The late Lord Kelvin was one of the most fascinating personalities in the learned world. He uttered with a delightful simplicity the thoughts, however romantic and fanciful, which bubbled up in his wonderful brain. It was because he was so much of a poet that he was so great a man of science. Atoms and molecules and vortices, and the vibrations and gyrations of ether, and “sorting demons” were all pictured in his mind’s eye, and used as counters of thought to give shape and the equivalent of tangible reality to his conceptions. By such conceptions he was able to present to himself and his listeners the complex mechanisms of crystals, of liquids, of gases, of electrical and magnetic currents, and the endless astounding proceedings of rays of light unsuspected by the ordinary man. I think the last occasion on which he spoke in public was after Sir David Gill’s brilliant address to the British Association at Leicester last August. Lord Kelvin was sitting close to me on that occasion, and I noticed that he never moved his gaze from the speaker. He followed Sir David’s account of stars, whose distance is stated by the number of years it takes for their light to travel to this earth, like an enraptured schoolboy, and cheered when the evidence for the existence of two great streams of movement of the heavenly bodies, in opposite directions, going no one knows whither, coming no one knows whence, was sketched to us by the lecturer. In proposing a vote of thanks to Sir David Gill, Lord Kelvin burst into a sort of rhapsody, in which, with unaffected enthusiasm, he declared that we had been taken on a journey far more wonderful than that of Aladdin on the enchanted carpet; we had been carried to the remotest stars and well-nigh round the universe, and brought back safely to Leicester on the wings of science, and the most marvellous thing about it all was that it is true!