Contents 



in several coils instead of one Experiments with a 

 large electro-magnet excited by nine distinct coils 

 Uses a battery so powerful that electro-magnets are 

 produced one hundred times more energetic than those 

 of Sturgeon. Arranges a telegraphic circuit more than 

 a mile long and at that distance sounds a bell by 

 means of an electro-magnet. ..', ... 23 



ILES, GEORGE 



THE FIRST ATLANTIC CABLES 



Forerunners at New York and Dover. Gutta-percha 

 the indispensable insulator. Wire is used to sheathe 

 the cables. Cyrus W. Field's project for an Atlantic 

 cable. The first cable fails. 1858 so does the second 

 cable 1865. A triumph of courage, 1866. The 

 highway smoothed for successors. Lessons of the 

 cable. . . . . .' 37 



BELL, ALEXANDER GRAHAM 

 THE INVENTION OF THE TELEPHONE 



Indebted to his father's study of the vocal organs as 

 they form sounds. Examines the Helmholtz method 

 for the analysis and synthesis of vocal sounds Sug- 

 gests the electrical actuation of tuning-forks and the 

 electrical transmission of their tones Distinguishes 

 intermittent, pulsatory and undulatory currents. 

 Devises as his first articulating telephone a harp of 

 steel rods thrown into vibration by electro-magnetism. 

 Exhibits optically the vibrations of sound, using a 

 preparation of a human ear: is struck by the efficiency 

 of a slight aural membrane. Attaches a bit of clock 

 spring to a piece of goldbeater's skin, speaks to it, an 

 audible message is received at a distant and similar 

 device. This contrivance improved is shown at the 

 Centennial Exhibition, Philadelphia, 1876. At first 

 the same kind of instrument transmitted and delivered 

 a message; soon two distinct instruments were in- 

 X 



