ALLAN'S NEK DLL TELEGRAPH—DERIXG’S ELECTRIC TELEGRAPH.
r Class X.
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remaining at rest for the remainder of the twenty-fourhours, ready for use and in good working order whenrequired. During this time of inactivity there is a continu-ous slow action between the diluted acid and the copper,whence is produced sulphate of copper, which in its turnbecomes decomposed, and the copper released upon thezinc, induces local action, greatly reducing the power ofthe battery and destroying the zinc, so that it requires tobe changed and cleansed more frequently than wouldotherwise be the case. To obviate this, Mr. Walkersought for a substance that might possess the good pro-perties of the copper-plate, but which should not be actedupon by the acid. The corrosion deposited on the inte-rior of old gas retorts is admirably adapted for thispurpose, and he has had it cut into plates by circularsaws, uorked by steam machinery. He has preservedthe history of a 12-plate battery, which was connectedup to do telegraph duty, where the waiting-time wasvery great as compared with the working-time. It wascharged in the usual way, with diluted sulphuric acid, onApril 5, 1849, and remained efficient till the middle ofFebruary, 1851, without having been washed or havinghad the sand changed. It was supplied with about adessert-spoonful of acid water twenty-one times duringthe above period of ninety-seven weeks, and six timeswith merely warm water. It suffered most from mereevaporation; in some cases it did duty for thirty-four,thirty-nine, and forty days, and in one instance forseventy-seven days, without having been touched. OnSeptember 15, 1851, it was dusted and had a little acidwater poured in, when it still gave a feeble -workingcurrent.
VII. Moveable Studs .—This is a very simple arrange-ment, and originated with Mr. Walker. The motion ofthe telegraph needle is limited within a certain angle bytwo small ivory studs. In the year 1848 there were somany magnetic storms and other abnormal conditions,that the needles were very frequently deflected ineither direction, and often hard up to the studs, sothat the power of deflecting in that direction for thepurpose of signalling was lost, the needle being alreadythere, and thus the telegraph was rendered nearlyuseless; indeed, quite so in the hands of inexperiencedclerks. To remedy this, Mr. Walker has mounted thestuds on a circular and moveable disc, so that in propor-tion as the needle is deflected abnormally, the studs maybe moved after it by the motion of this disc, and theneedle, though not hanging vertical, may still maintainits position of equilibrium midway between the studs.This contrivance works well, and the Telegraph Com-pany have adopted it.
VIII. Maying Handle .—This is used at stations wherethe bell has a distinct wire to itself. It enables an inter-mediate station to send the electric force in the directiononly of the station whose attention it is required to call.This improvement is Mr. Walker’s, as are also the essen-tial details of the apparatus; before the introduction ofwhich it was found difficult to keep the circuit good.The line wires are cut between the ringing key and thebell, and strong springs are inserted, which press onbrass studs and keep good the circuit when the apparatusis in a state of rest. To the handle is attached a move-able cylinder, furnished with two strong studs in properconnection with the respective poles of the battery. Bymoving the handle, one of these studs, and consequentlyone poie of the battery is put in connection with a strongbrass boss, connected by a wire with the earth, and theother stud, according as the handle is moved to the rightor to the left, raises the spring on either side the bell,and sends the current up or down the line, as the casemay be. This arrangement is used throughout theSouth-Eastern Company’s lines, and works well.
A Prize Medal was awarded to Mr. Walker.
Allan’s Patent (No. 201, p. 431) consists of a circulardial plate, arranged in a sloping position, with an alpha-bet and a pointer, which by a handle is brought round tothe letter required; at the same time it makes, breaks,and reverses the current. By this means the pointerson the second or telegraph dials are made to indicate thesame letter at distant stations.
The chief feature is the form and disposal of themany-poled permanent magnet which works the ratchet-ulieel arrangement, thereby giving motion to the pointeror index of the telegraph. The power in this instanceis created by two electro-magnets, having their polesprojecting between the arms of the many-poied permanentmagnet, each pair of arms being so magnetized asto act collectively in conjunction with the poles of thetemporary magnets; by this means the frame actingupon the ratchet-wheel is made to alternate in co-incidence with the changing of the current, and so causethe axis of the index-hand to rotate.
To impart a rapid movement to the index-hand, thecurrent changer is formed of three metallic discs, insu-lated from each other, and so arranged as to the numberof letters on the dial-plate, that the current is made,broken, and reversed accordingly, and causing theindex-hand to pass round at once to the letter required,with great rapidity.
Allan’s needle telegraph consists of four electric cy-linder coils, placed between the arms of a many-poledmagnet of four pair of arms; each arm of each pair ismagnetized so as to possess the same polarity ; thuswhen the current passes through the coils, the com-bined magnet is attracted or repelled in either direction,according to the movement of the current, thereby givingdeflection to a needle with great rapidity and precision.
The system developed by these improvements consistsin forming magnets out of one piece of steel, with anynumber of poles required, and placing cylinder-coils, orelectro-magnets, between the poles, thereby not only ob-taining a much greater amount of magnetic powerwithina small compass, but also a greatly diminished resistanceto the electric current: as each turn of wire in each coilis so placed that the current passing is within effectiveinfluence of a magnetic pole, none is lost, whilst thelength of wire, and consequent resistance is greatly re-duced; the action, too, being direct, likewise preventsthe loss or waste of the current power.
The great advantages gained by these combinationsare shown by the fact of there being surplus power suffi-cient to overcome the friction of the ratchet-wheelarrangement, without the assistance of weights ormachinery, also with as little battery power as thecommon needle telegraph now in use.
A Prize Medal was awarded to Mr. Allan*.
Dkrixg (No. 436, p. 460) has exhibited an electric-telegraph. Mr. Dering suspends his indicating magnet(which is deflected) not by the simple action of thecurrent, but by coil-maguets on either side, so as tohave its centre of gravity below the points of suspension :either by elastic bands, by the attraction of a permanentmagnet, or by such an adjustment of a straight bar, or pairof watch-springs, as shall give it a decided tendency toa vertical position when not under lateral influence.
Mr. Dering lias also exhibited an apparatus for convey-ing secret signals without extra wires ; viz., signals whichshall be read off only at given localities without passingalong the whole line included in the primary wire. Thishe lias accomplished by placing at each station a step-by-step revolving disc, included in the primary line of wire,but so arranged as not to be set in rotation except by agalvanic force greatly superior to that which makes theordinary signals, or, when only currents in one direction arcused for these signals, then, by the reverse current. Thisdisc, being brought at every station to correspondence inpoint of position with its position at the initial station, ismade by a system of non-conducting interruptions to thecontinuity of its circumference to establish a break, ac-cording to its position, cross connections, or short cuts bywhich the signal current can pass (and therefore willpass) from one point to another of the primary line ofwire, without running through the length of wire con-stituting the local working coil of the station, sothat the working of the telegraph at that station istemporarily suspended, the electricity finding for a timea shorter and easier passage. Besides this ingenious con-trivance, Mr. Deling has exhibited modes of preventingthe disturbing action of atmospheric electricity and thedestructive effects of lightning.