After Professor Hughes had published his discovery of the microphone, Edison, recognising, perhaps, that it and the carbon transmitter were based on the same principle, and having learnt his knowledge of the world in the hard school of adversity, hastily claimed the microphone as a variety of his invention, but imprudently charged Professor Hughes and his friend, Mr. W. H. Preece, who had visited Edison at Menlo Park, with having 'stolen his thunder.' The imputation was indignantly denied, and it was obvious to all impartial electricians that Professor Hughes had arrived at his results by a path quite independent of the carbon transmitter, and discovered a great deal more than Edison had done. For one thing, Edison believed the action of his transmitter as due to a property of certain poor or 'semi-conductors,' whereby their electric resistance varied under pressure. Hughes taught us to understand that it was owing to a property of loose electrical contact between any two conductors. The soft and springy button of lamp-black became no longer necessary, since it was not so much the resistance of the material which varied as the resistance at the contacts of its parts and the platinum electrodes. Two metals, or two pieces of hard carbon, or a piece of metal and a piece of hard carbon, were found to regulate the current in accordance with the vibrations of the voice. Edison therefore discarded the soft and fragile button, replacing it by contacts of hard carbon and metal, in short, by a form of microphone. The carbon, or microphone transmitter, was found superior to the magneto-electric transmitter of Bell; but the latter was preferable as a receiver to the louder but less convenient chemical receiver of Edison, and the most successful telephonic system of the day is a combination of the microphone, or new carbon transmitter, with the Bell receiver.