vice versa, by the motion of a magnet near a coil of wire. This is how an ordinary shocking coil is made. Here is a large permanent magnet and here is a coil of wire. I suddenly move that coil of wire, a current is produced, and I have rung a bell. But even if the magnet be fixed and the coil be fixed, any variation in the strength of the magnetism about that coil will produce a current of electricity in that coil. Thus if in front of that magnet which has a coil fixed on its pole, I move this mass of iron, a current will be produced in that

FIG. 3.

coil. And for every motion of that piece of iron I can produce a current of electricity. But more than that, the current will rise and fall in intensity exactly as the iron moves. Hence the currents of electricity produced in that coil will vary exactly as the motion of that mass of iron. Now suppose that mass of iron to be a thin disc like our parchment drum-head, but of iron; and I speak to that disc. We know that that disc will respond to my voice. Whatever words I sound, however I vary them in pitch and loudness and quality, that disc will vibrate in number, amplitude and form, exactly responsive, and currents of electricity will be produced in that coil which will vary exactly in number, strength, and form, with the words I utter. Let this coil be connected with an exactly similar coil at some distance off, and let the currents in the first coil circulate through the second, then if the second coil surround a mass of soft iron, these currents will induce magnetism in the soft iron, and the strength of this magnetism will vary exactly with the currents producing it. If in front of this iron coil we plant an iron disc exactly like the first one, then every time the iron coil is magnetised it will attract the iron disc, and will cause it to move. Now the motions of this disc will vary exactly with the variation of the magnetism of the coil. The magnetism of the coil will vary exactly with the strength of the currents producing it. The strength of the currents will vary exactly with the motions of the first disc, and hence the motions of the second disc will vary exactly with those of the first. In fact they will be an exact reproduction of the first. Hence with whatever note the first disc vibrates, however much it varies in pitch and loudness and quality, the second disc reproduces those vibrations exactly. Those vibrations are imparted to the air and thus we have sounds reproduced

with all the delicate variations of the human voice. The sound of the human voice is transmitted into electric currents, and these currents again produce sonorous vibrations which exactly reproduce the human voice. Indeed, there is no sound which the human lips can produce or the human ear can detect, which cannot be reproduced on the telephone, and where it not for practical difficulties, sounds that "mellow to sadness now madden to crime," could be as easily transmitted from the east to the west as from this hall to the room above. In fact, to "waft a sigh from Indus to the Pole," is removed from the poet's dreamland, and has become as much a matter of fact as ex"tracting sunbeams from cucumbers."

66

But not yet-the vapourings of imaginative newspaper corre spondents are not yet practical. The articulating telephone itself is an extremely delicate apparatus. It is subject to interference by every waif and stray current that wanders into a telegraph wire, and their name is legion. Atmospheric electricity, earth currents and the influence of neighbouring wires, all generate these troublesome wanderers and interfere with its action. So that on existing lines of telegraph, except for short distances, it has not yet been found useful or even practical, but on short independent isolated lines like those used for field telegraphs, it is a thorough practical instrument, and well deserving the fullest trial that actual service can give it.

It works to perfection in mines. There it is not only free from all extraneous troubles, but the silence of the grave facilitates the operation of its "still small voice." It is not even necessary in such places to put it to the ear. Wherever, however, extraneous sounds intervene not only is it necessary to put it close to the ear, but to effectively shut out all disturbing elements, two telephones are used, one to each ear. A bi-aural stethoscope applied to it is also found an useful adjunct. By its means reading is very simple. How far it could be heard amidst the roar of artillery and the din of battle remains to be tried.

What it does is this: it transmits to a distance far beyond the reach of the ear, or of the eye, the words of command, the tones of voice, the distinct and unmistakable articulation of the general as well as of the private. Such an apparatus must be valuable for military purposes.

How far it can be utilized for naval purposes remains to be seen. Wherever a wire can extend there can the voice be sent. In communicating between the bridge and the wheel, between the turret and the engine room, between the look-out and the officer of the watch, it ought to be useful. For diving operations it is invaluable. In torpedo operations and range-finding it may prove useful.

But at present it is a mere child. It has startled us all by its novelty, its beauty, and its simplicity. Time alone is required to establish its utility. Probably no instrument that has ever been devised has created more sensation, or has attracted so much attention, and I feel highly honoured in having been allowed to bring before such a distinguished audience the incomparable invention of Alexander Graham Bell.

Major WEATHERHEAD: I should like to ask how it happens that the vibration

continues so much longer in the case of the bell being struck, than it does in the case of the sound of the voice?

Mr. PREECE: The simple reason is, the vibrations of the bell are continuous if they are not rapidly stopped. When I take a whistle, blow it and stop, the sound ceases at once the moment you remove the source of the sound. But in the case of the bell, as in the case of the glass, the vibration continues. If you cause a finger glass to sound, you can see the musical wavelets on the surface of the water, which very prettily show the vibration of the body itself. There is a loss of power in the telephone however at a great distance; as the distance increases it has just the same effect as it would have upon the voice itself, for when a person speaks further and further away, the sounds come gentler and gentler; and in the telephone when you add resistance or increase the length of your line, so the voice seems to come from a greater and greater distance.

Captain MAYNE, R.N.: I should like to ask you how far the voice will go, and whether you have any idea of being able to communicate in this way across the Atlantic?

Mr. PREECE: I am not prepared to say that there is much hope of our talking across the Atlantic, but I think it possible to talk to distances greater than the distance across the Atlantic. The reason we cannot talk across the Atlantic is because there is a peculiar electric effect in submarine cable called induction; it is as though the electricity were absorbed by the gutta-percha, and small currents sent in at one end never arrive at the other. They get rolled up as it were into one, so that on a long submarine cable, instead of getting the finer sounds when the vibrations are rapid, they would all come out as one current, not producing any sound at all. It does not seem at present practicable to apply to a greater distance than 200 miles, but in the present day that man would be a very rash man who would affirm that it is impossible to do anything.

The CHAIRMAN: We must, I think, thank Mr. Preece very much for the interesting and able lecture that he has given us on the Telephone. There are probably few gentlemen who have had greater experience in telegraphy than Mr. Preece, who is a member of that department to which we all owe so much-the Postal Telegraph Department. I think that none will deny the great advantages of the telegraph, and there are few Officers who are not well aware of its great importance in the Army on service. I can hardly speak so much of the Navy, but I dare say that there the telegraph will also be of great use. There is no doubt that in all the cases that have been mentioned by Mr. Preece, it will be most valuable. There is one thing that I think will bear much on its advantages in the Army, viz., that it will do away with a great deal of difficulty in providing a sufficient number of telegraphers on service. Here every man will be as it were a trained telegrapher; a General will be able to speak through the telephone without having received any instruction in telegraphy. It only remains for scientific gentlemen to perfect this instrument, which can only as yet be considered as in its infancy. There lies the great labour, we must try experiments and endeavour to perfect it as soon as we can, and I am quite sure that the result will be to the great advantage of our services. In your name I beg to thank Mr. Preece for his interesting lecture.

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