Of the six immortal modern scientists, three began life working as surveyors and civil engineers--Wallace, Tyndall, Spencer. From the number of eminent men, not forgetting Henry Thoreau, Leonardo da Vinci, Lincoln, Ulysses S. Grant, Washington--aye! nor old John Brown, who carried a Gunter's chain and manipulated the transit--we come to the conclusion that there must be something in the business of surveying that conduces to clear thinking and strong, independent action. If I had a boy who by nature and habit was given to futilities, I would apprentice him to a civil engineer. When two gangs of men begin a tunnel, working toward each other from different sides of a mountain, dreams, poetry, hypothesis and guesswork had better be omitted from the equation. Here is a case where metaphysics has no bearing. It is a condition that confronts them, not a theory. Theological explanations are assumptions built upon hypotheses, and your theologian always insists that you shall be dead before you can know. If a bridge breaks down or a fireproof building burns to ashes, no explanation on the part of the architect can explain away the miscalculation; but your theologian always evolves his own fog, into which he can withdraw at will, thus making escape easy. Darwin, Huxley, Spencer, Tyndall and Wallace all had the mathematical mind. Nothing but the truth would satisfy them. In school, you remember how we sometimes used to work on a mathematical problem for hours or days. Many would give it up. A few of the class would take the answer from the book, and in an extremity force the figures to give the proper result. Such students, it is needless to say, never gained the respect of either class or teacher--or themselves. They had the true theological instinct. But a few kept on until the problem was solved, or the fallacy of it had been discovered. In life's school such were the men just named, and the distinguishing feature of their lives was that they were students and learners to the last. Of this group of scientific workers, Alfred Russel Wallace alone survives, aged eighty-nine at this writing, still studying, earnestly intent upon one of Nature's secrets that four of his great colleagues years ago labeled "Unknown," and the other two marked "Unknowable." To some it is an anomaly and contradiction that a lover of science, exact, cautious, intent on certitude, should accept a belief in personal immortality. Still, to others this is regarded as positive proof of his superior insight.