for gold. The greater part of the gold—if there is any—will be below the sand; so the holes must be scraped out perfectly clean.”