There are many wonderful things to be learned about the stars, to which I hope you will give your earnest attention as you have the opportunity. Among the rest is this fact, that some stars have ceased to be visible to us. Tycho Brahé said that on one occasion he found a number of villagers looking up at the sky; and on asking them why they were gazing at the heavens, they told him that a new star had suddenly appeared. It shone brightly for a few months, and then vanished. Many times a starry world has seemed to turn red, as if it were on fire; it has apparently burned, and blazed away, and then disappeared. Kepler, writing concerning such a phenomenon, says: "What it may portend is hard to determine; and thus much only is certain, that it comes to tell mankind either nothing at all, or high and weighty news, quite beyond human sense and understanding." In allusion to the opinions of some, who explained the novel object by the Epicurean doctrine of a fortuitous combination of atoms, he remarks, with characteristic oddity, yet good sense, "I will tell these disputants--my opponents--not my opinion, but my wife's. Yesterday, when weary with writing, and my mind quite dusty with considering these atoms, I was called to supper, and a salad that I had asked for was set before me. 'It seems, then,' said I aloud, 'that if pewter dishes, leaves of lettuce, grains of salt, drops of water, vinegar, and oil, and slices of egg, had been flying about in the air from all eternity, it might at last happen, by chance, that there would come a salad.' 'Yes,' says my wife, 'but not one so nice or well dressed as this which I have made for you.'" So I should think; and if the fortuitous combination of atoms could not make a salad, it is not very likely that they could make a world. I once asked a man who said that the world was a fortuitous concourse of atoms, "Have you ever chanced to have no money, and to be away where you knew nobody who would give you a dinner?" He replied, "Yes, I have." "Well, then," said I, "did it ever happen to you that a fortuitous concourse of atoms made a leg of mutton for you, with some nice boiled turnips, and caper sauce, for your dinner?" "No," he said, "it has not." "Well," I answered, "a leg of mutton, at any rate, even with turnips and caper sauce included, is an easier thing to make than one of these worlds, like Jupiter or Venus."