=A.D. 1684.=--Hooke (Dr. Robert), English natural philosopher (1635–1703), who, in 1677, had succeeded Oldenburg as Secretary to the Royal Society, gives the earliest well-defined plan of telegraphic transmission, in a paper addressed to the Royal Society “showing a way how to communicate one’s mind at great distances ... 40, 100, 120, etc., miles ... in as short a time almost as a man could write what he would have sent.” His apparatus consisted of an elevated framework supporting an open screen, behind which were suspended as many wooden devices, or symbols, such as circles, squares, triangles, etc., as there were letters in the alphabet. In the daytime these devices were drawn up by a rope behind the screen and made visible in the open space, while during the night use was made of torches, lanterns or lights. Hooke also showed, in 1684, that iron and steel rods can be permanently magnetized by strongly heating them and by rapidly cooling them in the magnetic meridian (“Enc. Brit.” 1857, Vol. XIV. p. 3). But, what is still more singular, he had, even previous to the above-named date (_i. e._ in 1667), alluded to the possibility of telephoning, that is, communicating sound through a wire. He thus expresses himself: “And as glasses have highly promoted our seeing, so it is not improbable that there may be found many mechanical inventions to improve our other senses--of hearing, smelling, tasting, touching.... ’Tis not impossible to hear a whisper a furlong’s distance, it having been already done; and perhaps the nature of the thing would not make it more impossible though that furlong should be ten times multiplied. And though some famous authors have affirmed it impossible to hear through the thinnest plates of Muscovy glass, I know a way by which it is easy to hear one speak through a wall a yard thick. It has not been examined how far acoustics may be improved, nor what other ways there may be of quickening our hearing, or conveying sound through other bodies than the air, for that is not the only medium. I can assure the reader that I have, by the help of a distended wire, propagated the sound to a very considerable distance in an instant, or with as seemingly quick a motion as that of light, at least, incomparably swifter than that which at the same time was propagated through the air; and this not only in a straight line, or direct, but in one bended in many angles.”