504 



NATURE 



\_7iily 29, 1 8 So 



Besides this cause three others were traced in the course 

 of my experiments : Electrostatic action, external magnetic 

 action, and internal magnetic action. 



The following experiment was made with a very fine palladium 

 silver wire, about 13 cm. long, as sounder. I connected the 

 violin and microphone with four Bunsen's cells in circuit witli 

 the primary of a small induction coil (resistance of primary -27, 

 resistance of secondai7 44), while the wire telephone was put in 



circuit with the secondary. With this arrangement the music 

 was reproduced quite audibly, although the quality of the notes 

 was "wiry." This small coil had a movable core, consisting of 

 a bundle of iron wires, and the sound was louder with than 

 without the core. 



I next tried a more powerful induction-coil (resistance of 

 primary -3, secondary 320), all the other arrangements being 

 unaltered. The music could then be iust heard, but no more. 



Fig. I. — Iron. — a, sound very feeble at the tempemture of the air; B, high note distinctly heard and increasing: c, feeble fizz now he.ird ; d. fizr 

 increased ; E, quality of sound deepening : f, low note heard; G, sound very loud, low. medium, and high notes and buzz; H, no falling off : i, falling 

 off now evident ; j, marked diminution ; K, fizz very soft, nearly gone ; l, high note left ; m, silence. 



A large and very powerful induction-coil (resistance of secondary 

 about 10,000), tried under similar circumstances, gave no result 

 whatever. 



Electrostatic Action. — As I have said, nothing was heard with 

 the large induction coil when the secondary circuit was closed ; 

 but when it was interrupted at a mercury break, a loud hissing, 

 rattling noise was heard. This could not have come liy 

 mechanical transmission from the induction-coil, which was 

 several rooms off, the line \\ires being hung to the walls and 

 jammed over three doors. It had its seat at the mercury pools 

 of the break, and was doubtless due to electrostatic action. 



Similar sounds, only weaker, were observed with the smaller 

 Ruhmkorf when the circuit was broken. 



If two small disks separated by a small air-interval were 

 made the terminals of an induction-coil, in the primary of which 

 an interrupted ciu'rent flows, they would form a condenser, and 

 tlie difference of potential between them would vary in unison 

 \^ ith the primary current. Consequently the electrostatic force 

 of attraction would vary, and the disks, being set into vibration, 

 would act as a telephone. The sounds in Thomson's singing 

 condenser are probably due to this cause. 



I have not attempted to carry this idea into practice, but I 



SUd 



Fig. 2. — Steel. — a, fizzing sound and high note, 



, sharp fizz : E, buzz'.ng s 



i general increase 



believe that telephones have been made on this principle by 

 Edison and others. 



External Magnetic Action. — If the stretched wire of the 

 telciilione be brougjit into a magnetic field so as to cross the 

 lines of force, and an interrupted current passed, loud sounds are 

 wk'"''' ^ "^'^'^ " tuning-fork interrupter with two Bunsen's cells. 

 When a thick copper wire was put into the telephone, at first 

 nothing whatever was heard ; but when a horse-shoe magnet 



was brought up, and held with its plane perpendicular to the 

 wire, the note of the fork was heard vei7 loud (much louder than 

 in the neighbourhood of the fork itself, in fact), and compara- 

 tively pure. Little or none of the hissing or buzzing sound of 

 which I shall have to speak by and by can be got in this way. 

 It makes no great difference to the sound produced in this way 

 whether we use a wire of 2 mm. diameter or a wire "3 mm. in 

 diameter. With the thin wire, however, the visible amplitude 



