Barney cleard his throat. "Uh, the idea is," he said, "that a first-rank mathematician would go on learning, improving, gaining knowledge and power we can't guess at, after passing on. We want a man who pioneered in non-Euclidean geometry."

"Riemann is considered definitive," Falkenberg told us, "but he did build on the work of others, like Hamilton, and had successors of his own. We don't know how far the incomparable Gauss went, since he published only a fraction of his thought. On the whole, I'd favor Lobachevsky. He was the first to prove a geometry can be self-consistent that denies the axiom of parallels. Around 1830 or 1840 as I recall, though the history of mathematics isn't my long suit. Everything in that branch of it stems from him."

"That'll do," Barney decided, " considering we don't know if we can get any particular soul for an ally. Any whatsoever, for that matter," he added raggedly. To Falkenberg: "You and the pastor work out the words while we establish the spell."

...

"Hear us, O God, from Heaven Thy dwelling place," he called. "Thou knowest our desire; make it pure, we pray Thee. In Thy sight stand this man Steven and this woman Virginia who are prepared to harrow hell as best as is granted them to do, that they may confound Thine enemies and rescue an unstained child from the dungeons of the work. ...We beg Thee to allow them a guide and counselor...If we are not worthy of an angel, we ask that Thou commend them unto Thy departed servant Nikolai Ivanovitch Lobachevsky, or whomever else may be knowledgeable in these matters as having been on earth a discoverer of them."