eye, for one thing, would suggest that light may be in the nature of a vibration. Scores of other lines of study in a similar manner have at length brought all who pursue them to the conclusion that light is a form of vibration. Robert Hooke in England (1631-1703) and Christian Huygens in Holland (1629-1695), back in the seventeenth century seem to have been the first to give expression to this idea, which was nothing more than an inkling in Hooke's mind, but which was the necessary result of observations on the part of Huygens. For nearly a century the idea lay dormant, largely because Sir Isaac Newton (1642-1727), the cleverest thinker of his time, opposed it. It was perhaps unfortunate for the success of the theory that Huygens, its founder, adopted the word ether, for that was an old term, and had been very badly overworked. The word ether, or æther as it was often written, had been invented in the days of ignorance, for such foolish reasons as: (a) because "nature abhors a vacuum," or (b) "for planets to swim in," or (c) "to constitute electric atmospheres and magnetic effluvia," or (d) "to convey sensations from one part of our bodies to another." "When we remember," says Maxwell, "the mischievous influence on science which hypotheses about æthers used formerly to exercise, we can appreciate the horror of æthers which sober-minded men had during the eighteenth century." Newton in England (1642-1727) and Laplace in France (1749-1827) stoutly opposed the undulatory theory of Huygens and championed a corpuscular or emission theory, that light-giving and heat-giving bodies emit a subtile fluid. There is no other instance in the whole history of modern physics in which truth was so long kept down by authority. Fresnel (1788-1827) and Arago (1786-1853) in France appear to be the only persons during the eighteenth century who caught a clear vision of the truth of the undulatory theory. But it remained for Mr. Thomas Young (1773-1829), a colleague of Sir Humphrey Davy at the Royal Institution, in his Bakerian lecture (1801) on "Theory of Light and Colour" to bring together such good evidence for the ether wave theory that it has hardly been questioned since. Young, like Davy, was a most remarkable man in literature and in science. It was he who first deciphered the Rosetta Stone, now in the British Museum, and gave us a key to the Egyptian hieroglyphics. Probably he was the only man who was able to overthrow the influence of Newton's authority even a century after Newton did his work. Faraday's (1791-1867) chief work as director of the laboratory of the Royal Institution, London, was a study of ether phenomena, particularly electric and magnetic. About seventy-five years ago he became impressed with the fact that although wires may give direction to an electric current the electric influence is not confined to the wires, but may permeate more or less widely the region about them.