Meyer was sounding the floor with a staff of wood--an operation which he had only just began after the walls proved barren.
"Listen now," he said, letting the heavy staff drop a few paces to the right of the altar, where it produced the hard, metallic clang that comes from solid stone when struck. Then he moved to the front of the altar and dropped it again, but now the note was hollow and reverberant. Again and again he repeated the experiment, till they had exactly mapped out where the solid rock ended and that which seemed to be hollow began--a space of about eight feet square.
"We've got it," he said triumphantly. "That's the entrance to the place where the gold is," and the others were inclined to agree with him.
Now it remained to put their theory to the proof--a task of no small difficulty. Indeed, it took them three days of hard, continual work. It will be remembered that the floor of the cave was cemented over, and first of all this cement, which proved to be of excellent quality, being largely composed of powdered granite, must be broken up. By the help of a steel crowbar, which they had brought with them in the waggon, at length that part of their task was completed, revealing the rock beneath. By this time Benita was confident that, whatever might lie below, it was not the treasure, since it was evident that the poor, dying Portuguese would not have had the time or the strength to cement it over. When she told the others so, however, Meyer, convinced that he was on the right tack, answered that doubtless it was done by the Makalanga after the Portuguese days, as it was well known that they retained a knowledge of the building arts of their forefathers until quite a recent period, when the Matabele began to kill them out.
When at length the cement was cleared away and the area swept, they discovered--for there ran the line of it--that here a great stone was set into the floor; it must have weighed several tons. As it was set in cement, however, to lift it, even if they had the strength to work the necessary levers, proved quite impossible. There remained only one thing to be done--to cut a way through. When they had worked at this task for several hours, and only succeeded in making a hole six inches deep, Mr. Clifford, whose old bones ached and whose hands were very sore, suggested that perhaps they might break it up with gunpowder. Accordingly, a pound flask of that explosive was poured into the hole, which they closed over with wet clay and a heavy rock, leaving a quill through which ran an extemporized fuse of cotton wick. All being prepared, their fuse was lit, and they left the cave and waited.