The extraordinary powers of calculation entirely from memory are very surprising. The mathematician Wallis, in bed, and in the dark, extracted the cube root from a number consisting of thirty figures. George III. had a memory remarkably retentive. He is said never to have forgotten the face he had once seen, or the name once heard. Carolan's memory was remarkably quick and retentive. On one occasion, he met a celebrated musician at the house of an Irish nobleman. He challenged him to a trial of musical skill. The musician played the fifth Concerto of Vivaldi on his violin, to which Carolan, who had never heard it, listened with deep attention. When it was finished, he took his harp, and played the Concerto from beginning to end, without missing a single note. An instance of great memory is related of La Motte, who was invited by Voltaire, then a young man, to hear a tragedy which he had just finished. La Motte listened with great attention, and was delighted with it. However, he said he had one fault to find with it. On being urged by Voltaire to say what _that_ was, he replied, that he regretted that any part of it should have been borrowed. Voltaire, chagrined and incredulous, requested that he would point this out. He named the second scene of the fourth act, saying, that, when he had met with it, it had struck him so much, that he took the trouble of transmitting it to memory. He then recited the scene, just as Voltaire had read it, with the animation which showed how much it pleased him. Voltaire, utterly confounded, remained silent; the friends who were present looked at each other in amazement; a few moments of embarrassment and dismay ensued. La Motte at length broke the silence: "Make yourself easy, sir," said he, "the scene belongs to no one but you. I was so charmed by its beauty that I could not resist the temptation of committing it to memory."