connected with the Telephone. 289 



their way into telephonic circuits. Hence a telephone circuit 

 which may work well in dry fine weather will prove absolutely 

 unworkable in wet weather. 



Another source of trouble arises from what are technically 

 called " bad earths." It is almost impossible to make a perfect 

 connexion with the earth. There is always some resistance 

 at that point ; so that if two wires terminate on the same earth- 

 plate, the one being a working circuit and the other a telephone- 

 circuit, some currents from the former are sure to pass through 

 the latter and disturb the telephone. A return wire perfectly 

 cures this evil. 



There are other disturbing elements that are peculiar. 

 Earth-currents, which are always present in the wires, produce 

 a peculiar crackling noise, similar to that produced by a current 

 from a single fluid battery such as a Smee or a Leclanche, not 

 unlike the rushing of broken water. This is due to the pola- 

 rization of the earth-plate, as the sounds produced by a battery- 

 current are due to the polarization of the negative plate. 

 When auroras are present these earth-currents become very 

 powerful, and the sounds are much intensified. The effects 

 of thunderstorms are very peculiar : a flash of lightning, even 

 though so distant as to be out of sight, will produce a sound ; 

 and if it be near enough to be only sheet lightning, it produces, 

 according to Dr. Channing, of Providence, a sound like the 

 quenching of a drop of melted metal in water, or the sound of 

 a distant rocket. Moreover he says that this sound is heard 

 before the flash is seen, proving the existence of some induc- 

 tive effect in the air prior to the actual discharge. The tele- 

 phone thus becomes an admirable warning of the approach of 

 a thunderstorm. 



Sometimes a peculiar wailing sound is heard, which an 

 imaginative correspondent of mine likened to " the hungry 

 cry of newly-hatched birds in a nest." I am inclined to think 

 that it is due to the swinging of the wires across the magnetic 

 lines of force of the earth. It is not difficult to conceive that 

 these vibrations may succeed each other in the necessary 

 rhythmic order to produce musical tones. 



The wires are never free from sound ; and every change of 

 temperature or of the electric condition of the atmosphere is 

 recorded on this delicate apparatus. 



The expansion of the iron diaphragm under the influence 

 of the warm and damp breath when the telephone is first raised 

 to the lips preparatory to talk is very marked ; it produces a 

 faint rustling shiver. 



Immediately on the introduction of the instrument, great 

 anxiety was felt to learn its performance on submarine cables. 



Phil Mag. S. 5. Vol. 5. No. 31. April 1878. U 



