AUSTRIAN CIRCUIT CLOSER, MERCURY CIRCUIT CLOSER.Plate XIV
AUSTRIAN CIRCUIT CLOSER, MERCURY CIRCUIT CLOSER.
The armhis close to, but insulated from a metal platen, which latter is permanently connected with the conducting wire leading from the firing battery, and thus while in a state of rest is electrically charged; beyond the armiis a springo, which is connected with the earth, and in such a position that when the central portion is moved round, this springocomes in contact with the armi, and the platenwith the armhsimultaneously, and the circuit is thus completed through earth to the battery, but the current of electricity does not pass through the fuze. The armsk,lon the opposite sidesof the cylinder, and consequently insulated one from the other, are connected with the fuze, and the armmis connected with the earth.
On a further pressure of the vessel on the buffer, the armiis pushed beyond the spring, and in contact therewith, and consequently the circuit by earth to the battery is broken, while the contact of the armhand platenis still retained, and the current is passed by the armkthrough the fuze to the arml, and then to earth through the armm, thus completing the electric circuit of the firing battery through the fuze, and to exploding the mine.
The spring acts as a circuit breaker, and by means of an intensity coil in connection with the firing battery, the current is only passed through the fuze when at the point of greatest intensity.
By detaching the firing battery, the channel defended by such submarine mines may be rendered safe.
Fuze only in Circuit at Moment of Firing it.—One of the principal objects to be gained by the employment of such an arrangement for the closing of the electric circuit in connection with submarine mines, is the prevention of premature explosion from induction which might be caused by the proximity of any atmospheric electricity, the fuze in this system being entirely cut out of circuit until the moment when it is necessary to fire it.
The Austrians employed this form of circuit closing instrument during the war of 1866, and still continue to use it in connection with their coast defence by submarine mines.
McEvoy's Mercury Circuit Closer.—AtFig. 59is represented a longitudinal section of a circuit closer of this construction.
It is placed in the mine in such a manner that when undisturbed it maintains an approximately upright position.
It consists of a metal tubeainto which the cupbof vulcanite, or other insulating material is fixed. The cup is contracted at some distance from the top by the perforated plugc, which is also of insulating material;dis a metal pin fixed into the bottom of the cupb, it is connected with the wiree, which is insulated and passes to the battery;fis a metal plug closing the tubeaand the cupbat the top;gis a wire attached to the plugf, and passing from it to an earth connection. The cupbis filled with mercury up to the level of the plugc. By the contact of a passing vessel the instrument would be tilted sufficiently to cause the mercury to flow into contact withthe metal plugf, thus completing the electric circuit and exploding the mine.
This form of circuit closer, though not generally adopted, would, on account of its being less liable to derangement by the motion of the waves, or by the explosion of an adjacent or counter mine, seem to fulfil the many requirements of a circuit closer for general service.
McEvoy's Weight Magneto Circuit Closer.—This form of circuit closer, which is shown in section and plan atFig. 60and61, is one of the most important improvements that has ever been effected in such apparatus, and bids fair to become universally adopted.
A heavy metal conical shaped weighta(Fig. 60), hollowed out in its base and working in a ball and socket jointb, rests on a solid brass basec, and is so arranged that on the apparatus being struck, the weightawill fall over, pivoting on one of its supportsd,d;eis a band of india rubber, encircling the weighta, for the purpose of preventing a jar on its falling against the sides of the brass cylinderf, which contains the weightaand jointb. A brass rodg, connected to the ball and socket joint, passes through the basec, through a strong spiral springh(which latter rests on an adjusting screwk), through a piece of ebonitel, which supports the bobbins and corem,m1; then between these bobbinsm,m1through an armaturen, which is pivoted atp; and lastly through a slight spiral springo, which is kept in position by the adjusting screwi.
The armaturenis fitted with a small piece of brassr, so arranged that when it (the armature) is in the position shown inFig. 60, this piece of brassrdoes not make contact with the two strips of metal,s,s, between which it,r, works; but when the armaturenis in contact with the cores of the bobbinsm,m1, then the piece of brassrmakes contact with the metal stripsss, and so makes a short circuit for the electric current. An ordinary telephonet,Fig. 61, in which some small shot, bells, &c., are placed, is fixed to the top of the brass cylinderf.
Action of Circuit Closer.—The action of this apparatus is as follows:—
On the mine carrying this form of circuit closer being struck by a passing vessel, the weightais caused to fall over towards the side of the brass cylinderf, thus allowing the strong spiral springhto act on the brass rodgin an upward direction, by which means the armaturenis brought into contact with the soft iron cores of the bobbinsm,m1.
Mc.EVOY'S MAGNETO ELECTRO CIRCUIT CLOSER.Plate XV
Mc.EVOY'S MAGNETO ELECTRO CIRCUIT CLOSER.
The connections of the wires are made as follows:—
The line wirewis led through the base of the apparatus and connected to a piece of brass under the ebonite supportl, in connection with one of the wires of the bobbinm, the other wire of which is attached to the metal strips; the wires of the bobbinm1are connected, the one to the metal strips1, the other to a piece of brass under the ebonite supportl; from this latter piece of brass a wirew1is led to the brass screwx. The wiresw2,w3, from the fuzes are led, the one to the brass screwx, the other to a screwy, which forms through the metal of the apparatus the earth plate. One of the wires of the telephonetis connected to the brass screwx, the otherw4is connected to the piece of brass to which the line wirewis also attached. While the circuit closer remains in a state of rest, the current from the signalling battery flows along the line wirew, up the telephone wirew4, through the telephone which has a high resistance, then by the wirew2through the fuzes, and to earth by the wirew3.
On the circuit closer being struck, by which cause the armaturenis brought up to the cores of the bobbinsm,m1, and the piece of brassrin contact with the metal stripss,s1, the signalling current, instead of circulating through the high resistance of the telephonet, passes round the bobbinm, down the metal strips, across the brass piecer, up the metal strips1, round the bobbinm1(thus forming an electro magnet ofm,m1), and by the wirew, direct through the fuzes to earth, and so explodes the torpedo. The effect of the telephone resistance being cut out, is to strengthen the signalling current, and enable it to work the shutter apparatus and so throw the firing battery in circuit and explode the mine.
The advantages of this circuit closing apparatus are:—
1.—Simplicity.
2.—Compactness.
3.—Increased certainty of action, due to the sustained contact of the armaturen, on the apparatus being struck.
4.—Additional means of testing a system of electrical submarine mines, which is afforded by the telephone:—
When this form of circuit closer is put in action by a friendly vessel coming in contact with it, or when experiments are being made, the signalling current must be reversed, so that no doubt may exist as to the armaturenhaving dropped, on the apparatus coming to rest.
The telephone test indicates whether the circuit closer is in position or not, the shot, &c., within the telephone being shaken about by the movement of the buoyant circuit closer, the noise so created is readily distinguished by the receiving telephone at the station.
Another form of submarine mine is that known as the "Electro Mechanical" mine. The difference between this form and an ordinary mechanical mine is, that the exploding agent is electricity, and that it may be converted into an electro contact mine if desirable.
Description of a Russian Electro.—The electro mechanical mine, used by the Russians during the late Turco-Russian war, is shown in elevation and section atFig. 62and63.
Mechanical Submarine Mine, used by them during the late Turco-Russian War.—Ais the conical shaped case;Bthe loading hole;Cthe base plug;D,D, &c., are five horns, screwed into the head of the caseA; these are composed of a glass tubeA, containing a chlorate of potash mixture, enclosed in a lead tubeB, over which is screwed a brass safety cylinderC; when ready for action this latter tubeCis removed; directly beneath each of the hornsA, on the inside of the case, as atE, is a thin brass cylinder, closed at one end by a piece of woodd, and containing several pieces of zinc and carbon, arranged in the form of a battery, the zinc and carbon wireszandxbeing led through the piece of woodd;Fis a copper cylinder containing the priming charge of gun-cottong, and detonating fusef; the terminals of the fuze are connected to two insulated wires,wandw1, the former of which is led direct to the loading holeB, and attached on the inside to the five zinc connecting wiresz, &c.; the latter is attached to one end of a safety arrangementS, the other end of which is connected to the wirew2, which is attached on the inside to the carbon wiresx, &c.; the safety arrangementSconsists of an ebonite cylinder, containing a brass spiral spring fixed to one end of it, and pressing against a brass plate at the other, thus preserving a metallic connection between the wiresw1, andw2; the mine is rendered inactive by pressing the spring down, and inserting a piece of ebonite between it and the plate.
Its Action.—The action of this form of electro mechanical submarine mine is very simple; the brass safety cylindersc,c, &c., being removed on a vessel striking either of the horns,D,D, &c., the lead tubebis bent, causing the glass tubeato be broken, and the mixture contained therein to flow into the cylinderE, instantly generatinga current of electricity in the zinc carbon battery, and exploding the mine.
Mode of Converting into an Electro Contact or Observation Mine.—To convert this mine into an electro contact one, it is only necessary to connect the wiresw1andw2to other wires leading from the shore; also by replacing the hornsD,Dby solid brass screw plugs, the mine may be converted into an ordinary observation one. In this case the two wireswandw1attached to the fuzef, terminals would have to be connected to the observation instruments on shore.
Turkish Vessel sunk.—It was by means of one of these electro mechanical mines, that the Turkish gunboatSunawas sunk at Soulina.
Firing by observation, that is to say, effecting the ignition of an electrical submarine mine at the precise moment of a hostile vessel being vertically over it, through the agency of one or two observers stationed at a very considerable distance from the mine, should, with the very perfect self-acting circuit closers that exist at the present time, be resorted to only in very exceptional cases, or in connection with the self-acting system.
There are two defects, which are common to all methods of firing submarine mines by observation, and these are:—
1.—At night time, or in foggy weather, it cannot be employed.
2.—It is necessary to employ at least two observers, at a considerable distance apart, who to effect a proper action at the right moment, must work in perfect unison. These defects alone are sufficient to explain the preference given to a self-acting method of closing the electric circuit at the precise moment of a vessel being in position over a mine by those governments who have adopted electrical submarine mines as a means of coast defence.
Methods of Firing by Observation.—There are several methods of firing by observation, of which the following are the ones principally used:—
Intersection by Pickets or Range Stakes.—In narrow channels and at short distances, this system of ascertaining the relative position of a hostile vessel and a submarine mine may be used, provided that skilledand careful men are employed to work it. Two or more pickets or stakes are arranged in front of the firing station in such a manner that a vessel passing up the channel on the prolongation of these stakes will be over a mine. This arrangement should of course always be considered as an extempore one; it was used on several occasions by the Confederates during the American civil war.
Firing by Cross Bearings.—The simplest method of so determining the relative position of a vessel and a submarine mine, and exploding it at the right moment, is that in which observers are placed on the prolongation of the mines. This mode is shown atFig. 64, wherem1,m2,m3, &c., andn1,n2,n3, &c., are the mines;AandB, the points in prolongation of the mines where the observers are stationed;Dthe firing battery, ands, ands1two hostile vessels.
At the stationsAandBfiring keys are placed, at the former one for each separate mine, perfectly distinct and insulated from each other, at the latter a single key. The pivot points of the series of keys atAare connected by separate wires to one pole of the firing batteryD, the other pole of which is connected by a single cored insulated cable to the pivot point of the key atB; the contact points of the series of keys atAare connected by separate line wires asA m1,A m2,A m3, &c., to the different mines, while the contact point of the key atBis put to earth. Thus it will be seen that, in the case of the row of mines,m1,m2, &c., unless the key atB, and the key atA, of either of those mines are both pressed down at the same instant, no current can pass, and therefore none of those mines can be exploded.
RUSSIAN SUBMARINE MINE, FIRING BY OBSERVATION.Plate XVI
RUSSIAN SUBMARINE MINE, FIRING BY OBSERVATION.
In the case of the vesselS, though atC, she is on the prolongation of the lineA m5,C, and therefore the key of the minem5, is pressed down atA, yet not being on the prolongation of the lineB,E, the key atBis not pressed down, therefore the firing battery is not thrown in circuit, or the minem5exploded, but when the vesselsreaches the positionN, that is over the minem3, she being on the prolongation of the linesA m3, andB E, the key (m3) atA, and the key atBwould both be pressed down, and therefore the minem3exploded, and the ship destroyed. In the case of a vessel passing through an interval between any two mines at such a distance as to be out of the radius of destructive effect of either of the mines belonging to the first row (which is shown ats1,) only the key atBwould be pressed down, and thus the vessel enabled to pass safely through, but only to cometo grief at the second or third row of mines, provided they have been properly placed, and separate though similar arrangements as in the case of the line of mines,m1,m2, &c. have been made.
Firing by a Preconcerted Signal.—AtFig. 65is represented a somewhat similar, though a much simpler plan of the foregoing system, by employing a preconcerted signal at the stationBin the place of the firing key and insulated cable, as in the former case. The only material difference in the arrangement of these two methods, is that in the latter case the pole of the firing battery atA, which in the former case was connected to the firing key atB, is put direct to earth. As will be readily understood, this latter system requires great coolness and nerve on the part of the operator atA, who has not only to watch the vessel passing across his intersections, but also to be on the alert to receive the signal from the observer atB. Should it ever be necessary to adopt this latter system, it will be found advisable to employ two men at stationA, one to watch stationB, the other to attend to the firing key and intersections. A separate signal-flag for each line of mines, and also a separate firing arrangement, would be required. As in many cases it would not be practicable to have a station in such an advanced position as atB, inFig. 64and65, on account of the danger of its being cut off by an enemy, another combination becomes necessary. In this instance the stationBis placed on the opposite side of the river, &c., to that on which the stationAis placed, and a series of firing keys, instead of a single one, is here used, necessitating a multiple cable between the stationsAandB, in the place of single cored cable; the manner of manipulating this method is very similar to that previously described.
Firing by Intersectional Arcs fitted with Telescopes.—The foregoing methods of firing by cross bearings are replete with many serious defects, to remedy which, to a considerable extent, special arrangements have been devised, that is, the employment of intersectional arcs fitted with telescopes at the stationsAandB.
Fig. 66and67show the arrangements of these arcs, the former being the one used at the firing stationA, the latter at the converging stationB. At each station one arc is provided for each row of mines placed in position. The firing arcFig. 66consists of a cast iron framea, with three feetb,b,b, these being provided with levelling screws.
To ascertain when this frame is level, a circular spirit level is attachedthereto, a telescopedprovided with one horizontal and three vertical cross wires, supported on Y's, admitting of vertical motion and attached to an uprighte. A mill-headed screwfenables the telescopedto be raised or lowered; the telescope, which is rigidly connected to a vernierg, traversing over a graduated arch, can be moved rapidly in a lateral direction by means of a rack and pinion arrangementi, and it can be clamped in any position by means of the screwh. Sights are fixed on the telescope in a vertical plane passing through its axis. To the outer rim of the frame of the arc, which is smooth, are secured the sightsl l(shown on a large scale at Fig. 68), to give the direction of the mines. These sights are provided each with a brass point of V form,m, and a binding screw,n, in metallic connection with each other, but insulated by means of an ebonite plate from the rest of the metal of the sight. One end of a short piece of insulated wire is attached to the binding screwn, and the other passes through a hole in the base of the sight and projects below it;ois a brass tube rigidly connected to and moving with the upright carrying the telescoped, and projecting in front of this latter. A brass springp(see Fig. 69) is attached to, but insulated from the outer extremity of this tube, and is so arranged as to make contact with the V pointmon the sight, by means of a corresponding projection fitted to its under side. An insulated wire passing the tubeo, the outer end of which is connected to a screw on the springp, forms a metallic connection between this projection and the firing key.
AtFig. 68is shown an enlarged view of the front of the sight; in addition to the V projectionm, and binding screwn, it is fitted with a capstan-headed screw to bear against the inner rim of the frame, and a thin wire uprighttfor giving the alignment of the mine, to which a disc is attached, on which the number of the mine is affixed.
When the distance between the station and the mine is only about one mile, an ordinary eyepiece is used in the place of the telescoped.
AtFig. 67is represented the arc employed at the converging station, which with the exception of there being no tubeo, and only one sight, is precisely similar in construction to the one used at the firing station, and which has been described.
APPARATUS FOR FIRING BY OBSERVATION.Plate XVII
APPARATUS FOR FIRING BY OBSERVATION.
Application of the Intersectional Arc Method.—The application of the method of firing by observation, by means of intersectional arcs fitted with telescopes, is shown atFig. 70.C,D, andEare three of thelarger kind of arcs, one being used for each row of mines at the firing stationA. At the converging stationB, one of the smaller arcs is used for each row of mines, as shown atF,G, andH.S,S1,S2, are the signalling apparatus, theFterminals of which are connected to the sightsl,l,l,Fig. 69, of arcsC,D,E. Firing keysa,a,aat stationAare connected to each arc, and to three of the cores of the cable connecting the two stationsAandB, respectively. At the converging stationB, three firing keysb,b,bare connected to earth and to three cores of the connecting cable respectively. The remaining core of this cable is connected to the recording instrumentsd,e. The action of the arcs, &c., will be readily understood from the diagram atFig. 70.
This arrangement does not interfere with the action of the circuit closer, as all that is effected by the observing arc circuit is to put the signalling battery current at the converging stationBto earth instead of at the circuit closer.
Prussian System of Firing by Observation.—The principle on which this system is based, depends upon the proposition that ifc d, in the triangle shown inFig. 71, be always kept parallel toH B, thenA c,c d,d Abear exactly the same proportion to each other asA B,B H,H Ado to one another; so that by means of the small triangleA d c, the lengths of the sides of the large triangleA B Hcan be obtained, and hence the position of the pointH, the baseA Bbeing of course known. InFig. 71atAthere is a slate table representing the roadstead, and upon it the exact position of every torpedo is laid down, corresponding to their position in the roadstead. AtAandB, 500 yards apart, telescopes having cross wires are placed; atAa long narrow straight-edged strip of glassA dis arranged to move in unison with the telescope atA; and by the application of dynamo electricity, a similarly constructed piece of glassc dmoves in exact unison with the telescope atB, and having its pivot atC; that is to say,C dkeeps parallel withB H, the line of sight of the observer atB.
Then if the observers atAandBhave got a ship in their telescopes, the point of intersectiondof the two pieces of glassA dandC dgives the position of the ship on the slate table atA, and when this pointdcomes over the position of any one mine on the slate, it is known that the ship is over that particular mine in the harbour, and she may be destroyed accordingly, by throwing the firing battery into circuit.
By the employment of electricity and a mirror, the great defect of this method, viz., the necessity of employing four people to manipulate it, would be remedied. The foregoing is a modification of Siemens's method of ascertaining distances at sea, &c.
Rules observed in Planting Mines.—In placing a system of submarine mines in position, the following are some of the chief points to be attended to, this work depending in a great measure on local circumstances, and on the method that is to be adopted in exploding and mooring them:—
1.—The plan of defence must be carefully laid down on a chart, on a scale of not less than six inches to the mile, and on this plan are to be marked the sites of the observing stations, the positions of each mine, circuit closer, and junction box, with their corresponding numbers, and also of the electric cables.
2.—The position of each mine having been determined, should be marked off by buoys.
3.—The utmost care should be taken to lay the electric cables, so that they shall be as far as possible away from the mines in the vicinity of which it may be necessary to take them, so as to lessen the liability of injury to them, by the explosion of the latter.
4.—The electric cables should be laid parallel, and never be allowed to cross directly over each other, otherwise the operation of underrunning them will be much complicated, also a certain amount of slack should be allowed to facilitate in picking the cables up for repair, &c.
5.—Every manner of device is to be used to conceal the electric cables, such as laying dummies, making detours inland, &c.
6.—All marks indicating position of the mines to be removed, after the mines have been placed in position.
7.—The identity of each cable and mine to be very carefully preserved throughout, by means of a number.
8.—A number of electro contact mines should be placed in advance of the leading line of mines, at irregular intervals, to prevent the enemy, having once ascertained the position of one mine of a line, from knowing within limits the position of the others of that line.
SYSTEMS OF DEFENCE BY SUBMARINE MINES.Plate XVIII
SYSTEMS OF DEFENCE BY SUBMARINE MINES.
In connection with a system of defence by electrical submarine mines, the following batteries are required:—
Firing Battery.—The firing battery should be suited to the nature of the fuze employed, and should possess considerable excess of power to enable it to overcome accidental defects, such as increased resistance in the various connections, or defective insulation in the line wire, &c.
As platinum wire or low tension fuzes are now universally adopted as the mode of ignition for submarine mines, it will be only necessary to describe those electrical batteries which are most suitable as an exploding agent in connection with such fuzes; these are as follows:—
Siemens's Low Tension Dynamo Electrical Machine.—This instrument consists of an electro magnet and an ordinary Siemens armature, which, by the turning of a handle, is caused to revolve between the poles of the electro magnet. The coils of the electro magnet are in circuit with the wire of the revolving armature, and during rotation the residual magnetism of the soft iron electro magnet cores at first excites weak currents which pass into the electro magnet coils, increasing the magnetism of the core, thus inducing still stronger currents in the armature wire. This accumulation by mutual action goes on until the limit of magnetic saturation of the iron cores of the electro magnets is reached.
By the automatic action of the machine, the powerful current so produced is sent into the leading wire or cable to the fuze to be exploded.
In this apparatus the electric current passes continuously through the line wire until a sufficiently powerful current is generated to heat or fuze the bridge of the fuze, and so ignite the gun-cotton priming. The coils of the armature and electro magnets are wound with wire of large diameter, to a total resistance of 8 to 10 Siemens units, or 7·6 to 9·5 ohms, in about 2,000 windings.
With a platinum wire weighing 1·65 grains per yard, 6-1/2 inches can be fuzed on short circuit, and 14 inches can be heated to redness.
The total weight of this machine, which is manufactured by Messrs. Siemens Brothers, is about 60 lbs.
Advantages of Siemens's Dynamo Electrical Machine.—The advantages of such a machine over Voltaic apparatus are:—
1.—The absence of chemical agents.
2.—There is less liability to get out of order.
3.—No special knowledge is required to work them, or to keep them in order.
4.—Greater durability.
The great defect of this and all similar machines is that the electric force has to be developed by turning a handle for a certain time before it is possible to generate a current sufficiently powerful to ignite a fuze, which defect, in connection with a system of defence by self-acting submarine mines, particularly at night, renders them inferior to Voltaic batteries, as under such circumstances, an apparatus is required that will cause an electric current to flow at any moment when the circuit is completed.
The application of steam power would to a certain extent remedy the above-mentioned defect, but the cost of such a method, compared to that of a Voltaic arrangement, would be far too great to allow of its superseding the latter arrangement.
Von Ebner's Voltaic Battery.—This form of Voltaic battery, which may be considered as a modification of that known as Smee's, was designed by Baron von Ebner, colonel of the Austrian imperial corps of engineers, for use in connection with the Austrian system of submarine defence, by self-acting electrical mines.
A section of one of these cells is shown atFig. 72. It consists of a glass vessela, to contain the diluted sulphuric acid, within which is suspended a platebof platinised lead, which is bent round into a cylindrical form to fit close around the inner surface of the glass vessel. In the centre of this latter is hung a porcelain perforated cupc, containing some cut-up zinc and mercury to keep it (the zinc) amalgamated. The top of each cell is furnished with a porcelain cover, through which the wires attached to the positive and negative poles of the cell project.
Due to the large quantity of liquid contained in the cell, thetendency to alter its internal resistance is retarded; also by the arrangement of the porcelain cup, above detailed, the consumption of zinc and mercury, which in an ordinary Voltaic battery is very considerable, is materially diminished.
Chromic Acid or Bichromate Battery.—This form of battery is very similar to Grove's, the difference being that, in the place of the nitric acid as the exciting liquid, either chromic acid, or a solution of bichromate of potash, sulphuric acid and water is substituted.
A form of this battery, as designed by Dr. Hertz, is used in connection with the German system of torpedo defence.
Leclanché Voltaic Battery.—This form of Voltaic battery was invented by M. Leclanché, some twelve years ago. AtFig. 73is shown a cell of this battery in its original form. The positive poleaconsists of a plate of graphite in a porous potb, and surrounded by a mixture of peroxide of manganese and graphite. The negative polecis a rod or pencil of amalgamated zinc. The whole is enclosed in an outer vessel of glassdcontaining a solution of sal ammoniac.
A modified form of the Leclanché cell as used in a firing battery is shown atFig. 74. It consists of an ebonite trough or outer vesselaabout 16" long, 9" deep, and 2-3/4" wide. The negative pole or zinc platebis of similar shape to the trougha, but with its base removed, and does not fit the trough exactly, the space between it and the trough being left to ensure the former being completely surrounded by the sal ammoniac solution; the positive pole, or carbon element, consists of four gas carbon platescattached together at their head by means of lead, and enclosed in a flannel bag, in which they are firmly embedded in the peroxide of manganese mixture; the positive element is of such a shape that it fits loosely between the sides, and is nearly of the same height as the zinc plate.
The object of such a form of cell was to obtain an electric current of largequantity, with as few cells as possible, by which means the loss of power which might occur from the employment of a great number of small cells is avoided.
Advantages of a Leclanché Firing Battery.—The advantages of the Leclanché firing battery are:—
1.—The absence of chemical action when the battery circuit is not complete, and consequently there is no waste of material.
2.—Requires little or no looking after.
3.—It may be kept ready for action in store without in any way deteriorating.
4.—It is comparatively very cheap.
These advantages combine to make a Leclanché battery the most suitable of any other form of electrical battery for use as the exploding agent for electrical submarine mines, and it is now universally used for such purposes.
Signalling Battery.—The signalling battery should be so constituted as to be capable of working the electro magnet of the shutter apparatus effectually when the circuit is closed direct to earth, and yet not so powerful as by the continuous passage of the current generated by it to fire the fuze in the mine. In the case of a platinum wire fuze being in the circuit, plenty of power may be given to the battery without fear of a premature explosion from this cause, but in the case of a high tension fuze it is necessary to be very careful in order to guard against such a contingency.
As in the case of a signalling or shutter battery, the electric current will be continually flowing, it is necessary to employ a constant battery, or one that requires least trouble and expense to maintain it in working order, and it is for this reason that a modified form of Daniell battery has been adopted to work the shutter apparatus.
Daniell Signalling Battery.—AtFig. 75is shown the manner of arranging a Daniell cell. A glass or porcelain vesselacontains a saturated solution of sulphate of copper, in which is immersed a copper cylinderbopen at both ends and perforated by holes; at the upper part of this cylinder there is an annular shelfd, also perforated by holes, and below the level of the liquid; this is for the purpose of supporting crystals of sulphate of copper for the replacing of that decomposed as the electrical action proceeds. Inside the cylinderbis a thin porous vesselcof unglazed earthenware; this contains either water, or a solution of common salt, or dilute sulphuric acid, in which is placed the cylinder of amalgamated zince. Two strips of copperpandn, fixed by binding screws to the copper and to the zinc, serve for connecting the elements in series, or otherwise.
For the purposes of testing, either the Leclanché or Daniell battery specially arranged, or the Menotti battery, which is really a modification of the Daniell, may be used.
FIRING BATTERIES, TESTING BATTERIES.Plate XIX
FIRING BATTERIES, TESTING BATTERIES.
Description of a Menotti Cell.—A Menotti cell, shown atFig. 76,consists of a copper cup containing some crystals of sulphate of copper and covered with a fearnought diaphragma, placed at the bottom of an ebonite cellb; over this cup is put some sawdust, and resting on top of this is a disc of zinccon another piece of fearnought. The upper portion of the zinc and its connection with the insulated wire are carefully insulated. Fresh water poured on the sawdust renders the battery active.
Description of a Menotti Test Battery.—Fig. 77represents a plan of the top of such a test battery with a 20-ohm galvanometer attached thereto. The connections are made as follows:—
One of the wireswof the object to be tested is attached to the terminalf, which is also connected by an insulated wire to the copper cupa; the other main wirew1is attached to the terminalgof the galvanometer;h, the other terminal of the galvanometer, is connected by a short piece of wirekto the terminallof the contact keym; and the contact pointnis in connection with the zinc platec; thus the current from the battery flows along the wirewthrough the object to be tested, back along the wirew1, through the coils of the galvanometer, along the wirekto the contact keym, and if this is pressed down to the zinc platec, so completing the circuit.
To steady the needle of the galvanometer a bar magnet is used, which is inserted in the spacer. The whole of the apparatus is enclosed in a leathern case fitted with a cover and strap.
This is a very compact and simple form of test battery, and will be found extremely useful in boats, &c., when placing mines in position.
Telegraph Battery.—For the purposes of telegraphing between torpedo stations, &c., a form of Leclanché battery, known as No. 3 commercial pattern, is generally used.
Voltaic Batteries.—The following points in connection with the use of voltaic batteries, which are taken from Beechey's 'Electro Telegraphy,' should be carefully observed:—