"A lamp of electricity," he said. "How have you managed to keep it hidden for all these centuries! After all these years of trying to arrive at a theory of-" He choked slightly, and seemed to be fighting for self-control, as if he had been the victim of a monstrous practical joke. "Why have you hidden it? Is there some religious significance- And what-" Complete confusion stopped him. He shook his head and looked around as if for an escape.