Great sorrow is often needed to develop a good teacher. When the oil wells in Pennsylvania dry up, the owners sink great torpedoes of nitro-glycerine down into them, a thousand or fifteen hundred feet to the bottom, and there explode them, rending and crushing the rock on every side, not infrequently opening pent-up fountains of oil, which change the worthless hole into a richly producing well again. So the Christian teacher sometimes seems to dry up. Though a fountain of truth may be hidden in his heart, it is of no value until it is broken open by some sharp providence, until God lets down into that heart some great sorrow, crushing it and setting free the richness of his truth and goodness. Then with what fullness, tenderness, persuasiveness and power does the Christian teacher give forth the truth to his scholars! —Sel.