THOMAS ALVA EDISON 407 natural attraction of any kind, unless it be what to Edison indeed is a great charm an uninterrupted view of the sky ; a place virtually unknown before he planted there the rude buildings that house his wonderful inventions ; yet now a place known to scientific men all over the world ; the Mecca of many a mind seeking to wrest from Nature her dearest secrets. No doubt, many of the inventions that have made Edison famous must be ascribed in their conception and ripening to various periods of his life, but to the popular mind they are all associated with the wizard's present home, from whence for several years the bulletins of inventions playful, useful, necessary, revolution- ary often as simple in their mechanism as they are astonishing in their results, have been given to a delighted world. Some of Edison's inventions have a char- acter at present of little more than picturesque playfulness, such as the Phono- graph, perhaps the most remarkable of these minor inventions ; the Aerophone, by which sounds are amplified without loss of distinctness ; the Megaphone, an instrument which, inserted in the ear, so magnifies sounds that faint whispers may be heard a thousand feet ; the Phonometer, for measuring the force of the sound- waves caused by the human voice; the Microtasimeter, for measuring small varia- tions in temperature. This has been tested for so small a variation as 24 ^ 00 of a degree Fahrenheit, and in 1878 was used to detect the presence of heat in the sun's corona. The most familiar of these lesser inventions is the Phonograph, by which sounds are made self-recording and capable of being repeated. While this curious invention almost childish in its simplicity is as yet little more than a plaything, and has proved of small utility, it makes, nevertheless, a strong appeal to the imagination when we reflect that by its aid the voice of any human being may be transmitted to ages far in the future, and its living tones be heard long after he who uttered them has returned to the dust. But, while these inventions have the charm that invests " the fairy-tales of sci- ence," the world-wide fame of Edison rests upon greater gifts to the world ; the various improvements he has made in the telegraph, and the perfection to which he has brought the electric light. The invention of the telephone, by which per- sons are enabled to converse with one another at very long distances, and by which concerts, operas, and orations or sermons in one city can be heard by an audience assembled in another, is one of the most remarkable of Edison's achieve- ments, and one the usefulness of which in various directions it is easy to foresee. The idea of the transmission of messages in opposite directions by the same wire was one that had early occurred to Edison, but he was long in reducing it to prac- tice. The secret once discovered, however, he rapidly progressed until he had brought out the sextuple telegraph, where we believe the ability of the instru- ment rests at present. The inventor next turned his mind to the study of the electric lamp, in which he saw great possibilities. He believed that he could produce a light that should be cheaper than gas, and also purer, more steady, and more to be depended on. He rejected the principle of the Voltaic arc involved in the Brush patent then in use, by which the electric current was passed through a strip of platinum or other
