United States; a history: the most complete and most popular history of the United States of America from the aboriginal times to the present . nstitute of Technology. It should be mentioned,however, that Professor A. C. Dolbear, of Tufts College, Massachusetts, and Mr. Thomas A. Edison, of Menlo Park, New Jersey,have also succeeded in solving the original difficulties in the way oftelephonic communication, or at least in answering practically some ofthe minor questions in the way of Telephone may be defined as an instru-ment for the reproductionof sounds, particularly thesou
United States; a history: the most complete and most popular history of the United States of America from the aboriginal times to the present . nstitute of Technology. It should be mentioned,however, that Professor A. C. Dolbear, of Tufts College, Massachusetts, and Mr. Thomas A. Edison, of Menlo Park, New Jersey,have also succeeded in solving the original difficulties in the way oftelephonic communication, or at least in answering practically some ofthe minor questions in the way of Telephone may be defined as an instru-ment for the reproductionof sounds, particularly thesounds of the human voice,by the agency of electricity,at long distances from theorigin of the vocal disturb-ance. It is now well knownthat sound consists of awave agitation, communi-cated through some me-dium to the organ of hear-ing. Every particular soundhas its own physical equiv-alent in the system of wavesin which it is written. Theonly thing that is necessaryin order to carry a sound inits integrity to any distanceis to transmit its physicalequivalent, and to redeliverthat equivalent to some or-gan of hearing capable of receivingis created. TELEPHONE. it. Upon this idea the TelephoneEvery sound which falls by impact upon the sheet-iron diskof the instrument communicates thereto a sort of tremor; this tremorcauses the disk to approach and recede from the magnetic pole placedjust behind the diaphragm. A current of electricity is thus induced,pulsates along the wire to the other end, and is delivered to the me-tallic disk of the second instrument, many miles away, just as it was 656 HISTORY OF THE UNITED STATES. produced in the first. The ear of the hearer receives from the secondinstrument the exact physical equivalent of the sound or sounds whichwere delivered against the disk of the first instrument, and thus theutterance is received at a distance just as it was given forth. As already said, the invention of the Telephone stands chiefly tothe credit of Professors Gray and B
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