"First-class," Carstairs answered.
"What did you think of while I was playing?"
"What I want to do. As a matter of fact I elucidated a knotty point in connection with an idea I'm working out."
Darwen's dark eyes lighted up into a positive gleam. "It's curious," he said. "I bet when old Chopin composed that thing he had no ideas of electrical machinery in his head. What's the line of the invention?" He swung round and toyed with the keys; a low, sweet strain welled out, pleading, winning.
"Well, it occurred to me one day that there was no adequate reason why—" Carstairs stopped, seemingly interrupted by his own thoughts. "No," he said, as if speaking to himself. "It's not quite right after all." He laughed aloud suddenly. "The reasons," he said in his normal voice, "appear more and more adequate as I investigate the case, still——"
Darwen waited in expectation for some time, but Carstairs remained silent, lost in thought. Suddenly Darwen burst into life and rolled out an immense volume of sound from the piano.
A look of pain crossed Carstairs' features. "What the devil do you make that row for?"
"That row, as you call it, is from Wagner's 'Lohengrin.'"
"Is that so? Well, it's a jolly good imitation of a breakdown in the engine room."
Darwen laughed. "You have a vulgar mind, old chap." He branched off into an Hungarian waltz.