The planets also lend interpretation to this principle. Years ago our nation sent astronomers to Africa to witness the transit of Venus. Preparations began months beforehand. A ship was fitted up, instruments packed, the ocean crossed, a site selected and the telescopes mounted. Scientists made all things ready for that opportune time when the sun and Venus and earth should all be in line. That critical moment was very brief. Instinctively each astronomer knew that his eye must be at the small end of the glass when the planet went scudding by the large end. Once the period of conjunction had passed no machinery would offer itself for turning the planet back upon her axis. Not for astronomers only are the opportune times brief. For all men alike, failure is blindness to the strategic element in events; success is readiness for instant action when the opportune moment arrives. When nature has fully ripened an opportunity man must stretch out his hand and pluck it. Inventions may be defined as great minds detecting the strategic moment in nature; Galileo finding a lens in the ox's eye; Watt witnessing steam lift an iron lid; Columbus observing an unknown wood drifting upon the shore. To untold multitudes nature offered these opportune moments for discovery, but only Galileo, Watt and Columbus were ready to seize them. As for the rest, this is our only answer to nature: "While thy servant was busy here and there, the strategic moment was gone." This majestic principle often appears in history. There is a strategy in Providence. Nations, like individuals, have their crisis hours. Through events God makes all society plastic, and then raises up some great man to stamp his image and superscription upon the nation's hot and glowing heart. As scholars move back along the pathway of history, they discern in each great epoch these strategic conditions. How opportune the moment when Jesus Christ appeared! Alexander's march had scattered every whither the seeds of learning; the Greek language had turned the whole world into one great whispering gallery, in which the nations were assembled; all the provinces around the Mediterranean were linked together by the newly completed system of roads; the Roman judge was in every town to set forth the rights of citizens of the empire; the Roman soldier was there to protect all who brought messages of peace; the long-expected hour had struck. Then Christianity set forth from Bethlehem upon its errand of love. Along every highway ran the eager feet of the messengers of peace and good-will. Events were fully ripe, and soon Christianity was upon the throne of the Caesars.