But the gasp that escaped his lips at their sudden beauty was smothered in the sudden roar of deafening thunder that came from the cavern mouth far behind him.
He jerked to his feet. The air compression waves staggered him so that he tottered drunkenly for a moment and the sound battered his body. A flood of dust laden air flowed over him. Then gradually it settled about the chamber and there was only silence once more.
Nathan looked back at the box. A cleverly arranged switch had closed when he opened the lid, exploding the thunderous charge at the mouth of the cave. He struggled mentally with the problem of who had placed the explosive and the switch to seal the cave.
Perhaps Thymar had placed it as protection against robbery and his mind had been so affected by his wounds that he had forgotten it. Or someone might have planted it as a trap. But, if so, why were the Jewels left?
Almost forgetting that he was sealed in the cavern, he knelt down beside the box. The inner light of the Jewels pierced his eyes and seized his mind in a hypnotic trance. For an instant he thought he was gazing upon the beauties of some fair and alien world. In the red one there was a fantastic garden of Mars, but a Mars where no red sand clouds ever covered the cities with smothering death.
And in the green one he saw a fair and lovely vision of Earth so real it pierced him with nostalgia.
Then the visions faded. Whether he actually saw them or they were figments of imagination he never knew. But he had to shake his head and tear his sight away from the Jewels in order to pocket them.
Then, as he turned away, there broke upon the air a high-pitched song that trilled a moment's melody. It hung as if a crystal were suspended in the cavern, echoing its vibrations from chamber to chamber.
It came again. Nathan straightened and put out the light. He whipped out both flame lances.
It was the song of the Firebird.