338 NINETEENTH CENTURY. PT. TIT. 



ment to perfection. Page in America, de la Rive and Reiss 

 on the Continent, and Varley in England, have all made 

 attempts to produce speaking at a distance, while Elisha 

 Gray of Chicago produced an instrument working with a 

 battery, by means of which vocal sounds could be trans- 

 mitted. But to Professor Graham Bell of Boston is due 

 the credit of having in 1876 at last succeeded in making a 

 telephone of the simple construction now used. Fig. 7 T is 

 a drawing of the telephone with a section of it by the side ; 

 one of the wires fastened to the end of the instrument is 

 carried across the country and fixed at the other end to 

 another instrument exactly like it ; the other wire is con- 

 nected with the earth. We have seen, p. 376, that Faraday 

 was able to produce a powerful electric current in a coil of 

 wire by drawing a magnet in and out of the centre of the 

 coil In Bell's telephone a permanent magnet, d, has a piece 

 of soft iron, ^, fastened to one end of it, and round this soft 

 iron is a coil of silk-covered copper wire. At a little dis- 

 tance from the soft iron bar is placed an iron plate, a, with 

 an opening above it in the wooden case enclosing it, and 

 into this opening the person speaks. The vibrations of the 

 voice make the particles of the iron plate or diaphragm 

 vibrate, so that the plate does not move up and down as a 

 whole, but more probably quivers, as it were, throughout its 

 whole surface. This vibration affects the soft iron bar, which, 

 it must be remembered, is not a permanent magnet, but only 

 made so by touching the permanent magnet below. So the 

 magnetisation of the soft iron is altered at every sound 

 according to the rate at which it vibrates and the form of 

 the vibration. This alteration at once sets up electric cur- 

 i\.nts in the coil of wire c, and these pass along the wire 

 instantaneously to the person at the other end, even if they 

 are miles away. This person holds an exactly similar 



