"Oh, that was merely a powerful magnet that attracts gold instead of iron," explained Sajipona, as if such trifling matters were scarcely worthy to be ranked with the other marvels of the cave. "This magnet played a great part, centuries ago, in gathering together all the wealth of my ancestors from the Sacred Lake where it had been cast during the Feast of the Gilded Man. To-day it is never used because all the gold has been taken out of the lake. But--was there nothing else mysterious?" "Caramba!" ejaculated Miranda, "I know! When we come in from the outside, all is open; we can come in and we can come out. And then, this little old woman is frighten, and I take her out. That is, I think I take her out. But the wall is shut, and we cannot see where it is. We are in prison. Who did that? There is no one there." Sajipona laughed. "Yes, that is it! No one was there--except Radium, the influence from the great globe hanging above us. Here, you see, it does many more things than it does in your outside world. It is really the eye of the cave--and sometimes the arm. Although its light does not, as you know, extend into the outer cave, it reflects here, within this circle, whatever is lighted up beyond there. When you came in with your torches I was able to follow you by this means--very obscurely, of course, because torches throw only a small circle of light. I could hardly make you out, but I felt sure who you were. I was expecting you. And then, because I needed you here and feared you might grow tired of so long a journey, I shut the entrance to the cave so you could not escape. That is where radium works like an arm. It can carry an electric force, an irresistible current, without using wire. For our own safety we have this force connected with the entrance to the cave. When that entrance is open and we want to close it, this force is released and moves a great rock that glides into place across the passageway, where it seems to be a part of the wall on either side."