graph Company), a good opportunity offered of testing this matter practically upon lengths of wire erected on both sides of a railway. To succeed in my experiment, and detect the very small amount of electricity likely to be available in such a case, I evidently required the aid of a very sensitive galvanometer, much more so indeed than the long pair of astatic needles and coil of the Cooke & Wheatstone telegraph, which was then in universal use as a detector. The influence of magnetism upon a wire conveying an electric current at once suggested itself to me, and I constructed a most sensitive instrument on this principle, by which I succeeded in obtaining actual signals between lengths of elevated wires about 120 ft. apart. This, however, suggested nothing more at the moment than that the current discharged from the earth-plates of one line found its way into the earth-plates of another and adjacent circuit, through the earth. Later on, I had other opportunities of verifying this matter with greater distances between the lines of wire, and ultimately an instance in which the wires were a considerable distance apart, and with no very near approach to parallelism in their situation. Then it was that it entered my head that telegraphing without wires might be a possibility."

The following extracts from the letter in the 'Mining Journal,' above referred to, may now be reproduced with interest. I have slightly altered the phraseology with a view of making the writer's meaning more clear and connected: 1

"Allow me, through the medium of your valuable

1 Mr Charles Bright has reprinted this letter verbatim in Jour. Inst. Elec. Engs.,' vol. xxvii. p. 958, as containing "the first really practical suggestion in the direction of inductive telegraphy "; but, as we now see, it is not the first suggestion, and it is certainly not inductive.

journal, to draw attention to a principle upon which a telegraphic communication may be made between England and France without wires. I take for certain (as experiments I have made have shown me) that when the poles of a battery are connected with any extended conducting medium, the electricity diffuses itself in radial lines between the poles. The first and larger portion will pass in a straight line, as offering the least resistance; the rays will then form a series of curves, growing larger and larger, until, by reason of increasing distance, the electricity following the outer curves is so infinitesimal as to be no longer perceptible.

"These rays of electricity may be collected within a certain distance-focussed as it were-by the interposition of a metallic medium that shall offer less resistance than the water or earth; and, obviously, the nearer the battery, the greater the possibility of collecting them. I do not apprehend the distance of twenty miles being at all too much to collect a sufficient quantity of electricity to be useful for telegraphic purposes. If, then, it is possible, as I believe, to collect in France some portion of the electricity which has been discharged from a battery in England, all that is required is to know how to deal with it so that it shall indicate its presence.

"The most delicate of the present telegraph apparatus, the detector, being entirely unsuited for the purpose, I propose the following arrangement: Upon one shore I propose to have a battery that shall discharge its electricity into the earth or sea, with a distance between its poles of five, ten, or twenty miles, as the case may be. Let a similar length of wire be erected on the opposite coast, as near to, and parallel with, it as possible, with its ends also dipping into the earth or sea. In this circuit place an instrument consisting of ten, twenty, or more round or square coils of the

finest wire of best conductibility, suspended on points or otherwise between, or in front of, the poles of an electro-, or permanent, magnet or magnets. Any current passing through the coil would be indicated by its moving or shifting its position with reference to the poles of the magnet. This would constitute a receiving apparatus of the most delicate character, for its efficiency would depend not so much on the strength of the current passing as on the power of the magnet, which may be increased at pleasure. "I hope some one will take up this suggestion and carry it out practically to a greater extent than my limited experiments have enabled me to do. Of its truth for long as well as for short distances I am satisfied, and only want of means and opportunity prevent me carrying it out myself."

In a recent letter to the writer àpropos of this early proposal, Mr Wilkins says:

"I will just say that all thought of induction was absent in my first experiments. I modified my views in this respect a year or two later, but I did not attach sufficient importance to the matter to follow up my communication to the 'Mining Journal,' especially as at that time a cable was actually laid across the Channel, which I could not doubt would be a success, and a permanent one too. I rather courted forgetfulness of the proposition. Whatever my

opinion at the time was as to the source of the electricity that I discovered in the far removed and disconnected circuit, the result was the same, and the means I used to obtain it the same in principle as those which make the matter an accomplished fact to-day-viz., elevated lengths of wire, and the discharge of electricity from the one on to a delicate receiving apparatus in the circuit of the other.

"As regards the form of receiving apparatus which I suggested for indicating the signals, I did then, and do now, attach great importance to the happy idea. It happens to

be the most delicate form of detector or galvanometer, and is identical in principle with Lord Kelvin's apparatus for long cable working, which, in his Siphon Recorder Patent, he says is as sensitive as his Mirror Galvanometer."

This principle, as the practical reader knows, has been largely used in telegraphy. Besides Lord Kelvin's application of it, we have the Brown and Allan Relay, the Weston Relay, and Voltmeter, and other contrivances of a similar nature;1 but Mr Wilkins was himself the first to put it in practice, and under the following interesting circumstances: In 1851 he went to America to assist Henry O'Reilly of New York, a well-known journalist, who had a concession from the patentees of the Morse system for the erection of telegraph lines, at a royalty per mile. Disputes soon arose, and the Morse Syndicate sought to prevent O'Reilly from using their relay, without which the Morse instruments would be useless for long distances. In this difficulty O'Reilly adopted Bain's electro-chemical apparatus, and employed it for a time on the People's Telegraph from New York to Boston, via Albany. But finding that it was impossible to use this instrument in connection with intermediate stations, O'Reilly was again in a difficulty, when Mr Wilkins came to the rescue by saying he could devise a relay which did not require an iron armature, or electromagnet of the ordinary form, and which would therefore be independent of the Morse patent. Very soon relays consisting of movable coils of wire, suspended between the poles of a magnet, were constructed in the workshop of John Gavitt, a friend of O'Reilly's, and then famous as a bank-note engraver. The instruments were placed in the

1 The germ of all these instruments, as well as the Axial Magnets of Prof. Page and Royal E. House, was sown by Edward Davy in England in 1837. See my 'History of Electric Telegraphy,' pp. 356,

circuit of the People's Telegraph, and O'Reilly was savedbut only for a time, as in the end he was beaten by his powerful opponents. The Wilkins relay was put aside and soon forgotten, but forty-three years later it was brought forward again by Mr Weston as an original invention.1

DR O'SHAUGHNESSY (AFTERWARDS SIR WILLIAM O'SHAUGHNESSY BROOKE)—1849.

One of the first difficulties encountered in the early days of the telegraph in India was the crossing of the great water-ways that abound in that country; and it was this difficulty which first directed the attention of Dr O'Shaughnessy, the introducer of the system in India, to the subject. of subaqueous telegraphy.

In 1849 he laid a bare iron rod under the waters of the river Huldee, 4200 feet wide, with batteries and delicate. needle instruments in connection on each bank. Signals were passed, but "it was found that the instruments required the attention of skilful operators, and that in practice such derangements occurred as caused very frequent interruptions."

He next tried the experiment without any metallic conductor, using the water alone as the sole vehicle of the electric impulses, but, though he again succeeded in passing intelligible signals, he found that the battery power for practical purposes would be enormous (he used up to 250 cells of the nitric acid and platinum form), and therefore prohibitively expensive.

Although for practical purposes he soon abandoned the idea of signalling across rivers with naked wires, and without any wires at all, O'Shaughnessy for many years took

1 See the New York 'Electrical Engineer,' February 21, 1894.