Chapter VII: Part 7

“Mr. Ronalds now fixed a circular brass plate, figure 37, upon the second arbour of a clock which beat dead seconds. This plate was divided into twenty equal parts, each division being worked by a figure, a letter, and a preparatory sign. The figures were divided into two series of the units, and the letters were arranged alphabetically, omitting J, Q, U, W, X and Z. In front of this was fixed another brass plate as shown in figure 38, which could be occasionally turned round by the hand, and which had an aperture like that shown in the figure at V, which would just exhibit one of the figures, letters and preparatory signs, for example, 9, _v_, and ready. In front of this plate was suspended a pith ball electrometer, B, C, figure 38, from a wire D, which was insulated, and which communicated on one side with a glass cylinder machine, and on the other side with the buried wire. At the further end of the buried wire, was an apparatus exactly the same as the one now described, and the clocks were adjusted to as perfect synchronism as possible.

“Hence it is manifest, that when the wire was _charged_ by the machine at either end, the electrometers at both ends _diverged_, and when it was discharged, they collapsed, at the same instant. Consequently, if it was discharged at the moment when a given letter, figure, and sign on the lower plate, figure 37, appeared through the aperture, figure 38, the same figure, letter and sign would appear also at the other clock; so that by means of such discharges at one station, and by marking down the letters, figures and signs, seen at the other, any required words could be spelt.

“An electrical pistol was connected with the apparatus, by which a spark might pass through it when the sign _prepare_ was made, in order that the explosion might excite the attention of the superintendent, and obviate the necessity of close watching.

_“Preparatory signs._ A, prepare; V, ready; S, repeat sentence; P, repeat word; N, finish; L, annul sentence; I, annul word; G, note figures; E, note letters; C, dictionary.”

_Electro Magnetism._

We have now to notice a discovery, which forms the basis of those modern telegraphs in which the principle of electro magnetism is adopted. The following is an extract from the “Library of Useful Knowledge,” in relation to the discovery:

“The real discoverer of the magnetic properties of electric currents M. Oersted, Professor of Natural Philosophy, and Secretary of the Royal Society of Copenhagen. In a work which he published in the German, about the year 1813, on the identity of chemical and electrical forces, he had thrown out conjectures concerning the relations subsisting between the electric, galvanic and magnetic fluids, which he conceived might differ from one another only in their respective degrees of tension. If galvanism, he argued, be merely a more latent form of electricity, so magnetism may possibly be nothing more than electricity in a still more latent form; and he, therefore, proposed it as a subject worthy of inquiry, whether electricity employed in this, its most latent form, might not be found to have a sensible effect upon a magnet. It is difficult clearly to understand what he meant by the expression of _latent states_, as applied to electricity, but it may be sufficient for us to know, that in the various endeavours he subsequently made to verify his conjectures, he was led to such forms of experiment as afforded decisive indications of the influence of Voltaic currents on the magnetized needle. Yet, even after he had succeeded thus far, it was a matter of extreme difficulty to determine the real direction of this action, and it was not till the close of the year 1819, that his perseverance was at length rewarded by complete success.

“The first account of his discovery that appeared in England is contained in a paper, which he himself communicated, in Thompson’s Annals of Philosophy, for October, 1820, vol. 16, page 273; and in which the following experiments are described. The two poles of a powerful Voltaic battery were connected by a metallic wire, so as to complete the galvanic circuit. The wire which performs this office he called the _uniting_ wire; and the effect, whatever it may be, which takes place in this conductor, and in the space surrounding it, during the passage of the electricity, he designates by the term _electric_ conflict, from an idea that there takes place some continued collision and neutralization of the two species of electric fluids, while circulating in opposite currents in the apparatus. Then taking a magnetic needle, properly balanced on its pivot, as in the mariner’s compass, and allowing it to assume its natural position in the magnetic meridian, he placed a straight portion of the uniting wire horizontally above the needle, and in a direction parallel to it; and then completed the circuit, so that the electric current passed through the wire. The moment this was done, the needle changed its position, its ends deviating from the north and south towards the east and west, according to the direction in which the electric current flowed, so that by reversing the direction of the current the motion of the needle was also reversed. The general law he expressed as follows: ‘That end of the needle which is situated next to the negative side of the battery, or towards which the current of positive electricity is following, immediately moves to the westward.’

“The deviation of the needle is the same, whether the uniting wire, instead of being immediately above the needle, be placed somewhat to the east or west of it, provided it continue parallel to and also above it. This shows that the effect is not the result of a simple attractive or repulsive influence, for the same pole of the magnetic needle which approaches the uniting wire, when placed on its east side, recedes from it when placed on its west side.”

[20]“Soon after this important discovery of Oersted’s was made, M. Ampère established the second fundamental law of electro magnetism, that the two conducting wires from the poles of the battery, when conveniently suspended, _attracts each other when they transmit electrical currents moving in the same direction, and repel each other when the currents which they transmit have opposite directions_.

[20] Encyclopedia Britannica, vol. 21, p. 686.

“On the 25th Sept. 1820, M. Arago communicated to the French Institute the important discovery that the electrical current possesses, in a very high degree the power of developing magnetism in iron or steel. Sir H. Davy communicated a similar fact to Dr. Wollaston on the 12th of November, 1820, and Dr. Seebeck laid before the Royal Academy of Berlin a series of experiments on the same subject.

“M. Arago found that the uniting wires of a powerful Voltaic battery attracts iron filings often with such force as to form a coating around the wire ten or twelve times thicker than itself. This attraction, as he found, did not originate in any magnetism previously possessed by the iron filing, which he ascertained would not adhere to iron, and that it was not a case of common electrical attraction, was evident from the fact that copper and brass filings were not attracted by the uniting wire. M. Arago likewise found, that the iron filings began to rise before they came in contact with the uniting wire; and hence he drew the conclusion, that the electric currents converted each small piece of iron into a temporary magnet. In following out this view, the French philosopher converted large pieces of iron into temporary magnets and also small steel needles into permanent ones, (by employing the helix.) Sir H. Davy and Dr. Seebeck obtained analogous results without knowing what had been previously done in France.

“A galvanometer was first constructed by Professor Schweigger, of Halle, very soon after the first discovery of electro magnetism, and by him called an _electro_ magnetic multiplier.”

In the year 1820, Ampère predicted the possibility of making the deflection of the magnetic needle, by the agency of the galvanic fluid, serve the purposes of transmitting intelligence. In page 19 of his memoir, he thus resolves the problem:

“As many magnetic needles as there are letters of the alphabet,” he says, “which may be put in action by conductors; which may be made to communicate successively with the battery by means of keys; which may be pressed down at pleasure, might give place to a telegraphic correspondence which would surmount all distance and would be as prompt as writing speech to transmit thought.”

“The next step in the progress of discovery, was that of making magnets of extraordinary power by means of a galvanic battery. This seems to have been first accomplished by Prof. Moll, of Utrecht, and Professor Henry, of Princeton, who was able to lift thousands of pounds weight by his apparatus.”

_The following Extract is taken from a Work on Electro Magnetism published by Jacob Green, M. D. Professor of Chemistry in Jefferson Medical College, 1827._

“In the very early stage of electro magnetic experiments, it had been suggested, that an instantaneous telegraph might be constructed by means of conjunctive wires, and magnetic needles. The details of this contrivance are so obvious, and the principles on which it is founded so well understood, that there was only one question which could render the result doubtful. This was, whether by lengthening the conjunctive wires, there would be any diminution in the electrical effect upon the needle. It is the general opinion, that the electrical fluid, from a common electrical battery, may be transmitted, without any sensible diminution, instantaneously, through a wire three or four miles in length. At the philosophical dinner, as it has been called, got up a number of years ago by some gentlemen of Philadelphia, on the banks of the Schuylkill, it may be recollected that Dr. Franklin killed a turkey with the electric shock, transmitted across the river, a distance of more than half a mile; and Dr. Watson, who was also at the pains of making some experiments of this kind, asserts that the electric shock was transmitted, instantaneously, through the length of 12,276 feet. Had it been found true that the galvanic fluid could be transmitted in a moment through a great extent of conducting wire, without diminishing its magnetic effect then no question could have been entertained as to the practicability and importance of the suggestion adverted to above, with regard to the telegraph. Mr. Barlow, of the Royal Military Academy, who has made a number of successful experiments and investigations in electro magnetism, fully ascertained that there was so sensible a diminution with only 200 feet of wire, as to convince him at once of the impracticability of the scheme.

_Triboaillet’s Proposition._

[21]“In 1828, M. Victor Triboaillet de Saint Amand proposed to establish a correspondence from Paris to Brussels, by placing along the highway, and at some feet deep, a metallic wire, about a line or a line and a half diameter. He recommended to cover the wire with shellac, upon which was to be wound silk, very dry, which should be covered in their turn with a coating of resin. The whole was then to be put into glass tubes carefully luted up with a resinous substance and secured by a last envelope in the earth, then varnished over and hermetically sealed. Then, by means of a powerful battery, he would communicate the electricity to the conducting wire, which would transmit the current to the opposite point to an electroscope, destined to render sensible the slightest influence, and left to each one to adopt at pleasure the number of motions to express the words or letters which they might need.”

[21] Report of Academy of Industry, Paris.

_Fechner’s Suggestion._[22]

“Fechner, in his manual of galvanism, (Voss, 1829, page 269,) remarked, that the electro magnetic effects of the galvanic current would be far more appropriate for the giving of signs than Soemmering’s plan by the decomposition of water.”

He suggested that wires, having twenty-four multiplicators should be extended between Leipsic and Dresden, and there connected, alternately, with a galvanic column, for telegraphic purposes. Indeed, he ventured to prophecy, that probably hereafter such a connection between the central point of a kingdom, and different provinces might be arranged as there was existing in animal bodies, between the central point of organic structure of particular members and nerves.

[22] Polytechnic Central Journal, 1838.

_Magneto Electricity._

We come now to give an account of a new branch in the science of electricity, viz. _magneto electricity_; which Dr. Faraday was the first to discover in the year 1831. As this species of electricity has been applied to several of the plans of electric telegraphs, which we shall describe, it is desirable that some account should be given of its discovery, and of the instrument by which it is generated.

The following is an extract from “Daniell’s Introduction to Chemical Philosophy” 2d edition, London, 1843.

“The phenomena of electro magnetism are produced by _electricity in motion_; accumulated electricity, when _not in motion_, exerts no magnetic effects. Dr. Faraday early felt convinced that “as every electric current is accompanied by a corresponding intensity of magnetic action at right angles to the current, good conductors of electricity, when placed within the sphere of this action, should have a current induced through them, or some sensible effect produced, equivalent in force to such a current.” These considerations, with their consequence, the hope of obtaining electricity from ordinary magnetism, stimulated him to investigate the subject experimentally, and he was rewarded by an affirmative answer to the question proposed. He thus became, like Oersted, the founder of an entirely new branch of natural philosophy.

“If a wire connecting the two ends of a delicate galvanometer be placed parallel and close to the wire connecting the poles of a Voltaic battery, no effect will be produced upon the needle, however powerful the current may be. If the points opposed in the two wires be multiplied by coiling the one, as a helix, _within the convolutions_ of the other, coiled in the same way, both being covered with silk to prevent metallic contact, still no effect will be discernible so long as the current is _uninterrupted_. When, however, the current of the battery is stopped by breaking the circuit, the needle is momentarily deflected, as by a wave of electricity passing in the same direction as that of the main current. Upon allowing the needle to come to a state of rest, and then renewing the contact, a similar impulse will be given to it in the contrary direction. While the current continues, the needle returns to its state of rest, again to be deflected in the first direction by stopping the current. Motion may be accumulated to a considerable amount in the needle, by making and breaking the contacts with the battery in correspondence with its swing. The same effects are produced when, the current being uninterrupted, the conducting wire is made suddenly to approach or recede from the wire of the galvanometer. As the wires approximate, there will be a momentary current induced in the direction contrary to the inducing current; and as the wires recede, an induced current in the same direction as the inducing current.

“As this _Volta electric induction_ is obviously produced by the transverse action of the Voltaic current, in one case, by the _mechanical_ motion of the wire, and in the other at the moments of _generation_ and _annihilation_ of the current, Dr. Faraday thought that the sudden induction and cessation of the same magnetic force in soft iron, either by the agency of a Voltaic current, or by that of a common magnet, ought to produce the same results. He constructed a combination of helices (8) upon a hollow cylinder of pasteboard: they consisted of lengths of copper wire, containing, altogether, 220 feet; four of these were connected end to end, and then with the galvanometer. The other intervening four were also connected end to end, and then with the Voltaic battery. In this form a slight effect was produced upon the needle by making and breaking contact. But when a soft iron cylinder, seven-eighths of an inch thick and twelve inches long, was introduced into the pasteboard tube, surrounded by the helices, the induced current affected the galvanometer powerfully. When the iron cylinder was replaced by an equal cylinder of copper, no effect beyond that of the helices alone was produced.

“Similar effects were then produced by _ordinary magnets_. The hollow helix had all its elementary helices connected with the galvanometer, and the soft iron cylinder having been introduced into its axis, a couple of bar magnets were arranged with their opposite poles in contact, so as to resemble a horse-shoe magnet, and contact was then made between the other poles and the ends of the iron cylinder, by which it was converted, for the time, into a magnet; by breaking the magnetic contacts, or reversing them, the magnetism of the iron cylinder could be destroyed or reversed at pleasure. Upon making magnetic contact, the needle was deflected; continuing the contact, the needle became indifferent, and resumed its first position; on breaking contact, it was again deflected, but in the opposite direction to the first effect, and then it again became indifferent. When the magnetic contacts were reversed, the deflections were reversed. The actual contacts of the magnets with the soft iron is not essential to the success of these experiments, for their near approximation induces sufficient magnetism in the cylinder to generate the electric current, which affects the needle. The first rise of the magnetic force induces the electric wave in one direction; its sudden decline, in the opposite. Mechanical motion of a permanent magnetic pole in one direction, across the coils of the helix, will produce the same effect as the sudden induction of the magnetism in the soft iron, and its motion in the opposite direction will cause a corresponding effect with its annihilation, when the soft iron cylinder is removed from the helix, and one end of a cylindrical magnet thrust into it, the needle is deflected in the same way as if the magnet had been formed, by either of the two preceding processes. Being left in, the needle will resume its first position, and then being withdrawn, the needle will be deflected in the opposite direction. On substituting a small hollow helix, formed round a glass tube, for the galvanometer, in these experiments, and introducing a steel needle, it will be converted into a magnet, provided care be taken not to expose it to the opposite action of the reverse current; and if the continuity of the conducting wire be broken, at the moment when the secondary electric wave is passing through it, a bright spark may be obtained.

“The connection of electro magnetical and magneto electrical phenomena may be exhibited in a very striking way, by employing any of the apparatus, by which the rotary motions of the _magnet_ or _conducting wire_, are produced by a current of electricity, to generate electric currents by the mechanical rotations of the magnet or wire. For this purpose, the galvanometer may be substituted for the battery, and when the wire is made to turn round the pole of the magnet, or the pole of the magnet round the wire, in one direction, the needle will be deflected to one side; and to the other by the opposite rotation. Nothing can be better shown that _magneto electric_ is the _converse_ of _electro_ magnetic action.

“Dr. Faraday by rotating a copper disc between the poles of a horse-shoe magnet, produced a constant current of electricity in one direction, and deflected the needle of the galvanometer; one wire being connected with the disc, and the other with the arbour. By turning the disc in one direction, the circuit will pass from the axis to the circumference; by turning it in the opposite direction, the current will flow from the circumference to the axis.”

Figure 39 represents a side view of the instrument. B shows the copper disc permanently secured upon its axis, and which is turned by means of the crank, E. G represents one of the standards which support the axis. H is the platform upon which the various parts are arranged. The edge, C, of the copper disc, is amalgamated so as to make a perfect connection with the amalgamated segment, _a_, to which is soldered a wire, I, leading to the galvanometer. That portion of the disc, B, which is shaded, is not amalgamated. J is the other wire proceeding from the galvanometer, and both it and the axis are amalgamated, at the points of connection. A is the permanent magnet, with its poles on each side of the copper disc, B, opposite the amalgamated portion of the rim.

Figure 40, represents a top view of the instrument, H is the platform; C the disc; _a_ the segment; A the permanent magnet; J the wire attached to the axis, P; G and G are the two standards. E the crank; and I the wire attached to the segment _a_.

Mr. Saxton,[23] in a letter to Mr. Lukens, dated, London, April 14th, 1832, after describing Dr. Faraday’s rotating disc, figures 39 and 40, says, “I have made this experiment in a different way, and succeeded satisfactorily. The method was as follows: A coil of wire wrapped with silk, similar to that used in the galvanometer, was attached, by the ends, to the wires of the galvanometer. On passing this roll, backward and forward, upon one of the poles of a horse-shoe (permanent) magnet, or placing it upon and removing it from either pole, I have made the needle of the galvanometer to spin round rapidly.” Figure 41, represents Mr. Saxton’s plan.

[23] We here introduce to the reader our ingenious and scientific country man, Mr. Joseph Saxton, formerly of the United States mint, Philadelphia, but now connected with the Department of weights and measures, at Washington, who invented the first Rotary Magneto Electric Machine, and which has now been extensively adopted.

N and S represent the north and south poles of the horse-shoe permanent magnet. C is the coil of wire, wound round a spool of an oblong shape, through the centre of which there is an opening sufficiently large to admit either of the prongs of the magnet through it. A and B are the ends of the wire leaving the coil, and are connected with the galvanometer.

Mr. Saxton on the 2d of May, 1832, obtained the spark by the following arrangement of the permanent magnet and the helix of wire round the armature. In relation to this instrument, he thus writes to Mr. Lukens, of Philadelphia, dated, London, May 11th, 1832. Jour. Frank. Int. vol. 13, p. 67. “Since my last I have heard of a method of producing a spark from a magnet, discovered I think by an Italian.[24] This experiment I made at once upon a large horse-shoe magnet, which I am making for Mr. Perkins and his partners. One of your large magnets will answer the same purpose. Make a cylinder of soft iron of an inch, or three-fourths of an inch, in diameter, and of the usual length of the keeper; place two discs of brass or wood upon this cylinder, and at such a distance apart that they will conveniently pass between the poles of the magnet; between these wind, say fifty feet of bobbin wire, which may be of iron covered with cotton; let the ends of this coil be bent over the ends of the cylinder and brought down until they touch the poles of the magnet. The ends should be of such a length, that on bringing the cylinder to the magnet, one of the ends will touch, when the cylinder is about half an inch from the magnet, and the other at one-fourth of an inch. The cylinder being thus arranged, and in contact with the magnet, on drawing it suddenly away a spark will pass between the end of the wire, and the pole of the magnet.”

[24] M. M. Nobili and Antinori.

Figure 42 represents the instrument as first constructed by Mr. Saxton, in London.[25] A and B are the ends of the helix, surrounding the cylindrical bar of soft iron between E and F, filling the cavity which has been formed out of the solid iron. The size of bar between the collars E and F, thus formed, is the same as the projections H and G. The wire, _a_, proceeds from the outside of the coil and makes a suitable contact upon the prong, A, of the magnet: _b_ proceeds from the bottom of the coil, where the winding commenced and makes a similar contact upon the prong, B, of the permanent magnet. One wire extends a little further upon the magnet than the other, so that the shorter one may break its connection sooner than the longer. H and G are projections from the sides of the armature, to which the handle, D, is secured. Let the armature, with its helix, be held up against the ends of the prongs of the permanent magnet; and the wires _a_ and _b_, in perfect contact with their respective prongs, as shown in the figure; if, while in this condition, the keeper is suddenly withdrawn, a spark will appear at the end of the short wire, as it breaks its contact with the prong of the magnet.

[25] Mr. Saxton on the 3d of May exhibited his apparatus, and the mode of obtaining the spark to Dr. Ritchie, Messrs. Thomas Gill, John Isaac Hawkens and Steadman Whitwell. On the 8th of May he loaned it to Dr. Ritchie, who publicly exhibited it at a lecture, at the London University, and also at the London Institution, Finsbury.

Mr. Saxton, however, was still further successful, the following year, in carrying out an idea which occurred to him on the 6th of December, 1832, of producing the same phenomena, with a more convenient and powerful rotating instrument.[26] This new arrangement he was able to test on the 20th of June, 1833, and obtained the spark. On the 22d, he made an unsuccessful attempt, in the presence of Prof. Rogers, of Philadelphia, at the decomposition of water. On the 30th of June he exhibited it at a meeting of the British Association at Cambridge, before Dr. Faraday, Dr. Brewster, Prof. Forbes, Dr. Dalton, and many other distinguished and scientific gentlemen. The experiments made by it were the exhibition of the spark, giving shocks, &c. On the third of July, Mr. Saxton succeeded in decomposing water, by adding a little sulphuric acid, and on the 25th of August, he ignited and melted platinum wire.

[26] In relation to this instrument, Prof. Daniell makes the following remarks: “After Dr. Faraday’s discovery of _Volta electric_ and _magneto electric_ induction, many ingenious contrivances were made for exalting the effects and facilitating experiments. The most complete arrangement now in use, was the original combination of Mr. Saxton.”

Figure 43 exhibits a side view of the instrument: _a_, _a_, _a_, is a compound permanent magnet, consisting of three steel plates, put together, side by side. B and C are two wooden supports, upon the platform A A. To these supports the magnet is permanently secured, by a yoke, S, through which pass two screws into the wooden supports below. M is a cross bar, into which, and at right angles with it, are screwed two arms of round soft iron, R, about five-eighths of an inch in diameter, the whole forming the armature or keeper of the magnet. Upon these two projecting arms, are placed two coils, D′ and D, of copper wire, insulated with silk. The whole is very securely fastened upon the steel spindle, N, which has its journals in the supports, B and B′. On the end of the spindle, N, near the curve of the magnet, there is a small band pulley, F, which is driven by the band or cord of the large wheel, E, and the crank, J. The axis of the large wheel passes through a long socket, L, in the top of the column, H; on one end of the axis the band wheel is fastened and on the other the crank. By this arrangement a very rapid and quiet rotary motion is given to the armature.

In the column, H, there is a socket, into which the stem of the upper part of the column, G, is fitted, which admits of the large wheel being raised or lowered, so as to prevent the band from slipping, and when properly adjusted it is secured by the screw, I. O is an ivory hub, sliding over that part of the spindle immediately projecting beyond the cross bar, M. Upon this ivory hub is a copper disc, C, with a socket, _n_: _b_, is a needle made of platinum, which, with its socket, _m_, is nicely fitted upon the end of the steel spindle, so as to be adjusted to any required angle with the armature, and when adjusted to retain its position. The two ends of the two coils, which leave the _centre_ of the helices, are made to form a contact with the soft iron arms, R R, passing through the coils, D′ and D, thus making the circuit complete with the needle _b_, upon the end of the spindle, N, by a continuous metallic connection of the arms, with the cross bar, M, and through the cross bar to the spindle, N, in contact with the needle, _b_. The two ends of the two coils, leaving the _outside_ of the helices, are joined in one, and as they pass through the cross bar, M, are insulated from it, by a piece of ivory, inserted in the cross bar. The united wire then passes into and through the ivory hub, _e_, forming a perfect contact with the copper disc, _c_, underneath its socket, _n_: _d_, is a cup of mercury, in which the copper disc, _c_, is always immersed, and the needle, _b_, twice in every revolution of the armature. The cup, _d_, is so constructed as to rise and fall, by means of a stem, _i_, sliding vertically into a socket, _e_, of its support, and is secured to its position by the screw, _h_. In this way, its proper height for breaking and closing the circuit may be easily obtained, when the armature is rotating. The proper position for the needle, _b_, is that in which it is just leaving the mercury, as the keeper arrives at the position, in which its magnetism is neutralized. This position is seen at X, where D″ and D′ are the sides of the coils; _c_ the copper disc; _m_ the cross bar of the armature; R the arm passing through the coil; and _b_ the needle, at that _angle_ which it requires, when the armature is vertical or at its neutral position. It will be observed that the needle is just leaving the mercury, _d_.

Figure 44 represents a top view. N and S represent the north and south poles of the permanent magnet. N′ and N′ is the spindle, parallel with the prongs of the magnet, and equidistant from them; L is the socket of the band wheel; D′ and D the horizontal position of the coils; M is the cross bar; _b_ the needle; _c_ the copper disc, and _m_ and _n_ their respective sockets; _o_ the ivory hub; _d_ the cup of mercury; A the platform; and S′ and S′ the yoke through which pass two screws to secure the magnet to the wooden support below.

When the armature is made to rotate, it becomes a temporary magnet, by the laws of magnetic induction, whenever the arms carrying the helices come opposite to the poles of the permanent magnet, and when these soft iron arms have reached the point at _right angles_ to the _magnet_, or vertical, their magnetism for an instant is destroyed, and are as instantaneously reversed from what they were before reaching that point. They are also magnetic, just in that proportion as they recede from or approach to the poles of the permanent magnet.

Hence, first, _one arm_ is the south pole, when opposed to the north pole of the magnet; and the _other arm_ a north pole, when opposed to the south pole of the magnet. But when they have made a half revolution on their axis, from their first position, their magnetism is reversed. The arm which was a south pole, has become a north pole; and the arm that was a north pole has become a south pole. Thus, by the rotation of the armature, direction of the induced current in the arms, become changed, as often as they are alternately brought opposite the poles of the permanent magnet, which is _twice_ in every revolution of the armature.

It follows, then, by the laws of magneto induction, that as often as the arms become magnetic, they induce corresponding _opposite electric_ currents in the wire surrounding those arms, provided the circuit of the coils is complete. The disc, which is in metallic connection with two ends of the wire leaving the coils, (one from each coil,) is _always_ immersed in the mercury of the cup. The needle, however, which is in connection with the other two wires from the two coils, (one from each coil,) is _not always_ immersed, but only when the armature is at a certain position in relation to the permanent magnet. The circuit then can only be closed when the needle is immersed, as well as the disc. Upon inspecting the figure, it will be found that the needle is immersed at the time the arms are passing the poles of the magnet, and that when they arrive at the vertical or neutral position, the needle has just broken its connection with the mercury, and at that instant the spark is observed.

Professor Daniell observes, that “by means of this magneto electrical machine, all the well known effects of Voltaic currents may be very commodiously produced. When the communication is made between the spindle and the revolving disc, by means of a fine platinum wire, instead of the dipping points, the wire may be maintained at a red heat; although the effect being produced by alternating currents in opposite directions, a kind of pulsation, or intermission of the light, may be discerned. Upon making the communication between the two mercury cups, by means of copper cylinders _grasped_ in the _hands_, a continued painful contraction of the muscles of the arm takes place, which destroys voluntary motion, and, under certain circumstances, is perfectly _intolerable_.

“The general expression of these phenomena may be thus stated: whenever a piece of metal is passed, either before a single pole, or between the opposite poles of a magnet, or before electro magnetic poles, whether ferruginous or not, so as to cut the magnetic curves, (or lines, which would be marked out by a spontaneous arrangement of iron filings,) electrical currents are produced across the metal, transverse to the direction of motion.”

_Dr. Page’s Magneto Electric Machine._

This important instrument also depends, for its action, upon the principle discovered by Dr. Faraday, that electricity was developed in conducting bodies, when they were moved in a certain direction, in the neighbourhood of permanent magnets. Since the beautiful and ingenious invention which Mr. Saxton was the first to make, no valuable improvements have been made in this machine, except those introduced by Professor Page.

The first important change in the machine, was the adaptation of his pole changer to the machine, in place of the break pieces, which were used in all the modifications up to that time; and another equally useful improvement, consisted in the arrangement of the permanent magnets and armatures. Previous to this last improvement, these machines were constructed with a single permanent magnet, and one or more revolving armatures, necessarily involving great disadvantages. Page’s improvements were completed in February, 1838, and shortly after published in Silliman’s Journal. He was also the first to suggest the combination of several machines under one mechanical movement, as the best mode of augmenting power in this way.

_The combined machine, described in Daniell’s Introduction to Chemical Philosophy, as invented by Wheatstone, about two years since, is the same as that described, and represented by Dr. Page in Silliman’s Journal in 1838._ In the same publication, Dr. Page described the arrangement of the permanent magnets and armatures, as shown in the annexed figures. The adaptation of the pole changer, which, in connection with this machine, is called the _Unitrep_, Dr. Page has given to the public. But as he has never allowed the improvement, which consists in the use of two or more permanent magnets and straight armatures, to be sold with his knowledge and consent, he intends to claim a _patent for the same_; it having been decided by our courts, that the publication of an invention by the inventor, does not affect his right to a patent, provided he does not allow the invention to be sold and used.

The figures 45, 46 and 47, exhibit one of Page’s machines with his early improvements.

Figure 45, is a side elevation of the machine.

Figure 46, is a top view.

Figure 47, are views of the revolving armatures and coils.

In Figure 45, representing a side view of the machine, B and B are the compound permanent steel magnets, composed of six bars each of the U form, mounted upon the brass pillars, P, P, P, P, which are fastened into the common platform of the whole machine. Through the platform there pass stout rods, R and R, and upwards through two brass straps, above the magnets, B and B. These straps or yokes secure the magnets from any motion by means of the screw nuts. A is a circular case of pasteboard, containing the armatures and coils. H is a band wheel surrounding the case, for mechanical connection with any source of power that may be used to keep the machine in motion. I′ and I are two metallic studs, with an aperture passing vertically from the top, to the depth of an inch, for the reception of connecting wires, and then, by means of a screw at its side, to make a perfect contact. There are two other studs directly behind them. G and J are the two pulley wheels, with their band and crank, by which a rapid rotary motion is given to the armatures and coils. These pulleys are supported by the standard. From the bottom of the studs I′ and I, as also from those directly behind them, proceed wires which are carried along below the platform, and pass up through it between the pilliar, P, and the revolving armatures, to the shaft; there being one on each side of the axis.

Figure 46, represents a top view of the instrument. A is the case containing the armatures and coils, and H the band wheel. N, S and N, S, are the north and south poles of the permanent magnets. S′ and S′ are the yokes by which the magnets are secured to the platform, and the screws near the poles of the magnets are for the purpose of setting the magnets to any required position, laterally, and securing them in it. M and M are the tops of the two pilliars, which support the shaft of the armatures and coils. The bearings are so made as to allow the apparatus to revolve with as little friction as possible: 3 and 3 represent the set screws against the ends of the shaft, for adjusting the ends of the permanent magnets; by which means, the armatures may be allowed to pass very near the ends of the magnets without touching. 6, 7, 8, and 9 are the receiving studs, by which the wires from any other instrument may be connected with the machine. The wire, _a_, in contact with the unitrep, as before stated, is continued and soldered to the receiving stud, 6; in the same manner, _c_, also in contact with the unitrep, is connected with 7; and also 3 with 8; and _a_ with 9. The manner in which these wires, _a_, _c_, 3, and _a_, form their contact with the shaft, is seen at N and P, figure 45, of which 5 and 5 represent a section of the shaft and unitrep.

Figure 47 represents the revolving armatures and coils, with the case taken off. C and C are the two coils of insulated copper wire, surrounding two straight bars of soft iron, represented in the end view by D and D. E is the shaft. The two armatures and coils are secured to the two brass straps F, which are themselves fastened upon the shaft. The armatures are allowed to project through the straps about the sixteenth of an inch.

On each end of the shaft is attached an _unitrep_, consisting of two cylindrical segments of silver, as seen at 5 and 5, figure 45; insulated from each other, and secured to a cylinder of ivory or wood, upon the shaft, so as to revolve with it. The terminations of the coils of wire upon the armatures, are soldered to the segments of silver, and as the unitrep turns, it brings opposite ends of the wires, alternately, upon the stationary wires or conductors, P and N: (in figure 46 they are represented by _a_ and _c_, and 3 and _a_.) The opposing currents of the coils, in each half revolution, are, by this contrivance, made to form one continuous current. Hence, the name _unitrep_ (to turn together.) There being two unitreps, and corresponding conducting wires, and screw cups, the induced currents from the two coils may be combined in several ways, after the manner of combining separate batteries.

Let the wires below the base board be all properly connected with the receiving cups, as heretofore described. Then let the wire from 6, (represented by dots,) to _k_, be connected with the wire 9 and _m_; and also the wire 7 and _l_, with the wire 8 and 0. Let one of the united wires be connected with one wire leaving the coil of an electro magnet; and the other united wire be joined to the other wire of the electro magnet of the telegraph, or any other instrument designed to operate by a galvanic battery. When this preparation is finished, if the armatures and coils are made to revolve rapidly, a powerful current is formed in the induced coils, C and C, figure 47, capable of performing all the experiments generally made by means of the galvanic battery.

Dr. Page has made a very important discovery in connection with this machine, not now to be made known; but, suffice it to say, the single machine which he has now in his possession, on Christmas day, 1844, operated Morse’s telegraph, through the circuit of 80 miles; half this circuit being wire, the other half the earth. This machine makes an electro magnet sustain 1000 pounds, and melts a platinum wire one-fortieth of an inch in diameter.

_The Pole Changer._

We introduce here a description of an instrument used for reversing the direction of the galvanic current, and which is applied in the operation of several kinds of electric telegraphs. There is a variety of modes by which the same object is attained, but as this appears the most simple, we have chosen it in preference to others.

The following figures, 48, 49 and 50, are three views of the instrument as it appears when looking down upon it, in its three changes. First, that in which the current is broken and the needle vertical. Second, in which the circuit is closed and the needle deflected to the right. Third, in which the circuit is closed and the needle deflected to the left. Each figure has, in connection with the pole changer, the battery, or any other generator of the electric fluid, represented by N and P, and the galvanometer represented by G. In each of the figures, the circles numbered 1, 2, 3, 4, 5, 6, 7, and 8, represent cups, filled with mercury, let into the wood of the platform, and made permanent. The small parallel lines terminating in these cups, represent copper wires or conductors.

A, figure 48, represents a horizontal lever of wood, or some insulating substance, with its axis supported by two standards, B and C, by which it can easily vibrate. D represents an ivory ball, mounted upon a rod, inserted in the lever, and extending a few inches above it. It serves as a handle, by which to direct the elevation or depression of either end of the lever. Both ends of the lever branch out, presenting two arms each. Through each arm passes a copper wire, insulated from each other. The left hand branches support the wires which connect the mercury cups, 1 and 4, and 2 and 3, together. The right hand branches support the wires which connect the cups 5 and 7, and 6 and 8, together. The ends of these wires directly over the mercury cups are bent down, so that they may freely enter their respective vessels when required. The other wires are permanently secured to the platform. The position of the lever is now _horizontal_, and the bent ends of the wires, which it carries, are so adjusted, that none of them touch the mercury, consequently, there is no connection formed between the battery and galvanometer, and the needle is _vertical_. The ivory ball, it will be observed, is directly over the centre of the axis, and in that position required to break the circuit. Thus, the wires, 2 and 3, 1 and 4, 5 and 7, 6 and 8, are each out of the mercury, and the circuit being broken the fluid cannot pass.

Figure 49 represents those connections which are formed when the left hand side of the lever is depressed, immersing in the mercury those wires supported by it. The ball and lever are omitted for the better inspection of the wires. Now the circuit is closed, and the current is passing from P, of the battery, to the mercury cup, 1; then along the cross wire to 4; to 8; to the coils of the multiplier, deflecting the needle to the _right_; then to 7; to 3; then along the cross wire, (which is not in contact with wire 1 and 4,) to 2; to the N pole of the battery. The arrows also show the direction of the current. It will be observed that the cups 5 and 7, and 6 and 8 are not now in connection, and consequently the current cannot pass along the wires 1 and 5, and 2 and 6.

Now, if the ball, D, is carried to the right, a new set of wires, figure 50, are immersed, and those represented in figure 49, as in connection, are taken out of their cups. The fluid now passes from P, of the battery, to the mercury cup, 1; to 5; to 7; to the coils of the multiplier, deflecting the needle to the _left_; then it passes to cup 8; to 6; to 2; and then to the N pole of the battery; the arrows representing the direction of the current. It will now be found, that the cups, 2 and 3, and 1 and 4 are not in connection, and consequently the current cannot pass along the wires, 3 and 7, and 4 and 8.

Thus, it will appear, that by carrying the ball, D, to the left, the needle is deflected to the _right_; then, by carrying the ball to the right, the needle is deflected to the _left_; and that when the ball is brought to the vertical position, the needle is _vertical_. These three changes enter into the plans of several electric telegraphs, which are to be hereafter described.

_Professor Morse’s American Electro Magnetic Telegraph, invented, 1832._

To our readers the principles and arrangement of Morse’s telegraph have been fully explained in the former part of this work. We shall here present _some_ of the evidence of the time of its invention.

_Extract from a letter from S. F. B. Morse to the Hon. Levi Woodbury, Secretary of the Treasury, dated Sept. 27th, 1837._

“About five years ago, on my voyage home from Europe, the electrical experiment of Franklin, upon a wire some four miles in length, was casually recalled to my mind, in a conversation with one of the passengers, in which experiment it was ascertained that the electricity travelled through the whole circuit in a time not appreciable, but apparently instantaneous. _It immediately occurred to me, that if the presence of electricity could be made_ VISIBLE _in any desired part of this circuit, it would not be difficult to construct a_ SYSTEM OF SIGNS _by which intelligence could be instantaneously transmitted._ The thought, thus conceived, took strong hold of my mind, in the leisure which the voyage afforded, and I planned a system of signs and an apparatus to carry it into effect. I cast a species of type, which I had devised for this purpose, the first week after my arrival home; and although the rest of the machinery was planned, yet, from the pressure of unavailable duties, I was compelled to postpone my experiments, and was not able to test the whole plan until within a few weeks. The result has realized my most sanguine expectations.”

The following letters were published in the Journal of Commerce, from the originals now in possession of Prof. Morse.

_Letter of the Hon. W. C. Rives._

SENATE CHAMBER, _September 21st, 1837_.

MY DEAR SIR,—I hope you will find in my
multiplied and oppressive engagements here, an apology for
not having sooner answered your inquiry on the subject
of your Electro Magnetic Telegraph. I retain a distinct
recollection of your having explained to me the conception
of this ingenious invention, during our voyage from France
to the United States in the year 1832, and that it was, more
than once, the subject of conversation between us, in which
I suggested difficulties which you met and solved with great
promptitude and confidence.

I beg leave to assure you, that it would give us all
great pleasure to renew, in personal intercourse at home,
the agreeable souvenirs of our acquaintance, and friendly
relations abroad.
I remain with great respect,
Your most obd’t serv’t,
W. C. RIVES.

PROF. S. F. B. MORSE.

_Letter of Capt. William W. Pell,
of the packet ship Sully._

NEW YORK, _Sept. 27th, 1837_.

DEAR SIR—On my arrival here I received your
letter, calling upon my recollection for what was said on
the subject of an electric telegraph, during the passage
from Havre, on board of the ship Sully, in October, 1832.
I am happy to say, I have a distinct remembrance of your
suggesting, as a thought newly occurred to you, the
possibility of a telegraphic communication being effected
by electric wires. As the passage progressed, and your
idea developed itself, it became frequently a subject of
conversation. Difficulty after difficulty was suggested
as obstacles to its operation, which your ingenuity still
labored to remove, until your invention, passing from its
first crude state through different grades of improvement,
was, in seeming, matured to an available instrument, wanting
only patronage to perfect it, and call it into reality; and
I sincerely trust that circumstances may not deprive you
of the reward due to the invention, which, whatever be its
source in Europe, is with you at least, I am convinced,
original.

When you observed to me a few days before leaving the
ship, “_well, Captain, when you hear of the telegraph one
of these days, as the wonder of the world, remember the
discovery was made on board the good ship Sully_,” I, then,
little thought, I should ever be called upon to throw into
the scale, my mite of testimony in support of your claims
to priority of invention, for what seemed so startling a
novelty.
With my respects and best wishes,
I subscribe myself,
WILLIAM W. PELL.

SAMUEL F. B. MORSE, ESQ.

A subsequent letter from Captain Pell, dated February 1st, 1838, after having seen the operation of the telegraph at the University, has the following paragraph:

“When, a few days since, I examined your instrument, _I recognized in it the principles and mechanical arrangements_, which, on board, I had heard you so _frequently explain_ through all their developments.”

From a letter now in possession of the author, and addressed to him by Prof. Morse, we make the following extract:

“In 1826, the lectures, before the New York Atheneum, of Dr. J. F. Dana, who was my particular friend, gave to me the first knowledge ever possessed of electro magnetism; and some of the properties of the _electro magnet_; a knowledge which I made available in 1832 as the basis of my own plan of an electro telegraph. I claim to be the original suggestor and inventor of the electric magnetic telegraph, on the 19th of October, 1832, on board the packet ship Sully, on my voyage from France to the United States, and, _consequently_, the inventor of the first, really _practicable telegraph on the electric principle_. The plan then conceived and drawn out in all its essential characteristics, is the one now in successful operation. All the telegraphs in Europe, which are practicable, are based on a different principle, and, _without an exception_, were invented subsequently to mine.