The volume before me thus speaks of the two methods of finding a planet, the one worker using the most powerful telescope, and the other making mathematical calculations: "To detect a planet by the eye, or to track it to its place by the mind, are acts as incommensurable as those of muscular and intellectual power. Recumbent on his easy-chair, the practical astronomer has but to look through the cleft in his revolving cupola in order to trace the pilgrim star in its course; or, by the application of magnifying power, to expand its tiny disk, and thus transfer it from among its sidereal companions to the planetary domains. The physical astronomer, on the contrary, has no such auxiliaries: he calculates at noon, when the stars disappear under a meridian sun; he computes at midnight, when clouds and darkness shroud the heavens; and from within that cerebral dome which has no opening heavenward, and no instrument but the eye of reason, he sees in the disturbing agencies of an unseen planet, upon a planet by him equally unseen, the existence of the disturbing agent, and from the nature and amount of its action he computes its magnitude and indicates its place." What a grand thing is reason! Far above the mere senses, and then faith is high above reason; only, in the case of the mathematical astronomer of whom we are thinking, reason was a kind of faith. He argued: "God's laws are so-and-so and so-and-so. This planet Uranus is being disturbed, some other planet must have disturbed it, so I will search and find out where he is;" and when his intricate calculations were completed, he put his finger on Neptune as readily as a detective lays his hand on a burglar, and a great deal sooner; indeed, it seems to me that it is often easier to find a star than to catch a thief. Neptune had long been shining before he was discovered and named; and you and I, brethren, may remain unknown for years, and possibly the world may never discover us; but I trust that our influence, like that of Neptune, will be felt and recognized, whether we are seen of men or only shine in solitary splendor to the glory of God. * * * * * Well, we have traveled in thought as far as Neptune, which is about 2,748,000,000 miles from the sun; and, standing there, we look over into space, and there are myriads, and myriads, and myriads of miles in which there appear to be no more planets belonging to the solar system. There may be others that have not been discovered yet; but, as far as we know, beyond Neptune there is a great gulf fixed.