As a first test of the existence of treasure in the lake, native divers explored some of the shallow places near the shore. A few ancient gold images were thus secured, enough to corroborate the legend regarding Guatavita. These images were curiously carved. One represented a small human figure seated in a sort of sedan chair. Another was a heart-shaped breastplate upon which were embossed human faces and various emblems. Others were statuettes, rude likenesses, probably, of those who threw them into the lake as votive offerings. These gold tokens spurred on the miners. Work on the tunnel was rushed, and a subterranean passage, several hundred feet in length, directed to a point just below the bottom of the lake, was soon completed. Then a peculiarly hard rock formation was reached that the boring machines could not pierce. To overcome it, dynamite was used. "Since dynamite was one of the final words in your test," said David, in telling his story to Leighton, "you know that its use in our venture brings the climax of my mining experience. How to explain this climax to you--or to myself--is beyond me. "When we decided to use dynamite in our excavations, a long fuse was laid from the tunnel's entrance to the unyielding wall at the other end. There this fuse was connected with a dynamite charge placed in the crevice of the rock to be destroyed. Raoul, waiting to set off the fuse, remained at the opening of the tunnel. I was at the further end, looking after the laying of the dynamite. As I started for the entrance, I was a little behind the others. The latter no sooner gained the outer air than a muffled roar shook the tunnel. The ground swayed, the terrific concussion of air seemed to rend my very brain, and I fell unconscious." David's story came abruptly to an end. Pale and listless, wearied by the effort to give a coherent account of his experiences, he looked hopelessly at Leighton. "Well," said the latter, "what then?" "If I could only tell you!" "Surely, you remember something--there is some clew----" "Nothing! Just--darkness." "Some faint flashes here and there--glimpses of people, scenes, a house, a street--the sound of voices, a word----?" "Nothing!" "Try to remember." "No use. I've tried it too often. It's all a blank. I thought, for an instant, that in your psychometer test the veil would be lifted. Instead--as you know--I went to pieces." "Very well," said Leighton reassuringly, "let us go back to your story. You were in the tunnel when the dynamite went off. You were thrown to the ground; you lost consciousness. What is the next step in memory?" "Wait," said David slowly. "The explosion was on the ninth of May. The date was indelibly fixed in my mind; I have verified it since. When I recovered consciousness----" "You mean, your normal consciousness," interjected Leighton. "Very well. When I came to myself, then, it was on the morning of the fifth of August."