,transcriber's ,notes3 ,underscores 80 before and after a word or phrase indicate italics in the original text4 ,carat symbol 80 designates a superscript4 ,small capitals have been converted to ,,solid capitals4 ,illustrations have been moved so they do not break up paragraphs4 ,typographical errors have been silently corrected but other variations in spelling and punctuation remain unaltered4 ,,history ,,of ,,the ,,transformer4 ,,by ,f4 ,,uppenborn1 ,,editor ,,of ,,the 8,,centralblatt ,f,r ,,elektrotechnik10 ,,and ,,chief ,,of ,,the ,,electro-,,technical ,,testing ,,station ,,in ,,munich4 ,,translated ,,from ,,the ,,german4 ,illustration ,e4 ,f4 ,n4 ,,spon1 #abe1 ,,strand1 ,,london4 ,,new ,,york3 #ab1 ,,cortlandt ,,street4 #ahhi4 ,,preface4 ,as of late the employment of alternating current transformers has largely increased and become of great importance1 indeed as they are called upon to play a striking part in electric lighting from central stations1 the author has thought a short notice of the development of this invention would possess some interest4 ,this task appeared to be so much the more pressing1 as many distorted versions of the invention and its priority have found place in the technical journals4 ,the author has not let the reading of the large number of patents discourage him1 and hopes that the following plain and concise statement of these researches will contribute towards the forming of a correct judgment as to the services rendered by the several inventors4 ,,the ,,author4 ,,history ,,of ,,the ,,transformer4 ,as we wish to write of those discoveries which led up to the invention of the transformer1 we must go back to a time1 old as compared with the modern development of electrotechnics4 ,for the starting-point of our observations we shall take ,faraday1 who1 like ,newton in mechanics1 led the way in the domain of electricity1 and whose name stands in the most intimate relations with all inventions for the mechanical production of the electric current1 and therefore with the later development of electrotechnics4 ,sidenote3 ,faraday1 #ahca4 ,the most important discovery for which we have to thank ,faraday is that of induction4 ,this discovery was made by him in the year #ahca1 and intimated to the philosophical world in a paper read on the #bdth ,november1 #ahca1 appearing in the ,transactions of the ,philosophical ,society in the year #ahcb4 ,faraday's first induction apparatus consisted of two coils of wire1 the one being slid over the other4 ,as he was passing the current from a battery through one of these1 he made the discovery that each time the circuit of the coil was opened or closed an electromotive force was created in the second coil1 which caused a short gush of current or induction current to flow1 provided the circuit of this coil was closed1 as might be through a galvanometer4 ,the peculiarity of this induced current was1 that it only flowed in the second coil during the time the current in the first coil took to reach its normal strength after closing the circuit1 or on breaking the circuit during the time the current took to decrease from its normal strength to zero4 ,this discovery undoubtedly belongs to the domain of the transformer1 induction being the physical precedent upon which the transformer is based2 indeed1 a transformer is in principle an induction apparatus4 ,illustration3 ,,fig4 #a4 ,fig4 #a represents the arrangement of this fundamental experiment4 ,the primary coil is connected with the battery1 the secondary with the galvanometer4 ,the primary coil1 in order to obtain the best effect1 is placed inside the secondary1 and on opening and closing its circuit the needle of the galvanometer is thrown to the one or the other side respectively4 ,illustration3 ,,fig4 #b4 ,the arrangement1 as in ,fig4 #b1 made by ,faraday showed itself to be an especially effective combination for the production of these induction phenomena4 ,there were wound round an iron ring two separate wires of about the same length4 ,the one coil was brought into connection with a battery1 and to the ends of the other a pair of electrodes were attached4 ,the current from the battery being sent through the primary coil1 lines of force were produced which ran almost altogether in the iron core4 ,as the core possessed only a very small magnetic resistance1 the intensity of magnetisation was very great1 and on closing the primary circuit a strong inductive effect on the secondary coil was produced4 ,faraday obtained with this apparatus the first sparks of induction4 ,the apparatus is all the more interesting as1 although not completely without poles1 it at least forms a closed magnetic circuit4 ,it has much likeness to the non-polar transformer of ,zipernowsky1 ,dri1 and ,blthy1 but it may be easily shown to be not entirely poleless4 ,poles mean1 in electrical as well as magnetic circuits1 those points between which the greatest difference of potential exists4 ,a current without difference of potential can only flow in an electrical or magnetic circuit when the loss of potential in each part of the length of the circuit1 viz41 the product of resistance and current1 is equal to the gain of potential1 that is the magneto-or electromotive force2 therefore a current without difference of potential requires that the resistance and magneto-or electromotive force in each part of the length be the same4 ,now the magnetic resistance of a symmetrical iron ring is constant in all parts of the length of its magnetic circuit4 ,in the case in question only one half of the ring was excited1 therefore poles must have been formed at both ends of the exciting coil4 ,the ratio of transformation of this apparatus of ,faraday's was equal to unity1 so it had therefore no claim to the designation of 8transformer40 ,the induction apparatus of ,faraday in its simplicity was in a certain measure the embryo out of which all dynamos and transformers have developed4 ,we have seen how the first induction current was discovered by making and breaking the current from a battery in the primary coil4 ,this method was at first adhered to1 until ,faraday remarked that when the secondary was quickly drawn out of or put into the primary coil1 induced currents were also produced without requiring to break the circuit1 the wires of the secondary coil cutting the lines of force in the magnetic field of the primary coil4 ,he then replaced the primary coil and battery by a permanent magnet1 which was likewise dipped into the induction coil1 ,fig4 #c4 ,illustration3 ,,fig4 #c4 ,sidenote3 ,henry and ,page1 #ahcf4 ,from this1 and from the later development of this invention1 it follows that the question was not of a transformer in the present sense of the word1 but of a secondary generator4 ,transformers as at present understood were first known in ,europe as the ,ruhmkorff's induction coil4 ,before we take up this invention we shall mention a much earlier and like invention1 which had already been made in the ,united ,states in the year #ahch4 ,this was the induction coil of ,professor ,page1 and was the outcome of another invention by ,professor ,henry1 whose apparatus was only a single induction coil4 ,the first public notice of ,professor ,page's apparatus appeared in the ,silliman-,journal of #abth ,may1 #ahcf1 under the title1 8,methods and trials of obtaining physiological phenomena and sparks from a heat engine by means of ,professor ,henry's apparatus40 ,in ,may1 #ahcg1 ,sturgeon published1 in the 8,annals of ,electricity10 in ,london1 a description of the apparatus of ,henry and ,page4 ,sidenote3 ,callan1 #ahcg4 ,callan1 an ,english student of physics in ,minnoth1 showed first1 in the year #ahcg1 that if high tension was wanted1 it was necessary to employ thick wire for the primary and thin for the secondary coil4 ,before this time wires indeed of different lengths1 but of equal cross sections1 had always been employed4 ,his apparatus was not so bad as those before known1 but still stood far behind that of ,professor ,page4 ,sidenote3 ,page1 #ahch4 ,the arrangement of ,professor ,page's apparatus1 which is shown in ,fig4 #d1 was as follows3--,two coils of wire well insulated from one another were wound on to a bundle of iron wires4 ,a self-acting contact-breaker was put into the primary circuit1 and consisted of a double lever ,e1 having on one of its arms two parts bent downwards1 so as to dip into two mercury cups4 ,the movement of the part ,h1 as compared with that of ,e1 was so small that it remained always in the mercury4 ,at ,m1 however1 when the lever was set in motion contact was broken and made4 ,to prevent oxidation ,page poured in a layer of alcohol over the quicksilver4 ,illustration3 ,,fig4 #d4 ,the continuation of the lever in the other direction of the axis1 which was borne by two pillars ,k1 was bent backwards1 and on its end carried a cylindrical piece of iron standing before the end of the bundle of iron wires4 ,if the primary coil were now placed in connection with a source of current1 the iron core became magnetised1 attracted the cylindrical piece of iron to itself1 and by raising the lever ,e broke the contact at ,m4 ,the iron core then lost its magnetism1 released the iron armature1 and the play began anew4 ,a counter-weight ,f1 which could be shifted along another lever ,o1 allowed the play of the contact-breaker to be regulated4 ,it will be found that this interruptor was very like that constructed many years afterwards by ,lon ,foucault4 ,the effects which ,page produced by means of this instrument were much more intense than those produced by ,ruhmkorff with his1 as ,page succeeded with only a single ,grove element in inducing in the secondary circuit such a high electromotive force as produced sparks #d inches in length through a vacuum tube--a result that ,ruhmkorff1 although his invention created such a great and well-deserved attention1 did not attain4 ,in the year #ahej ,page built a much larger apparatus4 ,in order to give some idea of the magnitude of the electro-magnetic forces which came into play here1 suffice it to say1 that the exciting coils could hold suspended in the air in their interior an iron core weighing #ebj kg4 ,the primary or magnetising coil was of square copper wire1 with a side measuring inch1 and a battery of #ej to #ajj ,grove elements was employed1 the immersed area of the surface of the plates being #ajj square inches4 ,this apparatus gave sparks of great length4 ,when1 with maximum currrent strength1 the primary circuit was broken1 sparks of #h inch length were received4 ,sidenote3 ,ruhmkorff1 #ahdh4 ,ruhmkorff constructed1 in the year #ahdh1 the so-called spark-inducer named after him1 the object of which was also to convert currents of low tension into hose of very high tension4 ,with this coil and like coils of larger dimensions effects were produced1 but only such as were afforded by the common forms of frictional electrical machines4 ,all things considered1 it is not a little surprising that while the invention of the ,rhumkorff coil was still in its infancy1 the wonderful output of ,page's apparatus was still1 even in the year #ahea1 quite unknown in ,europe4 ,illustration3 ,,fig4 #e4 ,fig4 #e represents the earlier form of the ,ruhmkorff apparatus4 ,it consisted of a bobbin of good insulating material2 thoroughly dried wood1 or better1 hard rubber4 ,the two end pieces of the bobbin were usually made of grooved glass discs1 and were bound down to the bedplate of the apparatus by two wires4 ,inside the coil was the already often-mentioned bundle of iron wires4 ,the primary or inducing wire was next wound upon the bobbin4 ,as this wire had to carry currents of comparatively great strength1 it consisted of only one or a few layers of thick wire4 ,the circuit of this coil was completed as far as two terminals on the bedplate1 first passing through an interruptor like what has already been described4 ,over the primary coil1 and after a sufficient layer of insulation had been added1 the secondary wire was wound4 ,as this wire was destined for very small currents1 it was of as fine wire as it was possible to wind4 ,in order to obtain high potential it was necessary that the secondary should possess many turns4 ,in the earlier coils a length of between #h and #aj kilometres was used2 in the coils now made this length has been increased to between #ej and #gj kilometres4 ,the ends of the secondary coil were connected to terminals insulated on glass pillars4 ,it was not nearly sufficient insulation for the secondary wire to be covered with silk1 but every layer was well soaked with dissolved shellac1 and then well dried as it should be4 ,a condenser in connection with the primary coil was placed under or in the bedplate1 which was usually a box4 ,this condenser was1 and is still1 often made thus3--,on both sides of a strip of paraffined paper1 several metres long and of convenient breadth1 tinfoil is stuck1 at the same time leaving a sufficient margin of paper for insulation4 ,the whole is then folded together suitably4 ,the effect of the coil is substantially enhanced when the sheets of tinfoil are each connected to the circuit of the primary coil in such a way that the condenser is in shunt to the interruptor4 ,in ,fig4 #f is shown a newer form of ,ruhmkorff's coil1 with an interruptor like the mercury contact-breaker which we have before described4 ,according as the movable weight is raised or lowered1 the oscillations of the lever1 and consequently the induced currents1 follow one another more slowly or more rapidly4 ,sidenote3 ,c4 ,t4 and ,e4 ,b4 ,bright1 #ahee4 ,we find a further development or modification of the invention of ,page and ,ruhmkorff1 patented by the brothers ,c4 ,t4 and ,e4 ,b4 ,bright on #bast ,october1 #aheb1 and ,no4 #bajc in the year #ahee4 ,in the latter of these patents the inventors state what follows concerning the nature of their inventions4 ,illustration3 ,,fig4 #f4 ,illustration3 ,,fig4 #g4 ,illustration3 ,,fig4 #h4 8,a section of an induction coil made after this manner is shown in fig4 #g1 having a very strong effect4 ,the primary wire1 of which only a part is shown1 is wound on an iron core1 and outside is surrounded by an iron cylinder4 ,both of these are metallically connected by the flanges of the bobbin1 which also are of iron4 ,the secondary coil may also be surrounded by an iron tube1 and if the resistance of the circuit be extraordinarily great with still more primary coils1 or it may be also contained in the same tube as the primary4 ,in cases where it is found necessary to increase the quantity of the electro-magnetic effects1 we find that the forms shown in ,figs4 #h and #i are very effectual1 and may by varied on the same principle4 ,the iron core in the middle is wound with the primary wire1 and is surrounded by the other iron cores1 which are fixed into the large flanges of the middle core1 and carry the secondary coils4 ,should still greater effects be required1 more primary or secondary coils connected in series with the others may be added outside1 in order to produce a greater extension of the poles and a more extensive induction40 ,illustration3 ,,fig4 #i4 ,this patent is interesting also for the fact that in it we find a disposition of parts1 viz4 the arrangement of several induction coils in ranks1 and connected with one another in parallel1 which nearly #cj years later was taken up and practically used by ,gaulard4 ,sidenote3 ,harrison1 #aheg4 ,among the patents of the year #aheg there is an ,english one by ,harrison1 claiming as its object the passing of a primary current through one or more induction coils1 and the connection of the secondary coils with the carbons of an arc lamp4 ,there is nothing remarkable in the description4 ,sidenote3 ,jablochkoff1 #ahgh4 ,the last attempt to use induction coils for industrial purposes is met with in the year #ahgh4 ,in this year ,jablochkoff took out a ,german patent1 which was also carried out in practice4 ,he required currents of very high tension to feed his kaolin lamp2 at that time such currents could only be produced by induction coils4 ,he writes as follows in his patent3-- 8,die ,herstellung einer elektrischen ,beleuchtung nach meinen ,system begreift eine ,serie von ,induktionsrollen in sich1 wovon die inneren ,drhte in eine elektrische ,leitung eingeschaltet sind40 ,illustration3 ,,fig4 #aj4 ,jablochkoff used intermittent direct currents as well as alternating currents4 ,the arrangement shown in ,fig4 #aj was for the former4 ,he states concerning this3-- 8,in diesem ,falle sind die ,induktionsrollen mit ,unterbrecher und ,kondensator ausgestattet1 oder man kann auch1 wie die ,zeichnung nachweist1 einen und denselben ,unterbrecher fr alle ,rollen anwenden4 ,die ,induktionsrollen ,b#a ,b#b ,b#c1 nach einen beliebigen ,prinzipe konstruirt1 sind in der ,nhe der ,lichtherde angebracht40 ,concerning the employment of alternating currents1 ,jablochkoff says3-- 8,diese ,disposition weicht von der ersteren nur durch die ,weglassung des ,unterbrechers und des ,kondensators der ,rolle ab40 ,illustration3 ,,fig4 #aa4 ,illustration3 ,,fig4 #ab4 8,die in ,fig4 #aa angewendeten ,rollen sind in ,fig4 #ab detailliert gezeichnet4 ,auf einer kreisfrmigen ,scheibe ,c aus weichem ,eisen erhebt sich in der ,mitte derselben ein hohler ,cylinder b aus ,holz oder anderem isolirten ,materiale2 um den unteren ,teil des letzteren ist die ,hauptspirale a gewickelt1 welche aus bandfrmigen ,kupferstreifen oder anderem ,metalle besteht1 a ist die in gleicher ,weise zusammengesetzte ,induktionsspirale1 deren ,drahtenden zu den ,lichtherden fhren4 ,zwischen den einzelnen ,windungen der ,spirale sind ,streifen aus ,papierkarton oder einem anderen isolirenden ,material angebracht4 ,die ,spirale a ist in die ,hauptleitung1 wie ,fig4 #aa zeigt1 eingeschaltet40 ,the second claim of this patent is also interesting1 and reads as follows3-- 8,die ,einfhrung einer ,serie von ,induktionsrollen in den ,umkreis eines beliebigen ,elektricittsgenerators zur ,erzeugung einer ,serie von ,induktionsstrmen1 welche es gestatten1 ,lichtherde von verschiedener ,intensitt durch eine einzige ,elektricittsquelle zu versorgen1 was zur vollstndigen ,teilbarkeit des elektrischen ,lichtes fhrt40 ,jablochkoff's system as just described was to be seen working in the ,paris ,exhibition of the year #ahgh4 ,a proper industrial application of this system does not appear to have taken place4 ,sidenote3 ,c4 ,t4 ,e4 ,b4 ,bright1 #ahgh4 ,in the year #ahgh the brothers ,bright had also made further progress in the use of induction coils for electric lighting purposes1 and in the same year they took out the ,english patent ,no4 #dbab1 in which they described the use of alternating currents for working secondary apparatus or induction coils placed at various points where light was required4 ,we shall here quote some very interesting sentences from this patent1 which again show that the brothers ,bright knew already in the year #ahgh the properties of transformers suiting them for electric lighting purposes2 indeed they then anticipated the principles contained in the later patent of ,gaulard4 ,here is an abstract from the description3-- 8,at each point where electric light is used1 the electric lamps or groups of such lamps are fed by the secondary coil or coils of an induction apparatus placed there4 ,the primary coils of all the induction apparatus are in the common circuit of one main lead1 which is in connection with a battery or a magneto-electric machine placed in some suitable situation4 ,the size and length of the primary and secondary coils of each induction apparatus is determined according to the number of lamps at each point1 where the secondary current shall supply the electric lighting40 ,sidenote3 ,e4 ,edwards ,a4 ,normandy1 #ahgh4 ,the employment of induction coils for the distribution of light1 heat1 and power was patented in ,england in the same year by ,edmund ,edwards and ,alphonse ,normandy4 ,among other matter in this patent there is as follows3-- 8,at or near every point where it is required that a light shall be produced1 we arrange a coil 7or series of coils7 of insulated metallic wire or ribbon 7preferably surrounding a bar or wires of soft iron71 through which coil or coils the current from the principal wire first described can be passed when desired1 or cut off by means of a key or lever4 ,round1 or adjacent to1 each coil of insulated wire described1 we form one or more secondary coils of insulated metallic wire1 or ribbon1 arranged so that the passage of the rapidly intermittent current of electricity1 as described1 through the primary coil or coils1 generates a corresponding current of electricity in each of the secondary coils40 ,illustration3 ,,fig4 #ac4 ,sidenote3 ,strumbo1 #ahgh4 ,in the same year1 ,strumbo had also constructed a secondary generator like that of ,gaulard1 and a description of it was contained in the newspaper #8,le ,monde1' of #bdth ,october1 #ahgh4 ,it is of note in this apparatus1 which we have illustrated in ,fig4 #ac1 that the primary and secondary wires were wound side by side1 and that both coils had the same relative position to the iron core4 ,sidenote3 ,harrison1 #ahgh4 ,harrison also1 in the same year1 took out a patent having the same object as his of the year #aheg4 ,both patents proposed the connection of induction coils in series4 ,this is especially clearly mentioned in the latter of these1 as there he says that both induction coils are put in circuit at intervals along the main lead1 or primary circuit1 so that one or more coils are near the places where lamps are to be fed4 ,sidenote3 ,meritens1 #ahgh4 ,we find in ,meritens' ,english patent1 ,no4 #ebeg1 of the year #ahgh1 the series connection of primary coils in the dynamo-circuit also described4 ,meritens intended to employ1 in place of the many separately insulated circuits of the alternating dynamos of that time1 only a single circuit1 fed from one large or several smaller dynamos4 ,a large number of induction coils connected in series1 were to have been distributed in the different districts of a city4 ,besides this1 ,meritens made a combination of the secondary coils1 so that he was in a position to produce currents and potentials of various dimensions4 ,sidenote3 ,fuller1 #ahgh4 ,we now come to an inventor1 who1 in his time1 exercised a great influence upon electric lighting by means of transformers1 and whose system was in every way a great advance on those of his foregoers4 ,this man was named ,jim ,billings ,fuller4 ,he began to study electric lighting in his laboratory at ,brooklyn in the year #ahgd1 giving his whole energy for this object4 ,fuller's system of current distribution was first patented in ,america in the year #ahgh4 ,the patent ,no4 is #baj1cag1 of #bfth ,november1 #ahgh4 ,his apparatus is represented in ,fig4 #ad4 ,it consisted of an induction coil on which an electric lamp was mounted1 to all appearances a ,jablochkoff candle4 ,the induction coil1 to which we shall return later on1 was built in the form of two horseshoe magnets joined together1 and having consequent poles at the small coils in the middle1 after the manner of the magnets of a ,gramme machine4 ,the four large coils are the primary or exciting1 the four small coils on the poles of the double magnets are the secondary coils4 ,illustration3 ,,fig4 #ad4 ,the lever ,,mn was of iron1 and served to weaken the effects of induction1 inasmuch as it formed a magnetic short circuit4 ,here we find for the first time the employment of a regulating device4 ,fig4 #ae illustrates the method of connection4#a ,as already mentioned1 ,fuller succeeded in setting aside many of the defects which were adhered to in the many very badly constructed transformers of his predecessors4 ,while he was busy carrying his invention into practice1 he became a sacrifice to his over-great activity1 and on the #aeth ,february1 #ahgi1 he was taken away by illness4 ,only a few hours before his death1 he called his foreman to himself1 and explained to him the principles of his system4 ,after ending his explanations1 he asked him if he had understood all that he had said1 and1 on receiving an answer from him that he had1 he smiled contentedly1 and a few moments later he ended a useful life1 which had given so much promise of good results4 ,sidenote3 ,e4 ,h4 ,gordon1 #ahhj4 ,in the year #ahhj ,edward ,henry ,gordon took out the ,english patent ,no4 #da1hbf4 ,gordon had constructed an electric lamp based on the fact that when a current of sufficient electromotive force was passed over the space between two balls of platinum or platinum iridium1 the balls were rendered glowing white4 ,these balls were suspended by thin platinum wire1 or the supports were of platinum1 serving also to carry the current4 ,for the production of overspringing sparks1 it is well known that a great difference of potential is necessary1 so ,gordon was obliged to have recourse to induction coils1 which he intended to excite by means of magneto-electric machines1 or alternating current dynamos4 ,in his patent he describes how this idea should be carried out1 and he actually did feed two lamps of #ej c4p41 or one of #ajj c4p4 ,the apparatus is described as follows3--8,the primary consists of a bundle of iron wire #ac inch diameter1 and #ah inches long4 ,three layers of insulated wire #jjh inch in diameter are wound on it4 ,the secondary is wound on an insulating tube1 and consists of about two-thirds of a mile of wire #jjjge inch diameter1 covered four times with silk4 ,it is wound in #fj discs40 8,there are three binding screws1 one at each end and one in the centre1 so that the whole coil1 or either half separately1 can be used for one lamp40 ,illustration3 ,,fig4 #ae4 ,we do not find in ,gordon's patent the slightest indication which would justify us in ascribing to him the invention of a system of distribution by transformers as known at the present day1 but1 on the contrary1 it is clearly shown that the fundamental conditions of such a system of distribution were unknown to him1 for he laid the chief weight upon connecting the induction coils in series1 and on the production of high electromotive force necessary for his lamp4 ,over and above this1 he was of opinion1 as he stated prominently1 that the more advantageous kind of dynamo was one such as that of de ,meritens1 having many coils of thin wire1 which were connected to separately insulated leads4 ,let us look back upon the inventions which were made in the domain of electric lighting by transformers from the time of ,faraday's discovery of induction up to the year #ahhj4 ,there we see that three distinct characteristics were possessed by all the systems invented up to that year4 ,these three characteristics lay in the construction1 the ratio of transformation1 and the method of employing the transformers4 ,single transformers1 with two or more poles1 were used4 ,the ratio was either #a3a1 in which case the induction coil is really not a transformer1 or it was from a low to a high electromotive force2 but nowhere do we find that currents of high electromotive force were converted into those of low electromotive force4 ,the idea in the use of transformers was that of division1 not that of distribution of electric energy4 ,the difference between division and distribution of electrical energy is1 in the main1 as follows4 ,by a division of electrical energy it is meant that a fixed amount of produced energy is divided into pre-determined parts of a certain number and size1 while it remains indifferent1 as far as the total energy is concerned1 in what manner and how many of these parts are usefully employed4 ,by distribution of electrical energy it is meant1 on the other hand1 that the energy produced is variable according to the variable requirements of consumption1 the maximum requirement being pre-determined from the number and size of the local requirements1 which also vary relatively to one another4 ,of the last of these systems there is no indication in any of the inventions of induction coils up to this date4 ,if we seek for the cause of these characteristics1 we find that the reason why transformers with two or more poles were constructed is1 that the electricians of those days either did not know or did not understand the principles on which a proper transformer should be constructed4 ,with them the idea of a magnetic pole acting on a wire near it was always present1 while they entirely overlooked the fact that the electro-magnetic force1 not the pole1 produced the electromotive force in the wire4 ,on account of this they were of opinion that free poles in a transformer were not only not a drawback1 but1 on the other hand1 a distinct advantage4 ,we find that ,fuller especially held this view4 ,he sought not only to have in his apparatus two simple poles1 but double poles1 and indeed he patented this arrangement of his transformer4 ,the first claim of his patent reads thus3-- 8,the double electro-magnet herein described1 the main coils of which are included in the circuit of a main conductor from a generator of alternating electric currents1 producing in said magnet consequent magnetic poles1 as shown1 and around which poles are coiled helices of wire for receiving the currents induced by the polar changes1 said helices being included in the local circuit with the lamp40 ,we must bear in mind that1 as far as the ratio and idea of employment of a transformer are concerned1 the problem at that time was quite another to what it is now4 ,at present the transformer serves principally to render possible the carrying of the current to a great distance economically4 ,the electricians of those days were not so far advanced as to be able to run arc lamps independently of one another on the same circuit1 and this they held to be quite impossible1 whether the lamps were connected in parallel or series4 ,that apparatus was thought to be good which allowed separately insulated currents to be led from one source of current1 each separate circuit going to feed a single lamp4 ,the chief reason for this view lay in the fact that the extinguishing of all the lamps in one circuit could easily take place through the fault of one of them4 ,at that time1 when an arc lamp was cut out of circuit1 it was replaced by a fixed resistance1 instead of which it was thought that induction coils would have suited well4 ,it may be casually mentioned that owing to this fact too sanguine hopes of the solution of the problem of independent working of lamps were aroused1 through a want of sufficient knowledge of the laws of induction4 ,there have also been apparatus other than induction coils used for the purpose of making the points of consumption independent of one another4 ,we can only now recall the patent of ,jablochkoff1 ,no4 #afch1 which is based on the principle of connecting condensers into branches of a quickly alternating main current1 from which arc lamps1 c41 were fed2 also a like arrangement by ,avernarius 7,figs4 #af and #ag71 with the use of secondary batteries1 which were to be employed for either parallel or series connection4#b ,illustration3 ,,fig4 #af4 ,illustration3 ,,fig4 #ag4 ,there were no transformers in those days which1 in the present sense of the word 8transformer10 convert high electromotive force to low to suit the consumers4 ,on the contrary the apparatus1 which was then used in electric lighting plant1 was such as converted low into high electromotive force1 or such that the ratio was #a3a1 or nearly so1 according as it was determined by the connection in series of the primary coils1 and the difference of potential at the consumption devices2 for example1 the induction coils of ,b4 ,ruhmkorff1 ,jablochkoff1 and ,gordon4 ,when1 however1 the term high electromotive force is met with in descriptions of the apparatus of that time1 it must be taken to mean a great difference of potential between the terminals of the dynamo1 not between the primary terminals of the transformers4 ,take1 for instance1 #ajj transformers connected in series1 run with a difference of potential at the dynamo of #ajjj volts1 although it was not known at that time how to produce so high an electromotive force1 still this would give across the primary terminals of each transformer the modest difference of potential of #aj volts4 ,in this way the difference of potential at the generator was determined by the number of transformers in series4 ,this system had plainly the great disadvantage1 that no matter how tortuous a path the lead must follow1 it had to pass through the primary coils of all the transformers1 and the principles of a proper system of distribution were not present4 ,with the invention of the incandescent lamp the activity of inventors was given quite another direction4 ,the systems of electric lighting up to this time were not sufficiently advanced to permit even of a division#c of the electric light1 that is1 the ability to feed even a small number of lamps from one generator4 ,we shall only mention this invention so far as it helps to further the history of the transformer4 ,gramme made the earliest arc lamp that could be employed alone2 then followed ,jablochkoff1 as the first who carried out practically1 and with good results1 the use of arc lamps in series or in parallel arc with condensers4 ,siemens and ,halske then replaced the ,jablochkoff candles with their differential lamp1 which1 although not offering an opportunity for a good division of light1 was unexcelled in construction and manufacture1 pointing out the way for further progress in arc lighting4 ,this class of lighting was brought nearly as far forward as it is to-day by the introduction of continuous currents for this use by ,brush4 ,with the invention of the glow lamp quite other aims were placed in the foreground for the electrical world4 ,the incandescent lamp did not possess that unsteadiness of light which1 with arc lamps1 gave so much trouble to electricians4 ,the prominent qualities of the glow lamp offered opportunity for the solution of a problem1 such as gas had already solved half-a-century earlier1 namely1 the distribution of the electric light1 or1 more properly1 of the electric current4 ,for this1 the already known and generally employed methods of connection were no longer sufficient4 ,edison was the first who demonstrated that the series method of connection was not suitable for glow lamps2 at the same time he showed the advantages of parallel connection1 coming forward with a thoroughly well thought and worked out system of distribution4 ,by this means the change was made1 and1 from this time onward1 all inventors were obliged to suit their systems to the demand1 that each point of consumption must remain undisturbed by the variations of current which take place in the circuit4 ,marcell ,deprz has laid down in a work of his1#d the laws which make it possible to hold the points of consumption of electric energy independent of one another1 and1 excepting some inexactnesses which crept into his representation1 these laws have been almost all carried out in practice since that time4 ,the system of direct distribution to glow lamps had the one well-known serious drawback1 viz4 that it only allowed of limited employment1 because the cost of the leads1 with equal loss of energy1 increased with the square of the distance from the source of current4 ,it was therefore obligatory1 in order to carry the current economically to greater distances1 to seek new means and ways1 without rendering inefficient the only practical system of connecting incandescent lamps in parallel4 ,the experience which had already been gained in the economical carrying of high tension currents with arc lamps in series1 pointed out that high tension currents should be used1 and that in the secondary circuits of transformers fed by such a current1 consuming devices could be connected as might be desired4 ,sidenote3 ,h4 ,enuma1 #ahha4 ,haitzema ,enuma1 in the year #ahha1 was the first to go in this direction1 and took out a patent for the feeding of glow lamps by means of transformers4 ,he followed the principle of making each secondary circuit and each point of consumption independent4 ,the means to this purpose which he thought to employ were not practical1 and did not at all differ in substance from those of his predecessors4 ,his system is remarkable for his method of connecting the induction coils in the main lead1 i4e4 in series1 using the secondary currents from these coils to excite other coils from which tertiary currents were received1 and these again were further used to excite quaternary currents1 and so on4 ,this procedure stands on a level with that of the famed dynamo-electric chain of ,siemens and ,halske1 of which it has been asked1 8,to what purpose80 ,the peculiarities of the system of ,haitzema ,enuma become evident from the following extract from his patent3-- 8,solche 7nmlich die bekaunten7 ,induktionsrollen werden in den ,hauptstromkreis berall eingeschaltet1 wo der ,strom abgezweigt 767 werden soll2 und durch diese ,einrichtung erhlt zuletzt jede elektrische ,lampe1 oder jeder durch ,elektrizitt in ,betrieb gesetzte ,apparat seinen eigenen ,strom40 ,haitzema ,enuma had intended1 so far as this shows1 to connect the primary1 secondary1 tertiary1 c41 coils in series1 and the main lead being a closed circuit1 the ends were taken to earth4 ,the ends of the circuits of the secondary1 tertiary1 and further induced currents1 were also connected together1 or to earth4 ,sidenote3 ,gaulard and ,gibbs1 #ahhc4 ,the first who came forward with an industrial employment of the series system were ,gaulard and ,gibbs1 who1 in the year #ahhc1 placed before the public an installation of electric lighting in the ,royal ,aquarium in ,london4 ,illustration3 ,,fig4 #ah4 ,there were two such apparatus as shown in ,fig4 #ah1 which were connected in series1 and excited with #ac ampres from a ,siemens' alternating current dynamo4 ,the apparatus had the following construction3--,the induction coils1 a section of one of which is shown in ,fig4 #ai1 had three layers of primary wire1 and the secondary was wound in four divisions1 the ends of the wires of the divisions being led to a commutator4 ,fig4 #bj shows this commutator placed in the middle of four induction coils4 ,the ends of the secondary wires were connected to eight terminals on the upper plate of the apparatus1 from which the current could be led away from each pair1 or combined at will4 ,by aid of the commutator1 the number of coils in circuit could be altered as desired4 ,on the lower plate there was a second commutator1 which served the same purpose for the primary circuit4 ,illustration3 ,,fig4 #ai4 ,the core of the apparatus consisted of bars of insulated iron1 and by means of a rack could be raised or lowered in the coils for the regulation of the current4 ,both of these arrangements had been already long known4 ,in the same year another installation for the lighting of some stations on the ,metropolitan ,railway was taken in hand and carried out4 ,illustration3 ,,fig4 #bj4 ,the source of current was a ,siemens' alternating current dynamo of type ,w#j1 which was excited by a continuous current machine4 ,the potential was supposed to be #aejj volts and the current #aac ampres4 ,the main lead connecting the transformers in series was of #g wires of #ae mm4 diameter1 and was #bbi kilometres long1 having a resistance of #cj ohms4 ,three stations were supplied4 ,at ,edgeware ,road twelve coils1 with their secondary coils in parallel1 fed #cj glow lamps2 and other four coils1 also in parallel1 fed two ,jablochkoff candles4 ,in ,aldgate two coils supplied one arc lamp1 and twelve more coils #ce glow lamps1 each of #bj c4p4 and three of #dj c4p4 ,at ,notting ,hill there were #bb glow lamps and one arc lamp4 ,in this last installation coils were employed with their coils arranged after a somewhat different manner4 ,on a pasteboard or wooden cylinder of about #ej cm4 in height a cable was coiled in layers4 ,the interior of this cable consisted of a #d mm4 copper wire well insulated with paraffined cotton1 and around this1 parallel to its axis1 lay #f cables or cords1 each consisting of #ab wires1 also insulated with paraffined cotton 7,fig4 #ba74 ,the wire of #d mm4 formed the inductor through which the primary current was passed4 ,the six cables1 each of twelve strands1 formed the induced portion of the apparatus1 and the ends were connected to a commutator1 so that they could be used either in parallel or series4 ,illustration3 ,,fig4 #ba4 ,the methods of construction and connection used in these attempts by ,gaulard and ,gibbs did not differ in principle from those of their predecessors4 ,gaulard and ,gibbs also employed in these trials bi-polar induction apparatus4 ,the efficiency of such apparatus can only be comparatively small1 because the effects of magnetisation1 and therefore of induction1 are weakened to a great extent by the lines of force having to pass for the greatest part of their path through air instead of iron4 ,taking another view of such apparatus1 as they have a ratio of transformation of #a3a1 they must1 with the employment of high potential1 be connected in series4 ,undoubtedly ,messrs4 ,gaulard and ,gibbs have in their time claimed certain things as new and of their own invention1 namely1 the arrangement of several separate induction coils together1 the placing of the coils next to one another1 and the winding of the wires parallel4 ,these claims1 however1 have been condemned from all sides as unjustified4 ,the employment of several coils has already been mentioned as patented by the brothers ,bright on #bast ,october1 #aheb1 and was again later on discovered by ,poggendorf1 ,ruhmkorff1 ,foucault1 and others4 ,we have also shown1 on page #aa1 that the placing of the coils next one another had likewise been invented by the same men #cj years earlier4 ,the symmetrical arrangement of both coils1 the primary and secondary1 had also already been used4 7,see page #ah47 ,but when1 in spite of all this1 we find ,mr4 ,j4 ,k4 ,mackenzie#e maintaining that the ,fuller transformer was non-polar1 and further1 that the following improvements must be ascribed to ,messrs4 ,gaulard and ,gibbs1 viz43-- #a4 ,the reduction of the primary and secondary wire-resistance to a minimum4 #b4 ,the attainment of the greatest possible coefficient of induction with the lightest apparatus4 #c4 ,the symmetrical arrangement of both coils4 #d4 ,the proportioning of the coils1 so that the weight of metal in each is the same4 ,seeing this1 it must be thought that this gentleman either does or will not1 understand the subject4 ,then if ,gaulard has succeeded with his apparatus in obtaining some advantages as proposed in the above-mentioned clauses1 ,nos4 #a and #b1 these advantages can be obtained to a much higher degree with non-polar transformers4 ,this has been proven by ,prof4 ,ferraris4#f ,the improvements mentioned under ,nos4 #c and #d are only to be attained with bi-polar transformers after difficult and otherwise disadvantageous arrangements2 for instance1 the combination of the primary and secondary wires in a common cable1 or1 when the coils consist of ribbon wire1 by the winding of the one inside the other4 ,with non-polar transformers these improvements are already inherent4 ,the ,fuller transformer was just as much without poles as two horseshoe magnets are1 with their like poles laid together4 ,in all these systems with series connection of the transformers1 the intensity of the current in the primary circuit must be held constant in order that it may be possible for the induction apparatus to maintain the secondary electromotive force constant4 ,notwithstanding this1 constancy was not attained1 but only one cause of the variations annulled4 ,another cause of the variations of the difference of potential at the secondary terminals of the coil still remained2 this was the loss of potential due to resistance and self-induction1 which increased with the load4 ,the electromotive force of the secondary1 and therefore of the primary coils1 accordingly increases as the current in the secondary decreases4 ,when no secondary current is flowing1 the electromotive force in the primary and secondary coils is a maximum4 ,we have consequently this disproportion that the smaller the output of the apparatus the greater the energy consumed4 ,with the secondary circuit open and a constant exciting current1 the energy used could be as much as ten times as great as under full load4 ,the disadvantages of this system are apparent2 for1 putting aside the loss of energy arising from the disproportion between produced and consumed energy1 each change of load on the secondary circuit exerted a great influence on the primary circuit1 and again on the secondary circuits of the other coils in the main circuit4 ,all the transformer systems already described were intended1 as we see1 for subdividing the current1 and as fitting therefor we find the series method of connection universally brought forward4 ,with this method1 owing to a rise in electromotive force which was dangerous to the lamps1 c41 when only a part of those in the secondary circuit were extinguished1 it was compulsory either to run the induction coil fully loaded or quite empty4 ,thus1 when the number of lamps or other devices in use was varied1 a regulation of the current strength and uniform working was either quite impossible1 or only partly possible by unreliable and incomplete mechanical means4 ,on this account no one succeeded with this method in carrying out a rational distribution of current by means of induction coils such as are required by the widespread demands for electric current from a central station4 ,the first to point out the disadvantages of the series method of connection was ,rankine ,kennedy1 who had devoted himself wholly to the study of induction apparatus4 ,these disadvantages he published in an article in the 8,electrical ,review0 of #ith ,june1 #ahhc4 ,at the end of this article we find the interesting statement that transformers1 when not connected in the primary circuit in series1 as had been usual till then1 but in parallel1 form a self-regulating system of current distribution4 ,rankine ,kennedy expresses this in the following words3--8,in parallel arc1 however1 the secondary generator is a beautiful self-governing system of distribution40 ,at the same time1 however1 his article affords proof that the author then possessed only a limited comprehension of the physical facts concerned1 because he maintained1 for instance1 that the introduction of an induced counter electromotive-force in the circuit of an alternating current dynamo might constitute a means of regulation without loss of energy2 however1 it might be allowed1 that he meant by these words one of these elements which must be present in a really rational system of distribution with the use of transformers1 if it were not the case that at that time he was not aware both of the properties of transformers suiting them for such a connection as well as those which make them self-regulating in a system of distribution4 ,above all this he had at that time never thought of a transformer in the sense1 the word is used to-day1 that is1 as an induction apparatus1 which converts high into low tension currents4 ,this is quite clear1 as is seen from the end of the sentence before cited1 as he says1 8,but what about the size of conductors for such a system8 ,prodigious60 ,kennedy thought to all appearance that the parallel connection of transformers made possible self-regulation in the same manner as the simple direct parallel connection of incandescent lamps4 ,while at the same time he imagined that on account of the small resistance of each coil the resistance of the net of leads must nearly vanish1 therefore he concluded that the parallel connection of such induction apparatus as he had in his mind's eye was impracticable4 ,the apprehension of ,kennedy's ideas1 as we have here stated1 finds direct confirmation from the leading article in the 8,electrical ,review0 of #ith ,june1 #ahhc4 ,at the end of this leader the editors say1 that 8,mr4 ,kennedy's apparatus is an induction coil pure and simple40 8,messrs4 ,gaulard and ,gibbs will scarcely deny1 nor can they deny1 that the action of this particular construction of the coil is identical with that of his40 ,in this sentence it is distinctly stated that the construction of ,kennedy's induction apparatus is identical with that of ,gaulard and ,gibbs'4 ,kennedy accepted this statement in silence2 if it had been otherwise1 he would have protested in his next appearance in print4 ,in order to make possible the connection of transformers in parallel1 the advantages of which it may be said ,kennedy had augured1 there was still much wanting4 ,above all there was wanting the idea of a transformer as meant at present1 and an exact knowledge of its action4 ,f4 ,geraldy has expressed himself very suitably upon this point in the introduction to his report upon the trials made with the system of ,messrs4 ,gaulard and ,gibbs4#g 8,la distribution de l'lectricit comporte la solution d'un grand nombre de problmes4 ,il ne suffit pas de se dcider en principe et lorsqu'on a choisi la distribution en quantit 7en supposant mme1 que l'un des procds puisse tre appliqu d'une faon exclusive1 ce qui n'est pas certain71 lorsqu'on a trouv le moyen de rgler le gnrateur et les recepteurs conformment au mode choisi1 il reste encore lever quantit de difficults1 a crer et disposer beaucoup d'organes auxiliaires40 ,geraldy explained distinctly that it was not sufficient to determine only the method of connection1 but there were still a considerable number of obstacles to be surmounted before the object could be attained4 ,it has been a costly lesson1 before the properties of transformers were known1 which make them form a self-regulating system4 ,even in the year #ahhd do we still find ,messrs4 ,gaulard and ,gibbs on the same false track as previously4 ,it was in the ,turin ,exhibition where ,messrs4 ,gaulard and ,gibbs carried out their system upon a large scale1 and where they also succeeded in gaining the interest of technical circles1 and arousing general attention4 ,the transformers installed by ,messrs4 ,gaulard and ,gibbs in the ,turin ,exhibition were protected by the ,german patent1 ,no4 #bhidg1 and this time again their transformers were wound with equal primary and secondary coils4 ,the construction of the apparatus1 as already explained1 made it a necessary condition that the transformers be connected in series1 because only by this means could the high tension current be utilised4 ,it was a necessary corollary of this method of connection that the converting of the high potential of the primary circuit into low potential1 was performed1 not by the ratio of the number of turns in the coils of the transformers1 but in a certain manner by the subdivision of the electromotive force in the circuit4 ,illustration3 ,,fig4 #bb4 ,the special construction of the transformers used in the ,turin ,exhibition differed from the older apparatus in so far that both coils were formed of stamped out circular copper discs1 which were soldered together by projecting teeth4 ,the insulation was made of stamped-out paper discs4 ,both spirals were wound between one another4 ,the building up of such coils was effected in the following manner 7see ,fig4 #bb;,a73--,a red copper disc was first placed on the core1 then insulation1 upon this a black copper disc1 then again a red copper disc1 and so on4 ,like colours of copper discs were then soldered together at the projecting teeth4 ,in this manner there were produced two spirals running parallel with one another1 there only being one layer of coils4 ,the employment of such ribbon conductors had some advantages1 namely1 good use of the space at disposal for coils1 and rapid cooling through the projecting teeth4 ,they had1 also1 disadvantages1 the chief of which was1 that the conductors were of bare metal1 so that a fault in insulation could easily occur4 ,illustration3 ,,fig4 #bb;,a4 ,in fact1 several faults in the transformers in ,turin did arise from this cause1 the action of the coils being disturbed4 ,further attempts with similar coils were made1 the station houses of ,turin1 ,venaria1 and ,lanzo being lit for five consecutive hours4 ,the circuit was about #hj kilometres long1 the main lead being of chrombronze wire of #cg mm4 diameter4 ,at ,turin there were #cd ,edison lamps of #af c4p4 each1 and a sun arc lamp2 at ,lanzo there were nine ,bernstein lamps1 #af ,swan lamps1 a sun arc lamp1 and two ,siemens' arc lamps4 ,in the exhibition itself1 there were nine ,bernstein lamps1 nine ,swan lamps1 and a sun arc lamp4 ,in the ,figaro ,kiosk nine ,swan lamps were fed from a small transformer4 ,as already related1 the trials of ,messrs4 ,gaulard and ,gibbs' system at ,turin had aroused in the widest circles the liveliest interest1 and1 consequently1 the errors of the system soon became public4 ,thus we find in the technical literature of that time influential voices raised against the system1 and pointing out its disadvantages4 ,among others1 ,prof4 ,colombo read a paper during the course of the ,national ,exhibition at ,turin1 the subject being the system of ,gaulard and ,gibbs4 ,while doing sufficient justice to the good points of the system1 he also said that although it solved the problem of carrying the electric current to great distances1 it was in no way what it was represented to be1 and what it should be3 a system of distribution allowing the electric current from a distant central station to be led to meet the demands of any kind of consumer without any one of these interfering with the supply of current to any other4 ,he characterised these drawbacks sharply1 and very suitably1 by the remark1 that in the ,gaulard and ,gibbs system1 each consumer drew properly his supply of current from his transformer1 and not from a common network of leads always self-regulating1 as is the case in every large installation with continuous currents4 ,prof4 ,colombo satisfied himself with this reference to its disadvantages1 mentioning also what should be striven after to make the system a perfect one1 saying that the ideal electric lead system was one combining the advantages of the ,edison central-station with that of ,gaulard and ,gibbs4 ,prof4 ,colombo confined himself to these hints1 and he must acknowledge that the means leading to the attainment of this purpose remained still to be found out4 ,the reproduction of this lecture by ,prof4 ,colombo is placed before an article by ,deprz in 8,la ,lumire lectrique10#h in which latter the system of ,gaulard and ,gibbs is strongly criticised4 ,deprz showed that that system can have no claim to be new4 ,he points also to the wants of the system1 especially that of self-regulation1 stating that the means remain still to be discovered1 which would make possible the self-regulation of a system of distribution with transformers4 ,he also says that ,gaulard's system of distribution had not solved this problem1 and therefore could not be held to be practically useful4 ,we find the same view represented in an article by ,h4 ,roux1#i where he points to the enormous fluctuations which take place when the resistance in the secondary circuit is altered4 ,some of the figures vouching for his opinion we shall now reproduce4 ,they were taken by ,m4 ,pietro ,uzel1 in ,turin1 in an observational way4#aj ,the observations are only quoted so far that the ,watts ,i at the secondary terminals are still increasing2 were they continued further the damning fact would reveal itself that as the power put in increased1 the power given out would approach zero4 ,taking account of these fluctuations1 it is not possible to see how1 as ,mr4 ,roux says with justice1 a distribution of current by this system can be made in an efficient manner4 ,mr4 ,gaulard in his reply1 virtually assents to this article1 but adds1 that these variations could be prevented1 if the cores of the transformers be shifted either by hand or automatically4 ,both methods would be expensive1 and1 besides1 the automatic regulation would be unreliable4 ,external ,resistance ,no4 ,primary of ,secondary ,efficiency4 ,circuit4 ,secondary ,circuit4 ,circuit4 ,i ,i ,w4 ,i ,i #a #bcdabac #bhchd #abd #aejabjb #ahjcj #fceb #b #cadabac #chjhh #bjj #bdjabjj #bhhjj #gefb #c #ecjabac #fdbhi #chj #dejaahc #ecbce #hbha #d #gjjabac #hdiaj #eej #fejaage #gfbde #hihj #e #icjabacaabhji #gec #hgjaaehajjgdf #hica #f #ajgjabacabigia #ijj #ajbjaacaaaecfb #hhhh #g #abfjabacaeahch #ajfj #aaijaaacacbdgg #hfff #h #adejabacagehhe #abfj #achjajieaeaaaj #hece #i #aeijabacaibhfg #adae #aefjajgfafghff #hgjc ,it was at once recognised by all those interested in the subject1 that this system made possible a subdivision1 but by no means a distribution of current4 ,before proceeding further with the history of the development of the transformer1 let us for a little while take up the question1 what conditions are necessary for a practical and rational system of current distribution by means of transformers4 ,as we have already explained in another part of this paper1 the method of parallel connection1 i4e41 a system in which the difference of potential is held constant1 is alone suitable4 ,deprz maintained in his time that the difference of potential between the terminals of the source of current must be kept constant4 ,should the distribution be made on this principle1 the resistance of the network of leads must be very small1 in order that with full load only a very small loss of electromotive force may take place in the leads4 ,in the indirect system of current distribution1 consequently1 the tension at the secondary terminals of the transformers must also be maintained constant4 ,the question is now before us1 8,in what manner must the primary electromotive force vary to effect this80 ,consider an iron core1 having on two different parts round it1 two rings of wire4 ,this iron core may now be magnetised by bringing near to it in the line of its axis a permanent magnet4 ,on drawing the latter quickly away1 an electromotive force will be momentarily produced in both the wire rings1 and the electromotive force will be proportional to the number of the disappearing lines of force4 ,this number1 in consequence of the dispersion of the lines of force1 will be very different at different parts of the magnetised core4 ,the induced electromotive forces in the windings of the wire will also be different4 ,the equality of these electromotive forces1 which is so important1 can only be attained if all the windings are in relatively the same position with regard to the magnetic field4 ,the circuits of both coils being closed1 the one having a current flowing through it1 the other through a suitable resistance1 besides the condition mentioned in the last sentence1 another must be fulfilled2 this is1 the internal resistance must be practically zero1 i4e4 the difference of potential between the terminals shall equal to all intents and purposes the total electromotive force4 ,we have now to examine how far the already observed constructions of transformers fulfilled these demands4 ,a transformer in which the windings lie relatively in the same position to the magnetic field can quite well be bi-polar4 ,all that is necessary for this is that the coils be wound on to the core next to one another2 this is most simply managed in a transformer having a ratio of #a3a4 ,this law was first determined by ,maxwell4 ,the apparatus of ,strumbo shows such a method of winding already carried out4 ,thus it may be seen that of bi-polar transformers1 those which1 with regard to the constancy of the secondary tension1 are most suitable1 are quite useless on account of their ratio being #a3a1 although they are destined for the series method of connection4 ,the connection of proper transformers in parallel can only be made with such apparatus as1 notwithstanding their ratio of transformation1 possess windings having the same relative position to the magnetic field--this is only the case with non-polar transformers4 ,besides this quality of non-polar transformers1 their magnetic resistance is so low that the condition of very low internal resistance is easily fulfilled4 ,the following conditions of a self-regulating and economical system of current distribution with transformers result1 therefore1 from the foregoing explanations3-- #a4 ,the generator of current must give a great difference of potential as constant as possible at the terminals of the transformers1 and also independent of the number fed4 #b4 ,the transformers must convert the current of high electromotive force into a current of such electromotive force as may be desired4 ,the transformers must have a closed magnetic circuit 7that is1 they must be poleless71 in order that all the primary and secondary turns shall possess1 relatively to the magnetic field1 a like position1 also in order that the resistances of the primary and secondary coils shall be so small that they cause practically no loss of electromotive force4 ,through the fulfilment of both these conditions1 it is rendered possible to maintain the secondary tension constant by maintaining the primary tension constant1 indifferently whether it is regulated automatically or by hand4 ,to suit this1 the transformers must also be arranged into distributive stations of the second order1 and derived in parallel from the main leads4 ,sidenote3 ,zipernowsky1 ,dri1 ,blthy1 #ahhe4 ,in ,may1 #ahhe1 a system of current distribution meeting all the just-mentioned requirements was publicly brought out1 giving an illustration of a truly self-regulating system of current distribution4 ,this was the system of ,zipernowsky1 ,dri1 and ,blthy4 ,the first two patents concerning this system date from #ahth ,february1 #ahhe1 and are entitled1 8,improvements in the means for the regulation of alternating electric currents10 ,no4 #cd1fdi1 by ,carl ,zipernowsky and ,max ,dri1 of ,budapest2 8,improvements in the distribution of alternating currents10 ,no4 #cc1iea1 by ,max ,dri1 of ,vienna4 ,the third patent is dated #fth ,march1 #ahhe1 and is entitled1 8,improvements in induction apparatus for the purpose of transforming electric currents10 ,no4 #dj1dad1 by ,carl ,zipernowsky1 ,max ,dri1 and ,otto ,titus ,blthy1 of ,budapest4 ,the system described in these three patents was immediately afterwards brought forward in the three exhibitions of ,budapest1 ,antwerp1 and ,london 7,inventions ,exhibition71 arousing in technical circles a general and well-earned attention4 ,in the patent documents as well as in the earliest#aa articles in the journals concerning the system1 two special forms of transformers are described1 viz4 that consisting of an iron core with the wire outside1 and1 secondly1 that consisting of copper coils surrounded by iron wire4 ,the transformers shown in ,figs4 #bd to #bh belong to the last of these classes1 that in ,fig4 #bc to the first4 ,the fundamental principle upon which all these transformers are constructed is that the subdivisions of the iron core run perpendicularly to the copper wires4 ,transformers such as are shown in ,fig4 #be having a ring-shaped iron core wound with copper wire at first employed1 later the inventors used in preference the form represented in ,fig4 #bc4 ,illustration3 ,,fig4 #bc4 ,in all these forms the principle is generally adhered to1 that the magnetic resistance and the exciting power possess for each part of the length of the magnetic circuit the same value1 and thus the formation of poles with the resulting dispersion of the lines of force is avoided4 ,illustration3 ,,fig4 #bd4 ,this system procured for itself universal recognition1 but especially in the ,budapest ,exhibition4 ,there several exhibits within a radius of #a1cjj metres were lit from a common central station4 ,the several circuits were quite independent of one another1 and lamps could be extinguished or lit in any one of them without anywhere producing a change in the intensity of the light1 which could be perceived4 ,illustration3 ,,fig4 #be4 ,illustration3 ,,fig4 #bf4 ,illustration3 ,,fig4 #bg4 ,illustration3 ,,fig4 #bh4 ,illustration3 ,,fig4 #bi4 ,it was1 therefore1 in the year #ahhe that the problem of current distribution by means of transformers was solved in a truly practical manner4 ,the ideas which led the inventors to this thoroughly successful solution were then so unknown to practical and theoretical electricians1 that it was long ere they were understood and appreciated4 ,even in ,february1 #ahhf1 such an electrician as ,prof4 ,forbes maintained in his ,cantor ,lectures that the parallel connection of transformers was quite impracticable4 ,he believed1 namely1 that a connection such as shown in ,fig4 #bi was useless1 because the difference of potential at the generator diminished from the machine outwards1 but that a connection such as shown in ,fig4 #cj must be used4 ,according to him1 in a direct system of distribution each lamp should have a separate lead1 and having regard to the great number of leads which would thus be necessary1 he concluded that the series method of connection was the right one4 ,one would suppose that ,prof4 ,forbes was not aware of the weighty disadvantages of this method4 ,however1 that was not the case4 ,he proposed1 that with series connection the strength of current should be kept constant1 and that each transformer should have an especial regulating apparatus--the raising or lowering of the core2 which1 by the way1 is an arrangement impracticable in a well designed transformer4 ,such a regulating apparatus has lately been made automatic4 ,illustration3 ,,fig4 #cj4 8,this is10 says ,prof4 ,forbes1 8the last triumph1 which after a series of troublesome experiments has brought us year after year nearer to the solution of the difficulties40 8,i am not in a position to explain here the modus operandi10 he says further1 8but ,i have seen the apparatus working very satisfactorily40 ,illustration3 ,,fig4 #ca4 ,this apparatus has up till now not become known4 ,the assertion that the troublesome experiments had brought us year after year nearer to the solution of the difficulties1 is quite inappropriate4 ,just the opposite is the case2 they have taken us year after year further away from the solution1 until at last all was thrown overboard and a new commencement made4 ,profs4 ,rhlmann#ab and ,esson#ac also gave vent to their opinions against the connection of transformers in parallel4 ,in a like manner ,messrs4 ,gaulard and ,gibbs for some time after the ,zipernowsky-,dri system was known pleaded for their own method of connection1 until at last they were obliged1 on account of the unpleasant experiences at the ,grosvenor ,gallery in ,london1 to adopt the system of parallel connection1 which they then at once employed at ,tours4 ,there were1 up till very lately1 still many electricians who did not perceive the advantages of parallel connection1 just for the simple reason that they were ignorant of the properties of the non-polar transformer1 suiting the parallel system of connection for a rational system of distribution4 ,especially the one property of transformers remained unknown to the literature devoted to the subject up to the year #ahhe1 namely1 that in transformers properly constructed the relation between the primary electromotive force and that of the secondary1 remains unaltered notwithstanding any variations in the current taken out2 also that if the primary electromotive force be kept constant the secondary would likewise remain constant1 provided the transformer be connected in parallel4 ,it had taken #cj years1 until at last the way was found leading to the desired result4 ,we have already superabundantly explained that this direction was essentially different from that taken by all electricians until after ,gaulard's time2 that not only the methods of connection1 disposition1 and regulation of the system1 but also the construction of the transformers themselves had to be quite departed from1 and apparatus constructed which obeyed totally other laws to those of the earlier forms4 ,if indeed earlier inventors proposed for other purposes magnetically-closed induction coils1 the fame due to the birth of proper non-polar transformers1 in which the whole of the primary and secondary turns have a like position relatively to the magnetic-field1 first invented1 carried out1 and combined into a self-regulating system of current distribution1 belongs undoubtedly to ,messrs4 ,zipernowsky1 ,dri1 and ,blthy4 ,it would have been thought that after the direct distribution of current to glow-lamps had taken up a determined position1 it would not have been difficult to discover a self-regulating system of distribution with transformers4 ,however1 the fact shows this was not the case1 for after the ,edison lighting system was long known1 we find such electricians as ,haitzema ,enuma1 ,gaulard1 and ,kennedy1 experimenting with the series system of connection2 indeed the last of these even deters his colleagues from the attempt to run transformers in parallel1 because he openly held the opinion that this method of connection was impracticable4 ,we have here the development of current distribution by means of transformers1 as it completed itself in ,europe4 ,the ,american electricians however1 made the matter somewhat easier4 ,they quietly waited until the invention gave useful results in ,europe1 and then simply imported it4 ,the field to-day belongs to the parallel method of connection1 and after the installation in the alkali works at ,aschersleben was destroyed by flooding1 there only remains a single installation with series connection1 as far as we know2 this is that which was fitted up in ,tivoli near ,rome in the year #ahhf4 ,this installation however1 serves only to feed an invariable number of street-lamps1 and can therefore have no claim to the designation of an installation for the distribution of electric currents by means of transformers4 ,,london3 ,,printed ,,by ,,william ,,clowes ,,and ,,sons1 ,,limited1 ,,stamford ,,street ,,and ,,charing ,,cross4 ,,footnotes3 #a ,see also #8,scientific ,american1' #eth ,april1 #ahgi1 p4 #bab4 #b ,avernarius1 ,centralblatt fr ,elektrotechnik1 vol4 iii4 p4 #cbc4 #c ,at that time a customary and very characteristic expression4 #d ,comptes ,rendues1 #ahha1 p4 #hgb4 #e ,the #8,electrical ,engineer1' #agth ,feb41 #ahhh4 #f ,la #8,lumire lectrique1' vol4 xvii4 p4 #ade--adh1 #ahhe4 #g ,la #8,lumire lectrique1' vol4 x4 p4 #dif1 #ahhc4 #h ,la #8,lumire lectrique1' vol4 xiv4 p4 #de4 #i #8,electricien1' #gth ,march1 #ahhe4 #aj #8,natura1' #beth ,january1 #ahhe1 p4 #fj4 #aa ,elektricittsverteilung aus ,centralstationen1 ,system ,zipernowsky-,dri1 ,centralbl4 f4 ,elektrotechnik ,bd4 ,,vii4 ,s4 #dbb4 #ab #8,electrical ,review1' vol4 xvii4 p4 #aeg4 #ac #8,elektrotechnische ,zeitschrift1' ,september1 #ahhe4