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duced in the thin wire. Now this latter being completely ON PHYSICS, OR NATURAL PHILOSOPHY.
isolated, the induced current acquires so great a tension that No. LXX.
it is capable of producing very intense luminous effects. For
this purpose, the two ends of the fine wire, qy and px, which (Continued froin page 668.)
come out from beneath the glass plate, are connected with the
two rods attached to a globe m, such as has been already DYNAMICAL ELECTRICITY.
described under the title of the electrical egg, and is employed PHENOMENA OF INDUCTION.
to observe the luminous effects of an electrical machine in a
vacuum. Having produced a vacuum in the globe, a beautiful Effects of Tension produced by Currents of Induction.-M. Ruhm- luminous trail is produced from one end to the other, apparently korff has lately constructed some very powerful bobbins, by unbroken, and of the same intensity as is obtained with a means of which not only violent shocks may be produced by powerful electrical machine, the plate of which is turned currents of induction, but also luminous effects very strongly rapidly. resembling those of electrical machines of strong tension. It is the positive pole of the induced current which exhibits
This apparatus consists of a strong bobbin B (fig. 465), most brightness. Its light is red, while that of the negative placed vertically upon a thick plate of glass, which isolates it. pole is feeble and of a violet colour, and extends throughout The bobbin, which is about six inches high, is formed of two the whole length of the negative rod, a phenomenon which wires-one thick, about one-twelfth of an inch in diameter, does not take place at the positive pole. and making three hundred turns; the other fine, being only Messrs. Masson and Breguet made the first experiment to about an eightieth of an inch in diameter, and rolled round show that a bobbin of induction is capable of producing the the former ten thousand times. These wires are not only physiological effects of the Leyden jar; but it was M. Ruhmcovered with silk, but each coil is isolated from the next by a | korff who first, having completely isolated the induced current layer of gum-lac varnish. It is the thick wire which is the by means of the above bobbin, was enabled to obtain from it inductor. The current which passes through it is simply that electricity of any tension, and to produce effects of light such of a Bunsen battery. The positive pole of the battery being as have just been described. in connexion with the wire PH, the current passes through Stratification of Electric Light. --- In studying the electric the conductor ċ to a cylinder G; thence it descends by a light obtained from M. Ruhmkorff's bobbin of induction, metallic part 9, and reaches a copper plate F, which conducts M. Quet has lately observed, that if we do not produce a
it to one of the extremities v of the thick wire of the bobbin. vacuum in the globe m (fig. 466), till after having introduced The other end of the wire terminating at i, in one of the into it essence of turpentine, spirits of wine, etc., the appearcopper supports of the glass plate, the current, on leaving the ance of the light is completely altered. It then appears bobbin, proceeds to a second plate c, whence it ascends in an under the form of a series of zones, alternately bright and iron column us. There the current reaches an oscillating dark, forming a sort of pile of electric light between the two hammer a (fig. 466), which is sometimes in contact with a poles (fig. 467). conductor n, and sometimes separated from it. When contact In this experiment, it follows, from the discontinuity of the takes place, the current proceeds along the conductors n and current of induction, that the light is not continuous, but
(fig. 465), as shown by the arrows, ascends into the cylinder consists of a series of discharges nearer to each other, in pro4, and thence returns to the battery along the conductor a portion as the hammer a (fig. 466) oscillates more rapidly. and the wire Q,
The luminous zones then appear affected with a rapid doubleWith regard to the motion of the hammer a backwards and revolving and undulatory motion. M. Quet considers this for
wards, that is produced by a soft iron cylinder r o, placed motion as an optical illusion, because, if the hammer be made in the axis of the bobbin. When the current of the battery to oscillate slowly with the hand, the zones appear very dispasses along the thick wire of the bobbin, this iron is mag- tinct and fixed; but the phenomenon is then too instantaneous netised, and draws up the hammer a—which is also iron— to allow the undulations to be perceived, if there are any. from below. The current then being interrupted, since it The light of the positive pole is, as we have said, generally connot pass through the part n, the cylinder or loses its red, and that of the negative pole violet; but the colour magnetic properties, and the hammer a falls down again. At varies with the vapour or gas which is in the globe. this moment the current recommences, the hammer a is again M. Despretz has lately observed that the phenomena raised, and so on continually.
established by Messrs. Ruhmkorff and Quet with a disconAs the current of the battery passes thus interruptedly tinuous current may be produced with an ordinary continuous along the thick wire of the bobbin, at each interruption à current, but with this important difference, that the continuous current of induction, successively direct and inverse, is pro- I current requires a great number of Bungen couples, while the VOL. V
discontinuous current of M. Ruhmkorff's bobbin requires together in three points of view: the violence of the shock, only one. It is a remarkable fact, established by experiment, the magnitude of the deflection in the galvanometer, and the that the intensity of the effects of this bobbin increases very magnetising action upon steel bars. Thus examined, these little when the number of Bunsen couples is increased. currents exhibit very different results. They appear nearly
equal in respect of the deflection of the galvanometer
, while Fig. 467.
the shock of the direct current being very violent, that of the
, which enables us to convey communications to persons hundreds of miles off with all the rapidity of the lightning flash, whether they be in the same country or separated from us by miles of ocean waves. This achievement eclipses all the wonders accomplished by the application of steam, and is in
itself sufficient to render the present century for ever memorable The theory of the phenomena of the stratification of electric in the annals of our race. light in vapours, and the colouring of the poles, is not yet Electric telegraphs, we need scarcely say, are apparatus ascertaided satisfactorily.
which serve for the transmission of messages to great distances
, Characters of Currents of Induction. — From the various by means of voltaic currents along metallic wires. Eren last experiments upon currents of induction to which we have century, philosophers had entertained the idea of correspond. called the reader's attention, we see that, in spite of their ing at great distances by means of the effects produced by the instantaneous auration, they possess all the properties of electricity of electrical machines, and propagated along conordinary voltaic currents. Like them, they produce violent ducting wires. physiological, luminous, calorific, and chemical effects, and In 1814, Sammering invented a telegraph based upon the themselves give rise to fresh induced currents. Lastly, decomposition of water by the battery, which he employed u they deflect the needle of galvanometers and magnetise steel a means of indicating signals. In 1820, at a time when the bars, when they are passed along a copper wire wound round electro-magnet was not known, Ampère, guided by Ersted these bars in the form of a helix (fig. 452).
experiment, proposed to correspond by means of magnetised The shock of induced currents is much more intense than needles, above which a current was directed, employing us that of hydro-electric currents. The latter, indeed, do not many needles and as many wires as there are letters in the give any shock except with a large number of couples, while alphabet. In 1837, M. Steinheil, at Munich, and Professer a single Bunsen couple, with the bobbin, above described (figs. Wheatstone, in London, constructed telegraphs with severa 456 and 461), produces induced currents, the shock of which wires, each acting upon a magnetised needie, the source of the is insupportable and even dangerous when prolonged.
current being a Clarke's electro-magnetic apparatus, et The shock is entirely owing to the direct current, that is to hydro-electrical battery. But the telegraph could not be made say, to that which is produced when the current in the simple enough, till Professor Wheatstone, in 1840, introduced inducing wire is interrupted.
the use of electro-magnets. The intensity of the shock of induced currents renders their Without altering the principle of the electric telegraph
, its effects like that of electricity in a state of tension. However, form has been much changed; but all the forms may be as they always act upon the gadvanometer, it is probable that referred to three classes--the dial telegraph, the signal tele in the wires subjected to induction, there is electricity both in graph, and the writing telegraph. We proceed to give not a state of tension and in a dynamical state.
account of each of these varieties. The direct and inverse induced currents have been compared The Dial Telegraph. There are several sorts of dial telo
graphs. That which is represented in figs. 468 and 469 was mits it to a ratchet-wheel a, the axis of which carries the ir.di. constructed by M. Froment, and our drawings were made in cating needle or pointer. The teeth of the wheel are so bent June, 1850. M. Froment's telegraph is the same in principle that it is always moved in the same direction by the fork, as those employed on railways. Like them, it consists of two which is indispensable to the usefulness of the apparatus. distinct apparatus, one called the manipulator, for transmitting To understand the intermissions of the electro-magnet, we signals, and the other the receiver, for receiving signals. The have recourse to fig. 468. The wheel r has twenty-six teeth, former is connected with a carbon pile or battery Q, and the twenty-five of which correspond to letters of the alphabet, two apparatus are connected together by means of two metallic and the last to the interval reserved between the letters A and wires, either iron or copper, the former of which goes from Z. When, by holding the button p in the hard, you turn the
wheel R, the end of the piece n is, by its curvature, always in Fig. 469.
contact with the teeth. The piece m, on the contrary, has a cog at the end, cut in such a way that there is contact and interruption of contact in succession. Consequently, the communications with the battery being established, if you move forward the needle p four letters, for example, the current passes four times from a to n, and is interrupted four times. The electro-magnet of the distant station will therefore become attractive four times, and will cease to be so four times. Consequently, at last the wheel a will have turned four teeth, and as each tooth corresponds to a letter, the needle of the distant station will have gore over exactly the same number of letters as that at the station et departure. With regard to the part s, represented in both figures, it is a piece of copper moveable upon a tinge, and serving to interrupt the current or close it at will.
From what has been stated, it is easy to understand how correspondence is carried on from one place to another at a distance. Suppose, for example, the first apparatus (fig. 468) to be in London, and the second (fig. 469) at Birmingham, and the communication between the two stations being established by means of wires, we wish to transmit from London to Birmingham the word signal. The needles of the two apparatus being both at the interval between A and 2, the person who sends the despatch moves forward the needle p to the letter S,
where it stops for a very short time; the needle of the the starting point to the distant station, and the latter from apparatus at Birmingham, faithfully following the movements the distant station to the point of departure. Lastly, each of the needle in London, stops at the same letter, and then apparatus is furnished with a dial containing twenty-four the person who receives the despatch marks this letter. He letters, and a needle moveable upon the dial. It is the who is in London, continuing to turn the needle always in the experimenter's hand which moves the needle at the point of same direction, stops the needle at the letter I, and the other departure, but it is the electricity which turns that at the needle instantly stops at the same letter. Proceeding in the distant station.
same manner for the letters G N A L, the whole word is soon The following is the course of the current in the two appa- transmitted to Birmingham. ratus and the effects which it produces. From the battery it To call the attention of the person to whom we are about to proceeds along a copper wire A (fig. 468) to a piece of brass n make a communication, a bell is fitted up at the distant in contact with a metallic wheel R, passes into a second piece station, and is connected with the current whenever the corM, and then into the wire o, which joins the other station. respondence is suspended. A trigger, moved by the electroThere the current goes into the bobbin of an electro-magnet b, magnet, rings this bell directly the current passes, and thus concealed in fig. 469, but represented in profile in fig. 470, gives a signal that a message is about to be communicated.
Further, each station ought to be provided with the two Fig. 470.
apparatus above described (figs. 468 and 469), otherwise it will be impossible to return an answer.
We have supposed that the current which goes from London to Birmingham returns in the same way from Birmingham to London. But this second wire is useless. Experience has shown that, if the positive pole in London is connected with the apparatus, and the negative pole with the earth, it is sufficient for the conducting wire which goes to Birmingham to be there connected with the earth. It is generaly believed that the circuit is then closed by the earth through which the current returns from Birmingham to London. This hypothesis has been severely criticised by some philosophers, particularly by the Abbé Moigno, in his treatise on the electric telegraph. And indeed it is difficult to conceive that, on its arrival at Birmingham, the current, which by its nature tends to
disperse in all directions, should choose precisely that which which shows the hinder part of the apparatus. This electro- takes it back to the battery whence it started. M. Moigno magnet is fixed horizontally at one of its extremities, and by absorbs at the two ends of the wires the electricity which the
considers that the earth, acting in this case as a reservoir, the other it attracts a soft iron armature a, which forms part battery transmits, and the consequence is, that there is the of a bent lever moveable about its point of support o, while a coiled spring tends to move the lever in the contrary direction. same continuous current in the wire as if the two ends touched
each other. When the current passes, the electro-magnet attracts the lever a c, which, by means of a rod i, acts upon a second lever d fixed to a horizontal axis, which is itself attached to a fork F. When the current is interrupted, the spring r draws back the L'objet de la science est de connaître la vérité; son occupation, de lever a c, and with it all the parts of the apparatus depending la rechercher; son caractère, de l'aimer : les moyens de l'acquérir sont upon it,
The result of this is a motion backwards and de renoncer aux passions, de fuir la dissipation et l'oisiveté.-J.J forwards, which is communicated to the fork , which trans- ) Rousseau.
at least belongs to the “Vicar of Wakefield," a tale which, BI () GRAPH Y. No. XXI.
notwithstanding what critics have said, has become a favourite
with the civilised world. GO L D S M I T H.
Washington Irving, who published an edition of Goldsmith's
“ Miscellaneous Works," has written a charming sketch of his By J. R. BBARD, D.D.
life. The rich materials accumulated by Prior in his " Life di OLIVER GOLDSMITH is one of the few pets of literature. Oliver Goldsmith" (1837), have been wrought into an admi. Having failings and faults neither few nor small, he is always Oliver Goldsmith" (1848).' of neither the man nor the author
rable biography by Forster, in "The Life and Adventures el regarded with interest, and spoken of with pity rather than blame. If this charity resulted from gratitude for the instruc- can extracts give any adequate ideas. Yet we can only ask tion and pleasure conveyed in his writings, we should regard attention to what ensues. it as a sort of allowable offset paid by gratitude. But we fear the sentiment is allied to a toleration of the kind of errors of
THE VILLAGE INN. which Goldsmith was guilty, and which made the plague of his existence. Improvidence and moral infirmity are defects Near yonder thorn that lists its head on high, of character too serious to be glossed over even by qualities as Where once the sign-post caught the passing eye, amiable as the better points in Goldsmith's life. Perhaps the Low lies that house where nut-brown draughts inspired, existence of such goodness ought to make the moral censor Where gray-beard mirth and smiling toil retired ; the more rigid, because it is great excellence which those evil
Where village statesmen talked with looks profound, habits tarnish or almost destroy. Nor is it possible to think
And news much older than their ale went round;
Imagination fondly stoops to trace of the numerous and severe penalties which Goldsmith's faults
The parlour splendours of that festive place ; inflicted on him without combining detestation of the sin with
The white-washed wall, the nicely sanded floor, commiseration for the sinned. Amiable Goldsmith always The varnished clock that clicked behind the door ; was ; but for his want of forethought and moral fortitude, he The chest contrived a double debt to pay, would have been pre-eminently good and great.
A bed by night, a chest of drawers by day; Goldsmith, distinguished alike in prose and poetry, was The pictures placed for ornament and use, born on the 10th of November, 1728, in the county of Long- The twelve good rules, the royal game of goose : ford, Ireland, of whose sons, in their want of thrift and their The hearth, except when winter chilled the day, superabundance of buoyancy, he is no unfit representative.
With aspen boughs and flowers and fennel gay; His father, a clergyman, desirous that his son should follow
While broken tea-cups, wisely kept for show, his own profession, sent him to the university of Dublin, a
Ranged o'er the chimney, glistened in a row. relative bearing the cost (1745). A life of trouble began with
Vain, transitory splendour I could not all
Reprieve the tottering mansion from its fall? bickerings. Goldsmith fell out with his tutor, to whom he
Obscure it sinks, nor shall it more impart was reconciled by his brother. With a wandering disposition, An hour's importance to the poor man's heart. he bethought him of emigrating to America, but, destined to Thither no more the peasant shall repair, miss all his days, he missed his passage. He had no resource To sweet oblivion of his daily care ; but to return to the parental roof. Theology having been No more the farmer's news, the barber's tale, abandoned, he thence proceeded to Edinburgh in order to No more the woodman's ballad shall prevail; study medicine.
For the same purpose he repaired to the No more the smith his dusky brow shall clear, university of Leyden. The way back was not easy, for his Relax his ponderous strength and lean to hear : money was all spent. However he had a fute, and he could The host himself no longer shall be found
Careful to see the mantling bliss go round; play thereon. With this resource he passed through Flanders,
Nor the coy maid, half willing to be pressed, France and Germany into Switzerland, where he wrote a part
Shall kiss the cup to pass it to the rest. of his poem, "The Traveller.” In Geneva he had the good
Yes ! let the rich deride, the proud disdain, fortune to be made tutor to a young Englishman.
These simple blessings of the lowly train ; Leaving his pupil at Marseilles, he turned his steps to Padua, To me more dear, congenial to my heart, in whose university he graduated as doctor of medicine. In the One native charm, than all the gloss of art. year 1756 he returned to England, and under the pressure of Spontaneous joys, where nature has its play, want took an ushership in a school at Peckham, and then became The soul adopts, and owns their first-born sway, a druggist's assistant. 'At length, encouraged by a college Lightly they frolic o'er the vacant mind, friend, he offered his services as a physician in London. Unenvied, unmolested, unconfined. Without practice and without money, he connected himself
But the long pomp, the midnight masquerade,
With all the freaks of wanton wealth arrayed, with "The Monthly Review," and so began a literary career
In these, ere triflers half their wish obtain, out of which he was to gather an uncertain subsistence and an
The toiling pleasure sickens into pain; andying renown. He began his new mode of life with his
And even while fashion's brightest arts decos, “ Enquiry into the Present State of Taste and Literature in
The heart distrusting asks, if this be joy? Europe" (1759), a wide subject for a young man, and a dif- Ye friends to truth, ye statesmen who survey ticult one for an unpractised pen. Among other less con- The rich man's joys increase, the poor's decay, siderable compositions, he published in "The Public Ledger” his 'Tis yours to judge how wide the limits stand Chinese letters, under the title of “The Citizen of the World" Between a splendid and a happy land. (1762). About the same time he finished “The Traveller" Proud swells the tide with loads of freighted ore, (1765), which was followed by the "Letters on English History"
And shouting folly hails them from her shore; (1765), and his delightful Vicar of Wakefield,” (1766). The
Hoards even beyond the miser's wish abound,
And rich men flock from all the world around. next year appeared his first theatrical piece, « The Good.
Yet count our gains. This wealth is but a name, natured Man." Then came that sweet poem, "The Deserted
That leaves our useful product still the same. Village" (1770), as full of bad philosophy as it is of good senti.
Not so the loss. The man of wealth and pride ment. Very readable compilations, entitled, “A History of
Takes up a space that many poor supplied; England” (1772), a "Roman History,” a “ History of Greece,” Space for his lake, his parks extended bounds, and a “ History of the Earth and Animated Nature" (1774), Space for his horses, equipage, and hounds; were prepared for the booksellers. Meanwhile he had put The robe that wraps his limbs in silken cloth, forth (1773) his second and still popular play, “She stoops to Has robbed the neighbouring fields of ball their growth conquer" (alas ! poor Noll stooped but did not conquer ; how His seat, where solitary sports are seen, different the result, had he resolved to conquer without stoop. Indignant spurns the cottage from the green; ing!) These productions were a heavy tax on a frame never
Around the world each needful product flies, very robust. Yet more serious labours were in contemplation,
For all the luxuries the world supplies.
While thus the land adorned for pleasure all, He was engaged with the plan of a general Dictionary of Art
In barren splendour feebly waits the fall. and Science, when he was relieved from his load by the hand of
As some fair female, unadorned and plain, deaih (4th of April, 1774). The prize among his prose writings
Secure to please while youth confirms her reigu,