Page:Collier's New Encyclopedia v. 09.djvu/335

LEFT TELEPATHY 283 TELEPHONE fully made by competent persons that sensations, ideas, information and men- tal pictures can be transferred from one mind to the other without the aid of speech, sight, hearing, touch or any of the ordinary methods by communicating such impressions or information. Some persons can voluntarily project the mind or some independent mental activity a distance of 100 or 1,000 miles so that it can make itself known and recognized, perform acts and even carry on a con- versation with the person to whom it is sent. Scientific work on thought transfer- ence began systematically in England in 1882, when the Society for Psychical Re- search was founded under the presidency of Professor Sidgwick of Cambridge. Professor Crookes has outlined a theory according to which thought transference is effected by inconceivably minute and rapid ether waves. After pointing out that vibrations of ether of a certain rapidity produce light, he says that there are higher rates of vibrations which are utterly imperceptible to our senses and it is not inconceivable that intense thought, concentrated toward a sensitive being with whom the thinker is in close sympathy, may induce a telepathic chain along which brain waves can go straight to their goal without loss of energy due to distance. TELEPHONE, an instrument for transmitting sounds or speech to distances where such would be inaudible through aerial sound waves. This definition ex- cludes speaking tubes, which act simply by preserving and concentrating sound waves. Telephonic action depends on the fact that sound waves in air are capable of communicating vibrations to a stretched membrane, and if by any means such vibrations can be transmitted with true resemblance to another mem- brane at any distance, such receiving membrane will reproduce the sound. This capacity of a single vibrating membrane to reproduce the most complicated sounds, as of speech, is in reality the greatest mystery connected with the mat- ter; all else relates to the mechanism of transmission only. The essential na- ture of the operation is well shown in the common toy telephone sold in the streets, in which the floors of two small tin cups consist of stretched membranes, or even of paper. The two membranes are con- nected by a long piece of twine. If now one cup be held to the mouth and spoken into, the voice communicates vibrations to the membrane. The stretched twine communicates similar vibrations to the membrane of the other cup, and if its cavity be held to the ear the sounds will be heard. This is the true mechanical telephone. The term is more commonly applied to the electrical telephonic ap- paratus so much used in modern life, but the principle is precisely similar. Such apparatus generally belongs to one of two main classes. The true inventor of the first telephone Avas undoubtedly Philip Reis, who showed, in 1861, that variations in an electric cur- rent caused by a vibrating membrane could reproduce the necessary vibrations. Reis in this way transmitted musical sounds and even words; but his ap- paratus was imperfect, and it was re- served for Alexander Graham Bell to per- fect that which is still commonly used and known as the Bell telephone, though it is the nearly unanimous opinion o£ electricians that Bell's patent has been held by courts of law to cover far more ground than is really due to him, much to the public detriment and to the hin- drance of progress. In Bell's telephone there is a cylindrical steel magnet, sur- rounded at one end by a coil of wire,whose ends are connected by wire with the cir- cuit or line wire. It will now be under- stood that any change in the power of the magnet will cause currents in this wire. Near, but not touching, the magnet's end is stretched a very thin sheet of iron, as a membrane, which is spoken to through the mouthpiece. Thus made to vibrate, the iron membrane approaches to and recedes from the magnet; and as it acts toward this as an armature, tending to close the magnetic circuit, the effect is to produce fluctuating degrees of free magnetism, which again produce fluctu- ating or undulating currents in the line wire. But if these fluctuating currents are received in a precisely similar instru- ment, they in its coil produce variable magnetic force in the magnet, and this reproduces vibrations in the second iron membrane, which reproduce the sound. The second class of instruments are based on the microphone. If part of a galvanic current is composed of two or three pieces of matter (preferably charcoal) in loose contact, variations in the current produce variations in the con- tact pressure of the loose pieces, and the converse. Hence, instead of a vibrating membrane causing undulating currents by means of a magnet as in the Bell method, it may abut against such a series of mere contacts, and thus cause an un- dulating or variable current, which again is capable of converse action. A micro- phone is thus capable, with more or less modification, of being used as a tele- phone, and the employment of either method is a question of practical con- ditions. The Bell telephone is indepen- dent of any battery, being self-acting;