Bell's patent of 1876 was of an all-embracing character, which only the make-and-break principle, if practical, could have escaped. It was pointed out in the patent that Bell discovered the great principle that electrical undulations induced by the vibrations of a current produced by sound-waves can be represented graphically by the same sinusoidal curve that expresses the original sound vibrations themselves; or, in other words, that a curve representing sound vibrations will correspond precisely to a curve representing electric impulses produced or generated by those identical sound vibrations--as, for example, when the latter impinge upon a diaphragm acting as an armature of an electromagnet, and which by movement to and fro sets up the electric impulses by induction. To speak plainly, the electric impulses correspond in form and character to the sound vibration which they represent. This reduced to a patent "claim" governed the art as firmly as a papal bull for centuries enabled Spain to hold the Western world. The language of the claim is: "The method of and apparatus for transmitting vocal or other sounds telegraphically as herein described, by causing electrical undulations similar in form to the vibrations of the air accompanying the said vocal or other sounds substantially as set forth." It was a long time, however, before the inclusive nature of this grant over every possible telephone was understood or recognized, and litigation for and against the patent lasted during its entire life. At the outset, the commercial value of the telephone was little appreciated by the public, and Bell had the greatest difficulty in securing capital; but among far-sighted inventors there was an immediate "rush to the gold fields." Bell's first apparatus was poor, the results being described by himself as "unsatisfactory and discouraging," which was almost as true of the devices he exhibited at the Philadelphia Centennial. The new-comers, like Edison, Berliner, Blake, Hughes, Gray, Dolbear, and others, brought a wealth of ideas, a fund of mechanical ingenuity, and an inventive ability which soon made the telephone one of the most notable gains of the century, and one of the most valuable additions to human resources. The work that Edison did was, as usual, marked by infinite variety of method as well as by the power to seize on the one needed element of practical success. Every one of the six million telephones in use in the United States, and of the other millions in use through out the world, bears the imprint of his genius, as at one time the instruments bore his stamped name. For years his name was branded on every Bell telephone set, and his patents were a mainstay of what has been popularly called the "Bell monopoly." Speaking of his own efforts in this field, Mr. Edison says: