It is very interesting to watch the uses to which the electric light is being put. The latest experiment has been made by an Austrian, Doctor Mikerliez. Almost incredible as it may seem, the interior of the human stomach can now be illuminated by means of a wonderful little instrument called the Gastroscope, which is said to be actually in use and to have been favourably reported upon by the medical faculty of Vienna. There is at the end of a jointed flexible tube (which can be passed down the gullet) a miniature lamp, far more marvellous and mysterious than that of Aladdin, in which a strip of platinum is fixed and connected with fine wires conducting the electricity from a small battery. When contact is made, and the “light turned on,” the cavernous interior of the stomach is lit up. Still more extraordinary is the fact that the tube can be made to revolve, and the light reflected from the walls of the stomach and directed to the eye of the observer. There is necessarily a bend in the instrument, so that the light has literally to turn a corner before it reaches the surgeon’s eye; here the inventor’s skill and thorough knowledge of the laws of optics are brought into requisition. The reflected rays of light fall upon a sort of window situated a little above the lantern, and by means of prisms and a series of lenses, the light is twisted and turned about until it arrives at the eye-piece. No sensation of heat is to be feared, the little lamp being kept constantly cool by a reservoir of water.
Several contrivances have been invented within the last few years for examining the interior of the body, but they are very costly; the Gastroscope is likely to render great service to medical science.
The term “magneto-electric machine” is given to a collection of parts of mechanism intended to create or gather together induced electric currents. The invention of the magneto-electric machine was by no means a sudden inspiration, but the gradual result of a series of experiments and discoveries, the first of which, dating from 1820, may be said to be Œrsted’s observation, that a magnetised needle is deflected by the approach of an electric current as well as by that of a magnet, clearly proving that magnetism and electricity have some relation to one another. In the same year Arago discovered that a coil of insulated wire wound round a core of soft iron, converts it into a powerful magnet (i.e., an electro-magnet) when a current passes through the coil. It was in 1830, however, that our countryman Faraday proved the creation of a current by the action of a magnet on a coil of wire, and his experiment proved shortly as follows:—If a coil of wire be wound on a hollow core, and a permanent bar magnet be introduced into the hollow core, whilst introducing it a current may be proved (by a galvanometer), to be induced in the coil flowing in a certain direction, A B, which ceases as soon as the magnet is at rest in the centre of coil. On the withdrawal of the magnet a second current is induced flowing in the opposite direction, B A. Therefore it is clear that if a magnet be incessantly approached to and withdrawn from a coil of wire a constant succession of currents will be produced, and if a charged coil (i.e., a coil connected with the poles of a voltaic battery) take the place of the magnet a precisely similar result will be obtained. Now it will have been noticed that two opposite currents are constantly being formed, and as the object is to obtain a continuous flow of electricity in one given direction, or, in fact, divert or reverse the current instantly on its formation to make it practically the same current, for this purpose a commutator is used, and as for most purposes a commutator is one of the essentials of a magneto-electric machine, we will here give a description thereof. (See fig. 275.) The machine is composed of a cylinder, consisting of two metallic conducting halves, separated by a non-conducting layer. Whilst it is at rest the alternating currents, from being connected with the halves by the current, will pass to the two contact springs, and thence through the circuit. Now if (as is the case) the current is constantly changing, as has been noticed, the inverse current will at the first change pass through the same channels, but in another direction; but if at the instant of the reversal of the current the cylinder be revolved, the current flowing the reverse way will be guided through other channels respectively, instead of the original channels, and the direction of the current being changed at the same moment as the current itself, the two inversions neutralize themselves, and one constant current is produced. In a magneto-electric machine the commutator revolves identically with the magnet or armature, and the point at which sparks are being constantly produced is where the contact is being continually broken and made by the passage of the friction springs from over the non-conducting layer. The first machine formed on the basis of Faraday’s experiments was Pixii’s. It was composed of two uprights and a cross bar, to which is attached, hanging poles downwards, an electro-magnet; underneath this, the poles upwards, revolves a magnet. The commutator is fixed on the same axle and revolves with the permanent magnet. Saxton, and subsequently Clarke, made the obvious improvement of making the magnet less cumbrous and fixed, and causing the bobbins of the electro-magnet to revolve before or rather beside its poles; the commutator was fixed at the end of the axle on which the revolving bobbins (or armature) are fixed. Niaudat formed a compound Clarke machine, by setting two horse-shoe magnets a short distance apart. The armature revolves between them, and consists of twelve coils set between two plates; the coils are set alternately and connected,—i.e., the poles of the electro-magnets are set beside one another,—N. to S., S. to N., and so on, so that the N. pole receding produces a current; but the N. pole receding makes the S. pole approach, and produces another current, A B; in fact, a continuation of the same, for the approach of a N. pole naturally produces the same current as the recession of a S. pole; then as the S. pole in turn recedes it produces an inverse current, B A, which is in turn kept up by the approach of the next N. pole, and so on. Each coil is attached to a radiating metal bar, which conveys the current to be redirected to the commutator, which is affixed to the axle of the revolving armature as in Clarke’s machine. In 1854 Siemens completed his machine, the chief peculiarity of which was its cylindrical bobbin; the core is grooved deeply, parallel with its axis, and the wire is wound on cylindrically and covered with plates of brass; one end of the coil is fixed to the metal axis, the other to an insulated ferule at the end of the axis, where is also situate the commutator. This armature revolves between the poles by which it is closely embraced. One of the most celebrated of the magneto-electrical machines is that known as the “Alliance,” invented by Nollet, and perfected by Van Malderen. It is composed of four or six bronze discs, revolving on an axle, round the external circumference of each of which are set sixteen bobbins. This rotating compound armature revolves between four to six sets of horse-shoe magnets, which, being fixed radially to the centre, present in each set sixteen poles to the sixteen bobbins. It will be readily understood that this immense quantity of poles and bobbins produces a highly concentrated current, the ends of which proceed from the axle and an insulated ferule at its extremity.
Fig. 275.—The Wallace Machine.
In 1869 Mr. Holmes perfected his machine, which differs from all previous ones (except Pixii’s), in that the electro-magnets revolve in front of the coils instead of vice versâ; and besides magnetising his electro-magnets with part of the self-produced electricity, his bobbins are so disposed as to be able to keep several independent lights going at once. The Wylde machine consists, as it were, of two Siemens machines, one on the top of the other, the lower and larger of which is worked by an electro-magnet, which is magnetised by the action of the upper or smaller one, consisting in the ordinary way of a permanent magnet apparatus, which is termed “the exciting machine.” The longitudinal bobbin revolved between these permanent poles produces alternating currents, which are commutated (or redirected), and pass to work the larger and lower electro-magnet, which is composed of two large sheets of iron connected by a plate (on which stands the exciter). Its poles are two masses of iron separated by a layer of copper, and in this armature revolves the larger longitudinal bobbin. This lower machine is called the generator. Both bobbins are simultaneously revolved, and an intense current of electricity is thereby generated. Almost simultaneously with this one Mr. Ladd invented his machine, which is distinguished from all hitherto described by being composed of two parallel bar electro-magnets, between the extremities of which are placed two Siemens armatures, one smaller than the other; both being revolved, the smaller excites the electro-magnets, and the larger generates the electricity required. The wire is wound round the magnets so that the N. and S. poles face each other at each end. The chief advantage of the Ladd machine is the conversion of dynamic force into electricity, there always being just sufficient magnetism in an iron bar (by induction from terrestrial magnetism and other causes) to produce a very feeble current in the Siemens bobbin, and the bobbin taking it up and returning it to the electro-magnet, and the electro-magnet at once giving it back to the bobbin, the current gradually increases till the maximum is reached. And when we take into consideration this modicum of utilisable terrestrial magnetism, we may truly say in the words of M. Hippolyte Fontaine, “The mind is lost in contemplation of the succession of discoveries completing one another, and showing that with apparatus of small dimensions an infinite source of electricity could be produced if matter could withstand infinite velocities.” The Lontin machine, which supplied the current for the electric light which used to make night bright outside the Gaiety, is also composed of two parts, one dividing, the other generating the electricity produced. The principle of the dividing machine is somewhat similar to the alliance, excepting that a number of electro-magnets arranged radially round a core, revolve close to a corresponding number of bobbins fixed inside an iron cylinder, outside which is the collecting and dividing apparatus. The Maxim machine is constructed on the principle of sets of coils rotating between powerful electro-magnets. The Wallace machine was invented by the inventor of the Wallace-Farmer lamp. It consists of two horse-shoe electro-magnets placed side by side, the opposing poles facing each other. Each magnet has a rotating armature of twenty-five bobbins, on which the wire is wound quadruply, and the current generated by these coils is conducted away, passing through and exciting the electro-magnets, thus utilizing the residual and terrestrial magnetism before mentioned in connection with the Ladd machine; otherwise it partakes of the nature of the Niaudet machine.
Fig. 276.—The Gramme Machine.
We now come to what is perhaps the most perfect magneto-electric machine, which was first constructed by M. Gramme, a Parisian, in 1872, and differs in principle and construction from all those hitherto noticed. Its essential characteristic is a soft iron ring, round which is coiled one single continuous wire (i.e., the two ends are joined). Round the exterior surface of the wire coil a band is bared, and on this bared part two friction springs act. If the ring and coil be placed before the poles of a magnet, the ring will have two poles, S. and N., induced opposite the opposing poles N. and S. of the magnet; and if the ring revolve the poles will remain stationary, and as the coil revolves each coil of the wire will pass this induced pole, and as naturally half the coil will be inducted with one current, the other half (acted on by the other pole) will be charged with another or opposite current, which two kinds of electricity are carried away by the friction springs before mentioned. In the machine, as actually constructed, the soft iron ring is composed like the magnet or wire bundle of an induction coil, and the coils are set upon it side by side. Inside the ring are radially set insulated pieces, to each of which is attached the issuing end of one and the entering end of another bobbin; these answer the same purpose as the denudation of the external layer of wire. These pieces are bent so as to come out of the centre of the ring at right angles, and lay side by side (insulated) round a small cylinder. These, as they revolve, are touched by friction springs, which draw off the electricity induced in the coils in one continuous current. No sparks are produced at the contact of the friction springs, and there is no tendency to become heated. To obviate the inconvenience of the secondary or inverted current produced by the stopping of the machine, the inventor has contrived a circuit breaker on the principle of the electro-magnet, the magnets holding the circuit breaker in contact so long as the machine is working; but the decrease of velocity lessening the attractive power of the magnet, the circuit breaker opens by its own weight (or a counter-weight), and all danger of a reverse current is obviated. Experimental machines are manufactured by Bréquet & Cie (Paris), composed of Jamin’s magnets, and turned with a handle, and produce a force of eight Bunsen cells.
A great revolution, or rather the beginning of a new era in the history of electricity, may be said to have commenced with the perfection of M. Faure’s accumulators. These are troughs containing eleven lead plates, each coated with oxide of lead and wrapped in felt, the fluid being dilute sulphuric acid. The application of them to the electric light is one of their most valuable features; at the depôt in the Strand, where they may be seen at work, there are thirty such elements, each weighing about 50 lbs. It takes a two-horse-power engine working an Edison or Gramme machine six to eight hours to charge them, and when charged they will keep almost any number of lamps of sixteen-candle-power going some eight hours. They are used on the Brighton and South Coast Railway, and seem peculiarly adapted to lighting by incandescence, by Swan, or Edison’s lamp. The elements fully charged may be carried any distance without losing their electric power. And the stored force may be used for charging the accumulators themselves afresh from the machine. These accumulators may be seen any day at 446, Strand, and are well worth a visit.