In the same year of 1877, Edison made his great invention, the carbon telephone transmitter, which increased enormously the effect of the voice in varying the resistance of a telephone circuit, and thereby increased the loudness of telephone speech. In the same year, Berliner invented the induction transmitter, which consisted of a primary coil of small resistance in circuit with the transmitter and the secondary coil connected to the outside circuit. These two inventions, added to Bell's original invention, made the telephone of today--in its essential features. In 1878, Edison produced his incandescent lamp, in which a carbon filament, enclosed in a bulb exhausted of air, was heated to incandescence by an electric current. The importance of this invention need hardly be even mentioned. As to the originality of the conception, there are many opinions; for several experimenters had been working in this field, and many brilliant results had been achieved. Important as this invention was, we can imagine the Machine to exist without it, though not in quite so perfect and complete a form. Its main use is its obvious use; though there can be no doubt that the improvement it wrought in the conditions of comfortable living, and the attractions it offered to ambitious youths enlisted a large army in the study of the physical sciences, gave impetus to all the mechanic arts, and assisted in many important ways the upbuilding of the Machine. In 1879, Appleby invented the automatic grain-binder, and Sir William Crookes made his epochal discovery of cathode rays. This discovery, like many others of a highly scientific character, was not of immediate practical value; consisting as it did in the fact that if the poles of the secondary circuit of a Rhumkorff coil were connected to the two ends of a glass tube from which nearly all the air (or other gas) had been exhausted, a stream of electrified particles was projected from the cathode, or negative pole. These particles were evidently projected with great violence; for if they struck the side of the tube, they produced a brilliant illumination there; while if they struck a piece of metal they developed heat. If the metal were sufficiently thin, it was melted. Later study of these cathode rays developed the fact that the stream of charged particles could be deflected by magnetic and electric fields, thus showing that they had actual physical mass; and still later studies resulted in that mass being determined, and also the amount of the electric charges on them. To an individual particle the name electron was given; and the interesting fact developed that the mass of an electron is only about one-thousandth that of an atom of hydrogen.