z7o A History of Electric Telegraphy
`
`As the result of all these observations the Bavarian
`philosopher concluded that " electrical combinations,
`when not exhibiting their electric tension, were in
`a magnetic state ; and that there existed a kind of
`electro-magnetic meridian depending on the electricity
`of the earth, and at right angles to the magnetic
`poles." • These speculations are, as we see, suffi-
`ciently obscure, and, like those that we have hitherto
`described, failed to throw any light on the relation so
`anxiously sought after.
`Nor can we give Oersted credit at this period for
`In a work which
`any more distinct apprehensions.
`
`It is curious to note that the
`• Phil. Mag., vol. lviii. p. 43.
`English philosophers entirely neglected this study, being content to
`follow the brilliant lead of Sir Humphry Davy in another branch
`Indeed, it seems to have been the general opinion
`of the science.
`in this country, as late as the year 1818, that there was nothing
`more to be discovered. Bostock, in his Account of Me History
`and Present State of Galvanism, published in London in that year,
`says :—
`"Although it may be somewhat hazardous to form predictions
`respecting the progress of science, I may remark that the impulse,
`which was given in the first instance by Galvani's original experiments,
`was revived by Volta's discovery of the pile, and was carried to the
`highest pitch by Sir H. Davy's application of it to chemical decom-
`position, seems to have, in a great measure, subsided.
`It may be
`conjectured that we have carried the power of the instrument to the
`utmost extent of which it admits ; and it does not appear that we are
`at present in the way of making any important additions to our know.
`ledge of its effects, or of obtaining any new light upon the theory of
`its action" (p. 102).
`Napoleon did not hold these views. In the First Consul's letter to
`the Minister, Chaptal, founding two prizes to encourage new researches
`in galvanism, he said :—" Galvanism, in my opinion, will lead to
`great discoveries."
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`27!
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`he published in German, in 1807, on the identity of
`chemical and electrical forces, he observes : *—
`" When a plate composed of several thin layers is
`electrified, and the layers afterwards separated, each
`is found to possess an electric polarity, just as each
`fragment of a magnet possesses a magnetic polarity.
`" There is, however, one fact which would appear to
`be opposed to the theory of the identity of magnetism
`and electricity. It is that electrified bodies act upon
`magnetic bodies, as if they [? the magnetic bodies]
`were endowed with no force in particular. It would be
`very interesting to science to explain away this diffi-
`culty ; but the present state of physics will not enable
`us to do so. It is, meanwhile, only a difficulty, and
`not a fact absolutely opposed to theory ; for we see in
`frictional electricity and in that of contact [galvanism]
`analogous phenomena. Thus, we can alter the tension
`of the electric pile by bringing near it an excited glass
`rod, and yet not affect in any way the chemical action.
`A long column of water, or a wetted thread of flax or
`wool, will also suffer a change in its electricity without
`experiencing any chemical changes.
`" It would appear, then, that the forces can be super-
`posed without interfering with each other when they
`operate under forms of different activities.
`" The form of galvanic activity holds a middle place
`between those of magnetism and [static] electricity.
`
`* Chap. viii. pp. 235-6 of the French edition, Recherches *fur
`Mental des Forces Chimigues d Eleariques, Paris, 1813.
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`272 A History of Electric Telegrafihy
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`The force is in that form more latent than as electricity,
`and less so than as magnetism. It is, therefore, pro-
`bable that the electric force, when superposed, will
`exercise a less influence on magnetism than on gal-
`vanism. In the galvanic pile, it is the electric state
`[tension] which it acquires that is affected by the
`approach of an excited glass rod ; more, it is not that
`interior distribution of forces constituting magnetism
`that we can change by electricity, but it is the electric
`state which belongs to the magnet as to bodies in
`general.
`" We do not pretend to decide anything in this
`matter ; we only wish to clear up, as far as possible, a
`very obscure subject, and, in a question of such im-
`portance, we shall be very well satisfied if we have
`made it apparent that the principal objection to the
`identity of the forces which produce electricity and
`magnetism is rather a difficulty of reconciling facts
`than of the facts themselves."
`And again, on p. 238, he says :—" Steel when
`heated loses its magnetism, showing that it becomes
`a better conductor by the elevation of temperature,
`like electrical bodies. Magnetism, too, like electricity,
`exists in all bodies in nature, as Bruckmann and
`Coulomb have shown. From this it seems that the
`magnetic force is as general as the electric ; and it
`remains to be seen whether electricity in its most
`latent state [1. e., as galvanism] will not affect the
`magnetic needle as such.
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`273
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`" This experiment will not be made without diffi-
`culty, for the electrical actions will blend and render
`In comparing
`the observations very complicated.
`the attractions on magnetic and non-magnetic bodies,
`some data will probably be obtained."
`In trying experiments with a view to the illustration
`of these hazy notions Oersted is said to have succeeded
`in obtaining indications of the action of the conducting
`wires of the pile, during the passage of electricity, on
`the needle ; but the phenomena were, at first view, not
`a little perplexing ; and it was not till after repeated
`investigation that, in the winter of 1819-2o, the real
`nature of the action was satisfactorily made out.*
`Even then Oersted seems not to have clearly under-
`stood the full significance of his own experiment.
`Unlike Davy, who, when he first saw the fiery drops
`of potassium flow under the action of his battery,
`recorded his triumph in a few glowing words in his
`laboratory journal,t Oersted took no immediate steps,
`
`• " Professor Forchhammer, the pupil and friend of Oersted, states
`that, in 1818 and 1819, it was well known in Copenhagen that he was
`engaged in a special study of the connection of magnetism and elec-
`tricity. Yet we must ascribe it to a happy impulse—the result, no
`doubt, of much anxious thought—that, at a private lecture to a few
`advanced students in the winter of 1819-20, he made the observation
`that a wire uniting the ends of a voltaic battery in a state of activity
`affected a magnet in its vicinity."—Ency. Brit., 8th ed., Dissertation vi.
`973.
`t On 16th October, 1807, while investigating the compound nature
`of the alkalies. On seeing the globules of potassium burst through the
`crust of the potash, and take fire as they entered the atmosphere, he
`could not contain his joy, but danced about the room in wild delight,
`T
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`274
`
`A History of Electric Telegraphy
`
`either to complete, or to publish, his discovery.
`" Although," he says, " the effect was unquestionable,
`it appeared to me, nevertheless, so confused that I
`deferred a minute examination of it to a period at
`which I hoped for more leisure." • And when he had
`made this minute examination and published the
`results, he could not explain the phenomena by a
`better hypothesis than that negative electricity acts
`only on the northern pole, and positive only on the
`southern pole of the needle.t
`This most important discovery may be thus briefly
`defined :—Supposing the electric current to pass from
`north to south through a wire, placed horizontally in
`the magnetic meridian, then a compass needle sus-
`pended above it will have its north end turned to-
`wards the west ; if below the wire, to the east ; if
`on the east side of it, the north end will be raised;
`and if on the west side, depressed. These results
`Oersted first published in a Latin tract, dated the
`21st July, 1820, a copy of which (with translation in
`English), will be found in the Journal of the Society
`of Telegraph Engineers, vol. v. pp. 459-69.
`
`and some time elapsed before he could sufficiently compose himself to
`continue his experiments.—Bakewell's Manual of Electricity, London,
`1857, p• 34.
`* Tyndall's Lectures on Voltaic Electricity at the Royal Institution,
`1876.
`t See concluding paragraph of his paper in the "'Puma/ of the Soc.
`of Tel. Engs., voL v, p. 468.
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`to the Year 1837.
`
`275
`
`CHAPTER X.
`
`ELECTRO-MAGNETISM AND MAGNETO-ELECTRICITY
`—HISTORY IN RELATION TO TELEGRAPHY
`(continued).
`
`THE effect of Oersted's pamphlet was most wonderful.
`The enthusiasm, says Lardner,* which had been
`lighted up by the great discovery of Volta twenty
`years before, and which time had moderated, was
`relumined, and the experimental resources of every
`cabinet and laboratory were brought to bear on the
`pursuit of the consequences of this new relation be-
`tween sciences so long suspected of closer ties. The
`inquiry was taken up, more particularly, by Ampere
`and Arago, in France ; by Davy, Faraday, Cumming,
`and Sturgeon, in England ; and by Seebeck, Schweig-
`ger, De la Rive, Henry, and numerous other philoso-
`phers in all parts of Europe and America.
`Among these, Ampere has assumed the first and
`highest place. No sooner was the fact discovered
`by Oersted made known, than that philosopher com-
`menced the beautiful series of researches which has
`lustre, and
`surrounded his name with so much
`
`* Elearieity, Magnetism, and Meteorology, vol. i. p. aos.
`T 2
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`276 A History of Electric Telegraphy
`
`brought electro-dynamics within the pale of mathe-
`matical physics. On the ath of September, 1820,
`within less than two months of the publication of
`Oersted's experiments, he communicated his first
`memoir on electro-magnetism to the Academy of
`Sciences.
`In this paper was explained the law which deter-
`mined the position of the magnetic needle in relation
`to the electric current.
`In order to illustrate this, he
`proposed that a man should imagine the current to
`be transmitted through his body, the positive pole
`being applied to his feet, and the negative pole to
`his head, so that the current shall pass upwards from
`the feet to the head. This being premised, a magnetic
`needle, freely supported on its centre of gravity, and
`placed before him, will throw itself at right angles to
`him ; the north pole pointing towards his left, and the
`south pole towards his right.
`If the person through whose body the current thus
`passes turn round, so as to present his face in different
`directions, a magnetic needle, still placed before him,
`will have its direction determined by the same con-
`dition ; the north pole pointing always to the left, and
`the south to the right.
`In the same memoir were described several instru-
`ments intended to be constructed ; especially spiral, or
`helical, wires, through which it was proposed to trans-
`mit the electric currents, and which, it was expected,
`would thereby acquire the properties of magnets, and
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`to the Year 1837.
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`277
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`retain these properties so long as the current might
`be transmitted through them. The author also ex-
`plained his theory of magnets, ascribing their attrac-
`tive and directive powers to currents of electricity
`circulating constantly round their molecules, in planes
`at right angles to the line joining their poles ; the
`position of the poles, on the one side or the other
`of these planes,• depending on the direction of the
`revolving current.
`While Ampere was proceeding with these researches,
`Arago directed his inquiries to the state of the wire
`through which the current was transmitted, so as to
`determine whether every part of its surface was en-
`dowed with the same magnetic properties. With
`this view, he placed iron filings around the wire, and
`found that they adhered to it so long as the current
`flowed, and fell away immediately the connection
`with the battery was broken. He also found that
`on placing small steel needles across the wire
`through which a current from a voltaic pile, or a
`discharge film a Leyden jar, was sent, they were
`attracted, and, on removal, were found to be perma-
`nently magnetised. Acting upon Ampere's theory
`of magnetism, he placed in a glass tube an ordinary
`sewing needle, and wound round the tube a copper
`wire. On sending a current through this wire the
`needle was magnetised, its polarity depending on the
`
`* Annaks de Chinsie el de Physique, Paris, i8ao, vol. xv. pp. 59
`and 17o.
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`278 A History of Electric Telegraphy
`
`direction of the current.
`If the helix were right-
`handed, the north pole was found at the end at which
`the current entered ; and if left-handed, the same
`end was a south pole. In the same way he was
`able to impart a temporary magnetism to soft iron
`wires.•
`Another important discovery, which followed fast
`on the heels of Oersted's experiments, was that of
`Schweigger, of Halle, announced on the 26th Sep-
`tember, 1820. Observing that the deflection pro-
`duced by the outward current of a battery flowing
`over the needle was the same as that of the return
`current under the needle, he made the wire pro-
`ceed from and to his battery above and beneath
`the needle, and obtained, as he expected, twice
`the effect ; by giving the wire another turn round
`the needle the effect was again doubled ; a third
`turn produced six times the original deviation ; a
`fourth, eight times, and so on. This effect may be
`thus formulated : — If a magnetised needle, free to
`move, be surrounded by a number of convolutions
`of insulated wire, the power of the current to deflect
`it will increase in proportion to the number of con-
`* Amsak: de Chimie et de Physique, vol. xv. p. 93. Soon after,
`and before any knowledge of Arago's experiments had reached England,
`Davy also succeeded in magnetising needles by the voltaic current, as
`well as by ordinary frictional electricity, and showed the effect of the
`conducting wire on iron filings. See his letter to Wollaston, dated
`November 123 1820, in the Phil. Trans., for am. About the same
`time Seebeck communicated n paper to the Berlin Academy on the
`same subject.
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`to the Year 1837.
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`279
`
`volutions.* In this way the effect of a very feeble
`current may be so multiplied as to produce as great
`a deviation of the magnetic needle as would other-
`wise be produced by a very strong current.
`On this principle are constructed instruments for
`indicating and measuring currents of electricity, called
`electro-magnetic multipliers, or, more commonly, gal-
`vanometers t—the former being the name originally
`given to the arrangement by Schweigger. His first
`contrivance was a very humble affair, consisting of a
`small compass-box, round which were coiled several
`turns of copper wire in a direction parallel to the
`meridian line of the card.4 Yet this was the pro-
`totype of the beautiful instruments of Du Bois-
`Reymond and Sir William Thomson, in the former
`
`• The practical reader is, of course, aware that this definition is not
`strictly true,—for three reasons : 1st, as the convolutions increase, the
`strength of the current decreases, by reason of the increased resistance
`in the circuit ; 2nd, each convolution has less and less effect, as it is
`farther and farther removed from the needle ; and, 3rd, the current
`exerts less and less force on the needle, as it is deflected farther and
`farther from the plane of the current.
`In the early part of the century this name was applied to measuring
`instruments based on the chemical and calorific properties of the cur-
`rent ; but these are now denominated voltameters, and the name
`galvanometer is reserved exclusively for the class of apparatus described
`in the text.
`Schweigger's 7mensal jar Chemie and Physic, vol xxxi. pp. 1-t7.
`A galvanometer of different form, called a gahmno-maputie conden-
`sator, with vertical coils and unmagnetised needle, was shortly after,
`but independently, devised by the celebrated Poggendorff, then a
`student at Berlin. As the published description of his apparatus pre-
`ceded that of Schweigger's, he is sometimes regarded as the first
`inventor (Gilbert's Annals der Phyrik, voL lxvii. pp. 422-29).
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`2 8o A History of Electric Telegraphy
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`of which as many as 30,000 convolutions are some-
`times employed.
`There was, however, still wanting another discovery
`to bring the galvanometer to its present perfection,
`and this want was soon supplied. In deflecting a
`magnetic needle the current acts against the direc-
`tive force of terrestrial magnetism ; hence it is clear
`that if this force could be neutralised the deflection
`would be greater ; in other words, a galvanometer, in
`which the needle is freed from the controlling action
`of the earth's magnetism, would be more sensitive
`than the same galvanometer when its needle was
`not so freed. Ampere suspended a single needle
`so that the earth's magnetism acted perpendicularly
`to it, and had, therefore, no directive force upon it ;
`and he found that it set accurately at right angles to
`the current.
`This led him to the invention of the double, or
`astatic, needles, which he thus describes in his memoir
`of 1821 :
`" When a magnetic needle is withdrawn from the
`directive action of the earth, it sets itself, by the
`action of a voltaic conductor, in a direction which
`makes a right angle with the direction of the con-
`ductor, and has its south pole to the left of the
`current against which it is placed ; so that if M.
`Oersted, in the experiments which he published in
`1820, only obtained deviations of the needle which
`were less than a right angle, on placing it above or
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`to the Year 1837.
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`2 8 I
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`below a conducting wire parallel to its direction, it
`was solely because the needle which he subjected to
`the action of the current was not withdrawn from that
`of the earth, and took consequently an intermediate
`position between the directions which the two forces
`tended to give it. There are several means of with-
`drawing a magnetic needle from the earth's action.
`A very simple one consists in attaching to a stout
`brass wire, which has its upper part curved and fitted
`with a steel point of suspension, two magnetic needles
`of equal strength, in such a manner that their poles
`are in opposite directions, so that the directive force
`of the earth upon one is destroyed by the action in
`the opposite direction which it exercises on the other.
`The needles are so arranged that the lower one is just
`below the conducting wires, and the upper one close
`above them. On sending a current through the con-
`volutions the needles turn, until they take a direction
`at right angles with the conducting wire." •
`Having oscillated a magnetised needle, freely sus-
`pended in a circular copper cage, the bottom and sides
`
`* Annak: de Chimie d de Physique, vol. xviii. p. 32o. In Professor
`Cumming's paper On the connection of Galvanism and Magnetism,
`read before the Cambridge Philosophical Society on April 2, 1821, he
`described a near approach to the astatic needle. In order to neutralise
`the terrestrial magnetism he placed a small magnetised needle under
`the galvanometer needle.—Trans. Cam. Phil. Soc., vol. i. p. 279.
`The credit of Ampere's discovery is usually attributed to Nobili. As
`In Noad's Manual of Electricity, London, 1859, p. 327; also Roget's
`Ekaro-Magnetism, in Library of Useful Knowledge, London, 1832,
`p. 42.
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`282 A History of Electric Telegraphy
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`of which were very near the needle, Arago, in 1824,
`noticed that the oscillations rapidly diminished in
`extent, and very quickly ceased, as if the medium in
`which they were being produced had become more
`and more resistant. The proximity of the copper,
`while thus checking the amplitude of the oscillations,
`was observed to have no effect on their duration, they
`being accomplished in exactly the same time as in
`free air. By making the needle oscillate at different
`distances above discs of different materials, Arago
`found that distance considerably diminished the effect ;
`and that metals acted with more energy than wood,
`glass, &c.•
`Arago now conceived the idea of trying whether the
`disc which possessed this remarkable property would
`not draw the needle with it if itself rotated. The
`experiment was tried and resulted in the discovery of
`a new class of phenomena to which its author gave the
`name of magnetism by rotation. If we fix to a rotation
`apparatus, such as a table made for experiments on
`centrifugal force, a copper disc, about twelve inches
`diameter, and one-tenth inch thick, and just above it
`suspend, by a silk fibre, a magnetic needle, in such a
`manner that its point of suspension is exactly above
`the centre of the disc (care being taken to interpose a
`
`* Annales de Chin:. d de Physique, voL xxvii. p. 363. Seebeck, of
`Berlin, on repeating these experiments two years later, obtained analo-
`gous results. See Fogg. Ann., vol. vii. We shall see further on, pp. 32r,
`and 336-7, the use that has been made of this fact in the telegraphs of
`Gauss and Weber, and SteinheiL
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`283
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`screen of glass or paper, so that the agitation of the
`air resulting from the motion impressed upon the disc
`may have no effect upon the needle), and then put the
`disc in rotation, the needle is seen to deviate in the
`direction of this rotation, and to make with the mag-
`netic meridian a greater or less angle according to
`the velocity with which the disc is revolved. If this
`movement be very rapid, the needle is deflected more
`and more, until finally it rotates with the disc.
`The effect diminishes very rapidly with the distance
`of the needle from the disc ; and is still further lessened
`by cutting slits in the latter in the direction of rays—
`a fact which, as our practical readers know, is of the
`highest importance in the construction of electro-
`magnets.
`Whilst Arago was analysing the force that he had
`discovered, Babbage and Herschel, Barlow, Harris,*
`and others, undertook an investigation of the causes
`that may vary its intensity. Messrs. Babbage and
`Herschel repeated Arago's experiment by inverting it.
`They found that discs of copper, or other substances,
`when freely suspended over a rotating horse-shoe
`magnet, turned in the same direction as the magnet,
`with a movement at first slow, but which gradually
`increased in rapidity. The interposition of plates of
`glass and of non-magnetic metallic bodies in no degree
`
`* For researches of the three first-named philosophers, see Philo-
`sophical 7'ratuactions, for 1825 ; for those of Sir W. Snow Harris, see
`same for 1831.
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`284 A History of Electric Telegrafihy
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`affected the results ; but it was not the same with
`plates of iron. The action was then greatly reduced,
`or even entirely annihilated.
`These two philosophers confirmed the accuracy of
`Arago's observations on the influence of solutions of
`continuity, either partial or total, in the discs subjected
`to experiment. Thus, a light disc of copper, suspended
`at a given distance above a magnet, executed its (6)
`revolutions in 55". When cut in eight places, in the
`direction of radii near the centre, it required 121" to
`execute the same number ; but, on the parts cut out
`being again soldered in with tin, the original effect
`was almost attained, the disc performing its revolu-
`tions in 57". The same effects were obtained with
`other metals.
`Sir W. Snow Harris, who made a great number of
`experiments on this subject, not only found great
`differences between bodies with regard to their power
`of drawing the needle after them when rotating, but
`also with regard to the property they possess of inter-
`cepting this action. He observed that iron, and mag-
`netic substances generally, are not the only ones that
`are thus able to arrest the effect of magnetism by
`rotation. Plates of non-magnetic substances, such as
`copper, silver, zinc, will do the same, provided only
`they be sufficiently thick, as from three to five inches.
`From a study of all these experiments Christie
`deduced the law that the force with which different
`substances draw along the magnetic needle in their
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`to the Year 1837.
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`rotatory movement is proportional to their conducting
`power for electricity. But a full explanation of these
`phenomena could not be given until after Faraday's
`discoveries in 1831, when it was seen that they were,
`one and all, the result of the electric currents induced
`in the disc by its rotation in the field of the magnet.
`In the case of those discs in which slits, or rays, were
`cut, the free circulation of these currents was pre-
`vented, and, consequently, there was no effect on the
`needle.*
`In November 1825, a great advance was made on
`Arago's experiment of magnetising soft iron, by the
`invention of the electro-magnet—an instrument which,
`in one form or another, has become the basis of nearly
`every system of electric telegraphy. We owe this
`most important contrivance to Sturgeon, a well-known
`electrician of Woolwich, who had worked in his earlier
`days at the cobbler's last,t as Franklin had done at the
`printing stick, and Faraday at bookbinding. Fig. Ica
`shows the earliest form of the instrument—a piece of
`stout iron wire, bent into the form of a horse-shoe,
`
`* See Faraday's Experimental Researches, 1831; also Henry's clas-
`sical paper on Elatro-dynamic Induction, in Trans. Amer. Phil
`Soddy, for 1839, vol. vi. p. 318.
`t He was apprenticed to a shoemaker, and disliking the employ-
`ment, at the age of nineteen entered the Westmoreland Militia, and
`two years later enlisted in the Royal Artillery. While in this corps
`he devoted his leisure to scientific studies, and made himself familiar
`with all the great facts of electricity and magnetism, which were then
`opening on the world. His subsequent career has created for him an
`undying name in the annals of electricity.
`
`Digitized by Coos I r
`Comcast - Exhibit 1014, page 316
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`Comcast - Exhibit 1014, page 316
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`

`286 A History of Electric Telegraphy
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`coated with an insulating varnish, and then bound
`round loosely with bare copper wire, the turns (of which
`there were sixteen) being, of course, separated from
`each other. This electro-magnet, when excited by a
`
`FIG. 10.
`
`single voltaic pair of large (13o square inches) surface,
`was capable of supporting a weight of nine pounds, a
`wonderful performance in those days.*
`Some of the further steps in the perfection of the
`electro-magnet as used in telegraphy were made by
`Professor Henry in America, between the years 1828
`and 1831, and it will be interesting to retrace them
`here, if only to see how little learned professors, fifty
`years ago, understood the conditions underlying the
`conversion of voltaic into magnetic force, and conse-
`quently how much groping in the dark, and stumbling
`to conclusions, where now Ohm's celebrated law makes
`everything so clear.
`Henry was led to his first improvements in electro-
`magnets by a study of Schweigger's galvanometer,
`
`* Transactions Society of Arts, 1825, vol. zliii. pp. 38-52.
`
`Digiti2b6nC
`
`(aI
`
`.- Exhibit 1014, page 317
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`Comcast - Exhibit 1014, page 317
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`

`to the Year 1837.
`
`287
`
`which resulted in the idea that a much nearer approxi-
`mation to the requirements of Ampere's theory could
`be attained by insulating the conducting wire itself,
`instead of the rod to be magnetised, and by covering
`the whole surface of the iron with a series of coils in
`close contact.
`In June 1828, he exhibited at the Albany Institute
`of New York, of which he was then professor, his
`electro-magnet, constructed on this principle. It con-
`sisted of a piece of soft iron, bent in the form of a
`horse-shoe, and closely wound with silk-covered copper
`wire, one-thirtieth of an inch in diameter.
`In this
`way he was able to employ a much larger number of
`convolutions, while each turn was more nearly at
`right angles with the magnetic axis of the bar. The
`lifting power of this magnet was, conformably to
`Henry's anticipations, much greater, ceteris paribus,
`than that of Sturgeon.
`In March 1829, he exhibited, at the same place, a
`somewhat larger magnet of the same character. A
`round piece of iron, about one quarter inch diameter,
`was bent into the usual horse-shoe form, and tightly
`wound with thirty-five feet of silk-covered wire, in
`about four hundred turns, with silk ribbon between.
`A pair of small battery plates, which could be dipped
`into a tumbler of dilute acid, were soldered, one to
`each end of the wire, and the whole mounted on a
`stand. With this small battery the magnet could be
`much more powerfully excited than another of the
`
`D' IntiirrfC2s(egLexhibit 1014, page 318
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`Comcast - Exhibit 1014, page 318
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`

`288 A History of Electric Telegrathy
`
`same sized core, wound according to the method of
`Sturgeon and excited by a battery of twenty-eight
`plates of copper and zinc, each plate eight inches
`square.•
`" In the arrangement," says Henry, "of Arago and
`Sturgeon, the several turns of wire were not precisely
`at right angles to the axis of the rod, as they should
`be to produce the effect required by the theory, but
`slightly oblique, and, therefore, each tended to develop
`a separate magnetism not coincident with the axis of
`the bar. But in winding the wire over itself, the
`obliquity of the several turns compensated each other,
`and the resultant action was at the required right
`angles. The arrangement, then, introduced by myself
`was superior to those of Arago and Sturgeon, first, in
`the greater multiplicity of turns of wire, and second,
`in the better application of these turns to the develop-
`ment of magnetism.t
`"The maximum effect, however, with this arrange-
`ment and a single battery was not yet obtained.
`After a certain length of wire had been coiled upon
`the iron, the power diminished with a further increase
`of the number of turns. This was due to the increased
`resistance which the longer wire offered to the con-
`
`* Smithsonian Report, z878, p. 282.
`t " When this conception," said Henry, "came into my brain, I
`was so pleased wjth it that I could not help rising to my feet and
`It was his first disco►ery. See
`giving it my hearty approbation."
`Professor Mayer's Eulogy of Henry, before the American Association
`for the Advancement of Science, z880.
`
`' 1''''zCovnQ6YSLexhibit 1014, page 319
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`Comcast - Exhibit 1014, page 319
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`

`

`to the Year 1837.
`
`289
`
`duction of electricity. Two methods of improvement,
`therefore, suggested themselves. The first consisted,
`not in increasing the length of the coil, but in using a
`number of separate coils on the same piece of iron.
`By this arrangement the resistance to the conduction
`of the electricity was diminished, and a greater quan-
`tity made to circulate around the iron from the same
`battery. The second method of producing a similar
`result consisted in increasing the number of elements
`of the battery, or, in other words, the projectile force
`of the electricity, which enabled it to pass through an
`increased number of turns of wire, and thus to develop
`the maximum power of the iron." *
`Employing a horse-shoe, formed from a cylindrical
`bar of iron, half an inch in diam