,transcriber's ,notes3 ,text enclosed by underscores is in italics 7italics74 ,the whole number part of a mixed fraction is separated from the fractional part with -1 for example1 #b-a_/b4 ,additional ,transcriber's ,notes are at the end4 99 99 99 99 99 ,s,,ren ,,hjorth ,s,,ren ,,hjorth ,,inventor ,,of ,,the ,,dynamo-,,electric ,,principle ,,by ,,sigurd ,,smith ,c4 ,e41 ,m4 ,i4 ,f4 ,,published ,,by ,,elektroteknisk ,,forening ,,at ,,the ,,expense ,,of ,,the ,,carlsberg ,,foundation ,k,,benhavn ,,printed ,,by ,j4 ,,jorgensen ,,co4 7,m4 ,a4 ,,hannover7 #aiab 99 99 99 99 99 ,this pamphlet is published simultaneously in ,english and in ,danish1 and is distributed among interested institutions all over the world4 ,translated by ,f4 ,,sodemann1 ,c4 ,e41 ,m4 ,i4 ,f4 99 99 99 99 99 ,illustration ,handsworth1 ,birmingham1 ,feb4 #fth1 #ahea4 444 ,after this wonderful force has been discovered by ,your ,excellency1 it has been my pride and interest that also the utilization thereof should be originated by a ,dane4444 7,fragment of a letter from ,hjorth to ,h4 ,c4 rsted47 ,,preface4 ,since the ,life and ,works of ,sren ,hjorth1 the ,dane was published in the ,danish technical journal the ,elektroteknikeren1 in #aijg1 a statement concerning ,hjorth's rights of priority to the invention of the dynamo-electric principle has been sent to the leading foreign technical periodicals1 viz4 ,elektrotechnische ,zeitschrift1 ,l'clairage lectrique1 and ,electrical ,engineering4 ,as this statement still stands uncontradicted1 it seems reasonable to consider ,hjorth's priority rights to this principle to be generally acknowledged1 even in the great centres of civilization4 ,therefore ,i highly appreciated the courtesy of ,mr4 ,hjorth's heirs1 after the death of his step-daughter1 ,miss ,d4 ,ancker1 in the autumn of #aijh1 in offering me an opportunity to peruse the large collection of letters1 rough-copies1 drawings1 and sketch-books left by ,hjorth1 which threw new light on his interesting life and work4 ,where it was previously necessary to resort to guesswork alone1 we are now able to base our statements on established facts and to follow ,hjorth's train of ideas almost from his first1 to his last invention1 and to see where he has right and where he failed4 ,in the following pages1 an account will be given of the results of these recent researches in connection with what was previously known about ,hjorth4 ,charlottenlund #aiaa4 ,sigurd ,smith4 ,,contents4 ,page ,preface4 ,sren ,hjorth3 ,childhood and ,youth #a ,the ,railway #d ,electricity #g ,hard ,times #ah ,sources #bi 99 99 99 99 99 ,s,,ren ,,hjorth4 ,childhood and ,youth4 ,sren ,hjorth was born on the #acth of ,october1 #ahja4 ,he spent his childhood at ,vesterbygaard1 an estate rented by his father1 ,jens ,hjorth1 in ,jordlse ,parish1 north of ,tiss4 ,his mother's maiden name was ,margrethe ,lassen4 ,of their numerous children only two1 besides ,sren1 survived childhood4 ,the parents became early aware that their son possessed great mechanical genius4 ,he received his first education from the parish school-master4 ,after ,hjorth was confirmed1 his father leased the beautiful estate ,dragsholm1 in ,odsherred ,county1 where he remained for many years1 and after the death of his first wife1 he married baroness ,zytphen-,adeler4 ,though he did not have an opportunity of learning much in his childhood1 ,hjorth succeeded in his youth in passing an examination which admitted him to the ,bar4 ,later on he became the steward of ,bonderup ,estate1 near ,korsr1 but in this position he did not feel satisfied1 and in #ahbh he became a volunteer in the ,state ,treasury1 in ,copenhagen4 ,in #ahcf1 he advanced to the position of ,clerk of the ,exchequer and secretary4 ,although ,hjorth's occupation1 during the last #cj years of his life1 was mainly that of a civil engineer1 he always continued to be addressed as ,secretary ,hjorth1 and by this title he is still remembered by some of his surviving contemporaries4 ,hjorth's interests while at the ,treasury were not concentrated solely on his work there4 ,mechanical problems always fascinated him4 ,it is told that1 during this period1 he made all kinds of experiments at ,dragsholm1 and1 among other things1 he constructed a thrashing-machine4 ,in #ahcb he constructed a rotary steam-engine1 which was made by ,schidt1 a mechanic residing at ,st4 ,annae ,plads1 and1 upon ,hjorth's application1 it was bought by the ,king for #ejj rixdollars in notes4 ,the ,king donated it to the newly founded ,polytechnic ,institute1 this being the place where it might best be utilized and where this original domestic invention might most suitably be placed4 ,the same year1 ,hjorth described in ,ursin's ,magazines for ,artists and ,artisans a steam-car1 invented by him and adapted to be propelled by means of the rotary steam-engine4 ,so ,hjorth once more made a petition to the ,government for a subvention of #bjjj to #bejj rixdollars to assist in the practical manufacture of this car4 ,the decision on this application was postponed1 however1 at the suggestion of ,professors rsted1 ,zeiss and ,forchhammer1 because ,hjorth had not yet finished the installation of the boiler for the first steam-engine at the ,polytechnic ,institute4 ,hjorth did not succeed in making the engine work1 as it was not made with sufficient accuracy4 ,the sum for which the car was to be made1 was never granted1 as petitioned for1 although ,hjorth had given up using his rotary engine for it2 and the car itself was probably never built4 ,at that time1 the use of steam-cars on the country roads attracted great attention in ,england1 and many different constructions appeared4 ,in #ahcd ,hjorth1 aided by subventions from the ,rejersen ,foundation and the ,government1 went to ,england1 in order to acquaint himself with the use of these steam-cars on high-roads and railroads4 ,during these years he very actively investigated the use of steam-power1 especially as a means of propulsion for vehicles and ships4 ,with admirable interest and diligence he studied the steam propelled road-carriage1 and for a long time he considered that to be the future means of conveyance4 ,although he did not succeed in getting his own steam-carriage put to practical use1 he made many experiments on a steam car1 and ,i am told by one of his passengers that on the level streets of ,copenhagen and ,frederiksberg all went very well1 but the carriage could not climb ,valby hill4 ,during these years1 ,hjorth also attended the lectures at the ,polytechnic ,institute1 and he was especially interested in rsted's lectures on the physics of the globe1 and on electricity and magnetism4 ,notwithstanding his unsuccessful experiments with the rotary steam-engine1 ,professors rsted1 ,zeiss and ,forchhammer had to give him a warm recommendation1 when he made a petition to the ,ministry in order to get his expenses refunded by the ,government4 ,they mentioned his indefatigable zeal1 his great diligence1 and the considerable expense borne by him in the pursuit of his researches4 ,the numerous and expensive experiments absorbed all the money ,hjorth could procure3 not only his salary was spent1 but also such funds as he was able to raise among his friends4 ,the ,railway4 ,in #ahci ,hjorth made a journey to ,england1 ,france and ,belgium4 ,by that time1 he seems to have come to the conclusion that steam-carriages running on rails1 are preferable to steam-carriages running on the high-road1 at any rate he mainly studied locomotives and railroading during this journey4 ,after his return to ,denmark1 he spent some years as manager of ,marschall's piano factory1 though still at work with his railroad schemes1 and in #ahdj he happened to find a man named ,schram1 a book-keeper1 who shared his interests and was able to assist him in the realisation of his ideas4 ,in #ahdj1 these two men published a detailed calculation of the probable revenues and expenses of a railroad between ,copenhagen and ,roskilde4 ,this project1 however1 did not arouse any interest1 and people were mostly inclined to smile at the idea1 and it appeared impossible to induce competent men to take1 any interest in the scheme1 much less to invest money therein4 ,then1 in #ahda1 they applied to the young ,industrial ,association which body referred the case to its special committee of commerce4 ,even this committee did not seem much inclined to listen to ,hjorth's and ,schram's proposition1 but their undefatigable energy finally succeeded in persuading the committee of commerce to convoke a large meeting to be held on the #bdth of ,march4 ,here it was decided to make an application to the ,government for the surveying of the proposed railroad line and1 to the surprise of many1 the petition was granted4 ,hjorth1 possessing distinctive agitatory faculties1 showed great activity1 delivering lectures and exhibiting models1 and tried thereby to excite interest in his schemes4 ,his contemporaries describe him as a sociable man of a winning and lovable disposition and possessing a certain persuasive power4 ,he was well liked by his friends as well as by his many casual acquaintances4 ,in #ahda both ,hjorth and ,schram were elected members of the ,board of ,representatives of the ,industrial ,association1 and from #ahda to #ahdc ,hjorth was the vice-president of the association4 ,now there began to be some sympathy for their cause1 and the ,board of ,representatives of the ,industrial ,association showed a willingness to follow the sub-committee elected1 consisting of the two motionists and ,lector1 7later ,professor7 ,wilkens of the ,polytechnic ,institute4 ,the strenuous efforts of this sub-committee resulted in the ,industrial ,association submitting1 in ,january #ahdc1 an application for a franchise to form a stock-company for the purpose of building a railroad from ,copenhagen1 by way of ,roskilde1 to a sea-port on the western coast of ,sealand4 ,this franchise1 was granted1 for a period of #ajj years1 and on the #afth of ,april #ahdd the ,industrial ,association issued a public invitation to take stock in a company whose stock capital was to be #a-a_/b million rixdollars1 a very considerable sum for those times4 ,as early as in the beginning of ,may1 most of the stock was taken--mainly in ,hamburg4 ,while the confidence in a scheme of this kind was but slight in ,denmark1 the speculation in railroad stocks was nearly culminating at the stock-exchanges of ,germany and ,england2 as a matter of fact1 it became near being a swindle4 ,the ,sealand ,railroad ,company was founded on the #bnd of ,july #ahdd1 and ,hjorth became its first technical director1 while ,schram became its first general manager4 ,the ,industrial ,association received #aejjj rixdollars for the franchise1 and from this sum it paid #cjjj to ,hjorth and ,schram4 ,in #ahdc1 ,hjorth was unanimously elected president of the ,industrial ,association4 ,in #ahde1 he had to resign this office1 but as it appeared very difficult to concentrate the votes in favour of a new president and vice-president1 ,secretary ,hjorth1 to meet the general demand1 accepted the vice-presidency1 which office he then held for a year4 ,in the meantime1 the railroad company had finished the construction of its first piece of road1 from ,copenhagen to ,roskilde1 and this was opened for traffic on the #bgth of ,june #ahdg1 some days before the time limit fixed4 ,even at that time it was decided1 owing to ,hjorth's influence1 to extend the road to ,korsr4 ,the cause of the delay in commencing this work was the railroad crisis which had just broken out in ,germany and ,england1 making it impossible to obtain money for the construction of railroads4 ,this road1 therefore1 was not constructed until the government1 in #aheb1 guaranteed an interest of #d on the capital invested4 ,hjorth retained his position for about #d years1 and concerning this period he writes3 ,all the great difficulties and obstacles to be surmounted during the construction of the road influenced my health to such a degree that ,i broke down and was forced to abandon my position as technical director of the railroad before the expiration of my term of office1 in order that ,i might take a water-cure at ,klampenborg4 ,after he had1 to some extent1 regained his health there1 and another board of directors had been elected1 he made a travel to ,england which turned out to be of such great importance that we will describe it more fully in the following4 ,electricity4 ,after ,faraday1 in #ahca1 had discovered how an electric current might be produced by means of a magnet1 many people busied themselves by trying to put this invention into practical use1 and numerous attempts were made to construct electro-magnetic and magneto-electric machines for useful purposes4 ,no wonder that these efforts attracted ,hjorth's attention1 and1 as early as #ahdb1 he had drafted an electro-magnetic machine1 consisting of a stationary circle of magnets1 whose poles were directed against the poles of a moveable circle of magnets4 ,in #ahdc this sketch was deposited with the ,royal ,scientific ,society1 but the sketch itself1 as well as the explanation belonging to it1 are very incomplete4 ,in the month of ,april1 #ahdh1 ,hjorth made a petition to the government for a subvention of #bjj rixdollars1 in order that he might go to ,england to get an electro-magnetic machine#a designed by him1 made there4 ,hjorth had noticed that1 in a piece of iron encircled by an electric current1 the magnetism only to a certain extent would increase1 with the strength of current1 there being a point of saturation for the iron4 ,when this point has been reached1 it will be of no use to increase the intensity of the current1 since the magnetism will not increase any further4 ,on the basis of this observation1 ,hjorth had constructed his machine1 but he had confided the details thereof only to ,professors rsted and ,forchhammer4 ,in the report on ,hjorth's petition made by these two professors to the ,board of ,trade1 they1 curiously enough1 take exception to the above-mentioned observation by ,hjorth1 while its correctness will now be acknowledged by any electrician4 ,these professors1 however1 advised that ,hjorth's petition should be granted1 using this liberal argument1 worded by rsted3 ,regarding the petitioner's new electro-magnetic machine1 we must state that we find it quite ingenious1 and although we are not convinced that it will produce remarkable effects1 we should consider it useful to have a working model executed4 ,having during so many years worked for this case1 the petitioner might perhaps1 by the execution of such a model1 be enabled to make some further invention1 which would bring him nearer to the goal4 ,indefatigable zeal has often accomplished its purpose1 where science had to declare the means at first used1 to be entirely inadequate1 but where1 by continued work1 entirely different means1 previously unknown to the inventor1 were found4 ,inasmuch as the sum of #bjj rixdollars asked for is so small1 we find it advisable to grant the subvention4 ,still we cannot refrain from remarking that the petitioner's machine may just as well be made here as at any other place4 ,thus the discoverer of electro-magnetism cleared the road which was to lead to the most beautiful application of electro-magnetism1 that application which1 before all others1 has been of radically reforming importance during the last half century1 thereby throwing double splendor on rsted's name4 ,soon after his arrival at ,london1 in the summer of #ahdh1 through a firm which he knew from an earlier period of his life1 ,hjorth made the acquaintance of a nephew of ,bramah1 the renowned mechanician and inventor of the ,bramah-lock4 ,hjorth's invention was then laid before a friend of ,bramah's1 a civil engineer named ,gregory1 who had made the study of magnetism his specialty4 ,gregory at once persuaded ,bramah to bear the expense of making a machine1 and of securing patents in ,england and several other countries1 on condition that the expected profits should be divided between him and ,hjorth4 ,later on1 ,b4 ,taylor and ,normann ,innis were taken in as partners1 paying together #ajjj1 and then ,charles ,stovin 7#fjj7 and ,robert ,broad1 of the ,henley ,iron ,works 7#ejj74 ,two machines were now made1 according to ,hjorth's directions1 by the firm of ,robinson ,sons1 ,pimlico1 ,london4 ,one of these is shown in ,fig4 #a1 and is apparently quite an ingenious imitation of the steam-engines of those days4 ,c is a movable1 ,a a fixed electro-magnet4 ,their peculiar shape1 involving several conical pins fitting into corresponding cavities1 was thought to be advantageous for the distribution of the effect of the magnetic force over a longer stroke4 ,the piston ,c1 reciprocating up and down1 drives a crank shaft having two opposite cranks4 ,to either of the cranks there is a corresponding group of magnets4 ,an eccentric fixed on the shaft1 moves a slide valve1 alternately closing the circuit of one or the other of the two groups of magnets4 ,when the one piston is at its lowest position1 the circuit of the other group of magnets is closed1 and its piston is attracted1 until it reaches its bottom position2 then the current is shifted1 and the other piston attracted1 etc4 ,in order to avoid the formation of sparks at the circuit breaker1 an ingenious device was provided1 closing the current of one group of magnets1 immediately before that of the other one was broken4 ,the first machine was made with a #d inch stroke1 the next one with #ac-a_/b inch stroke4 ,the magnetic attraction per square inch of the piston1 had about the same magnitude as the pressure per square inch in the low pressure steam-engines of those days4 ,the patent application was filed in ,london as early as in ,october #ahdh1 and it was granted on the #bfth of ,april #ahdib4 ,on the #bast of ,september1 the same year1 ,hjorth obtained a fifteen year monopoly in the kingdom of ,denmark1 to manufacture machines1 utilizing electro-magnetism as motive power in the above described manner4 ,illustration3 ,fig4 #a4 ,hjorth's ,electromotor4 ,the larger of the machines here referred to was shown in action to several technical experts1 and created considerable sensation1 especially on account of the great length of stroke attained--#ac-a_/b inches--and the uniform motion of the machine4 ,the machine is mentioned in ,mining ,journal1 for the #eth of ,may1 and #afth of ,june #ahdi1 and an extract of these articles is published in the ,flyveposten for the #crd of ,july the same year4 ,hjorth was invited to show the machine at the ,royal ,society1 and at the annual meeting of the ,society of ,civil ,engineers1 of which he was a member4 ,it was exhibited at the ,universal ,exhibition in ,london1 in #ahea4 ,in the catalogue it was highly commended1 and it received the only prize-medal awarded to electrical machines4 ,there was1 however1 one essential obstacle to the practical use of this machine1 namely the lack of means for cheaply producing electricity in the quantities required by the electromotor4 ,wet batteries were expensive to use1 and if the machine were to become useful in practice1 a powerful dry battery would be a necessity4 ,most of the then known machines producing electricity1 were fitted with permanent steel magnets1 and as the point of magnetic saturation of steel is low1 these machines were unable to produce any considerable quantities of electric energy4 ,hjorth therefore imposed upon himself the task of building a dry battery4 ,his sketch-book from #ahea is full of new schemes for such batteries and improvements on those already existing 7,woolrich's1 ,elkington's and ,paine's74 ,from this it appears1 among other things1 that he was fully aware that1 when the spools suddenly entered or left the field1 difficulties would arise in the commutation1 and he therefore improved the machine by bending the field magnets1 obtaining thereby a gradually increasing and decreasing field1 the same thing which is1 nowadays1 attained by using pointed or obliquely cut pole-shoes4--,it would be very tempting to study more closely these sketch-books with their neatly colored drawings1 showing how many different ideas have been fostered by him1 before the actual production of the first dynamo1 in #ahed4 ,most of the descriptions and notes have been written in the ,english language1 which he used almost as readily as his native tongue4 ,on the #ast of ,may1 #ahea1 ,hjorth writes in his sketch-book1 beside a sketch of a machine having copper discs for armature conductors and cast iron electro-magnets3 ,by passing the current on the said way round the ,electromagnets1 these will of course be excited in proportion to the strength of the same1 and the more they are excited1 the more will the discs be influenced by the magnets1 a mutual action thus taking place4 ,so it appears that ,hjorth1 as early as on the #ast of ,may #ahea1 with perfect clearness1 has pronounced the dynamo-electric principle4 ,under the date of ,june #bdth1 #ahea1 we find sketched out another beautiful idea for the construction of a dynamo4 ,it must be regretted that this machine has not been executed1 as it would certainly have proved superior to his dynamo of #ahee1 which has many points in common with this project4 ,fig4 #b shows a reproduction of this page of the sketch-book4 ,there is no descriptive text to this sketch1 only at one side of the drawing1 these very significant words are written3 ,magneto-,electric arrangement with mutual action4 ,all the six powerful held magnets are of cast iron1 and they are wound so as to be magnetized by the current1 produced by the dynamo itself#c4 ,illustration3 ,fig #b4 ,facsimile of a ,page of ,hjorth's ,sketch ,book1 ,june #bdth #ahea4 ,in ,november1 #ahea1 ,hjorth returned to ,copenhagen1 and here he continued what he had commenced in ,england4 ,in ,may1 #aheb1 he deposited with the ,society of ,sciences some papers1 signed by ,professors ,scharling and ,forchhammer in ,december1 #ahea4 ,these papers contain two descriptions1 written in ,english1 and two drawings of dry batteries4 ,these consist of #c or #d circular rows of vertical steel rod magnets1 placed one above the other1 and disposed round a vertical shaft1 carrying #b or #c circular rows of armatures4 ,each armature consists of a piece of soft iron1 and is wound with a strip of copper1 in a special manner4 ,there are1 in each row1 as many armatures as magnets4 ,the hollow shaft1 as well as the magnets1 which are fitted with shoes of soft iron1 are wound1 and encircled by the current produced in the armatures4 ,with regard to the magnetic arrangement1 this machine comes very near to the one patented by ,brett in #ahdh1 and it will be noticed that it cannot be said to be constructed according to the dynamo principle1 as the mutual action plays no important part1 the magnets being permanent steel magnets1 hardly adapted to receive much extra magnetism by the current of the machine4 ,hjorth points out1 as the novel feature of these machines1 the division of the steel magnets into many small ones1 with an armature corresponding to each magnet4 ,hereby he claims1 for the same weight of the steel magnets1 a larger capacity of the machine than if he had used fewer1 but larger steel magnets#d4 ,the machine is fitted with a commutator for direct current4--,in ,march1 #ahed1 the sketch-book contains another sketch of a dynamo1 with clear indication of the dynamo principle1 approximately as it was patented on the #adth of ,october the same year#e4 ,this sketch is reproduced in ,fig4 #c4 ,the machine has two permanent cast iron magnets and two electro-magnets4 ,the armature cores are fitted with oblique pole-shoes4 ,the description is very brief and contains the same as the patent specification4 ,illustration3 ,fig4 #c4 ,facsimile of a ,page of ,hjorth's ,sketch ,book1 ,march #ahed4 ,in #ahec ,hjorth negotiated with a certain ,dr4 ,watson1 who had constructed a dry battery by means of which ,hjorth had meant to drive his electro-magnetic machine4 ,the object of their negotiations was to buy out ,hjorth's above-named partners1 and to form a new company for the purpose of exploiting the above-mentioned two machines4 ,the partnership1 however1 was not realized1 and in spring of #ahed1 ,hjorth himself commenced to have a #c ,,hp battery built in ,copenhagen4 ,the machine was fitted with cast iron magnets1 and in all probability it was similar to the project of ,march #ahed1 and agreed with the patent of ,october1 the same year4 ,this patent specification reads as follows3 ,the main feature of this battery consists in applying one1 two1 or several permanent magnets ,a1 of cast iron1 and shaped as shewn in the drawing 7,figs4 #d and #e71 in connection with an equal number or more electro-magnets ,b1 shaped as indicated in drawing1 in such a manner that the currents induced in the coils of the revolving armatures are allowed to pass round the electro-magnets2 consequently1 the more the electro-magnets are excited in the said manner1 the more will the armatures ,c be excited1 and the more electricity of course induced in the respective coilings2 and while a mutual and accelerating force is produced in this manner between the electro-magnets and the armatures1 an additional or secondary current is at the same time induced in the coiling of the electro-magnets by the motion of the armatures1 the said current flowing in the same direction as that of the primary current1 after having passed the commutator4 ,the direction of the current induced in the coils of the armatures will1 of course1 be reversed according to the change of the respective polarities1 and the commutator ,d is therefore applied for the purpose of causing the current to flow constantly in one direction4 ,then follows a description of the commutator of the dynamo4 ,finally the pole-shoes1 or false poles1 provided on the magnets as well as on the armatures1 are mentioned4 ,he points out that the false poles have on the side of attraction1 a long straight edge1 as distant from the centre as possible1 while on the side of separation1 either one has a sharp point1 nearer to the axis of revolution1 all with a view to avoid reactionary currents1 and at the same time to facilitate the motion of the armature4 ,while steel magnets also may be applied instead of cast-iron magnets1 the permanent magnets may be coiled like the electro-magnets1 which also will serve to make them more permanent4 ,illustration3 ,fig4 #d4 ,hjorth's ,dynamo #ahed4 ,illustration3 ,fig4 #e4 ,hjorth's ,dynamo #ahed4 ,fragment of the ,patent ,drawing4 ,from the above-named sketch-book notations1 and the patent specification1 it will be seen that ,hjorth1 during the years #ahea-ed1 has repeatedly pronounced the dynamo principle with perfect clearness1 and that he has utilized it in several projects4 ,it is worth noting that ,hjorth's so-called permanent magnets are of cast iron4 ,this shows that ,hjorth has known of remanence1 or permanence4 ,he has known that cast iron always possesses some slight magnetism1 either induced by the earth magnetism or as a remnant--remnant magnetism--left over from its being magnetized in a coil4 ,it has heretofore been assumed that ,siemens was the first to call attention to this property of iron1 in his paper in the transactions of the ,royal ,society1 of the #adth of ,february1 #ahfg4--,thus ,hjorth used this weak remanent magnetism in the large cast iron magnets to produce the initial current in the dynamo1 which then excites itself4--,at the end of the patent specification1 ,hjorth points out that the remanent magnets may also be coiled 7compare ,fig4 #b71 and thereby he comes closer to the later dynamo constructions4 ,hjorth is quite right1 according to the patent specification1 in giving the pole-shoes such a shape that the armature is gradually demagnetized1 and in stating that the object of this is thereby to avoid reactionary currents1 and consequently the formation of sparks2 while he is mistaken in believing to be able to facilitate the motion of the armature by giving the pole-shoes a certain special shape1 because in that case1 the machine would be a perpetuum mobile4 ,together with the above-mentioned dynamo1 ,hjorth had an electromotor made in ,copenhagen1 essentially similar to the one exhibited in #ahea4 ,when in the autumn #ahed the machines were finished1 ,hjorth was called back to ,england1 in order to continue the work on his inventions4 ,it is not known whether the machines were sent to ,england or not2 at any rate they aroused some interest there1 and he had a new and larger dynamo built by ,messrs ,malcolm ,campbell2 of ,liverpool1 #g ,india ,buildings1 at the expense of ,malcolm and others4 ,this machine was patented in #aheef1 and is shown in ,fig4 #f1 which is reproduced from a photograph4 ,here1 too1 the dynamo principle has been followed1 but each electro-magnet is composed of one solid and one tubular electro-magnet1 the latter enclosing the former1 the two together forming a so-called cup magnet1 a construction which has also been used by later inventors4 ,hjorth describes the action of the battery as follows3 ,the permanent magnets acting on the armatures1 brought in succession between their poles1 induce a current in the coils of the armatures1 which current1 after having been caused by the commutator to flow in one direction1 passes round the electro-magnets1 charging the same and acting on the armatures4 ,by the mutual action between the electro-magnets and the armatures1 an accelerating force is obtained1 which in the result produces electricity greater in quantity and intensity than has heretofore been obtained by any similar means4 ,at the same time1 ,hjorth allowed the dynamo patent of #ahed to lapse1 it being merely a provisional patent4 ,illustration3 ,fig4 #f4 ,hjorth's ,dynamo #ahee1 from an old ,photograph4 ,together with the dynamo patent of #ahed1 ,hjorth secured a provisional patent on an improved electromotor#g1 and together with the dynamo patent of #ahee1 he obtained the complete patent on the above mentioned electromotor1 as well as on another construction thereof#h4 ,the former consisted of hollow1 horizontal electro-magnets 7cylinders71 being of a special shape inside1 adapting them to give to an electro-magnetic piston1 reciprocating within them1 a long and steady stroke4 ,by means of a crank1 the stroke was transformed into a rotary motion4 ,the other electro-motor consisted of wheels1 with protruding teeth1 which were set in rotary motion by the teeth being attracted into hollow electro-magnets4 ,,footnotes3 #a ,according to the usual terminology of those times1 an electro-magnetic machine means a machine driven by electricity1 an electromotor1 while1 on the other hand1 a magneto electric battery1 or a dry battery is a machine for producing electricity4 #b ,specification of ,patent ,no4 #abbie1 #ahdh4 #c ,after the publication of my first treatise in the ,elektroteknikeren1 for ,february #aijg1 various parties have objected that ,hjorth1 in his dynamos1 did not use the dynamo principle in its purest form1 as he had one large1 unwound1 cast iron magnet4 ,on the contrary1 the above-mentioned leaf of his sketch-book shows that ,hjorth1 as early as in #ahea1 has used the dynamo principle in its purest from--exactly the same as used by ,siemens in #ahfg--;as all the field magnets have been wound cast iron magnets1 and the initial current is induced by the remnant magnetism of these magnets4 ,s4 ,s4 #d ,this is correct1 as long as he uses armatures with but a single winding1 because1 in that case1 the number of armature windings is proportional to the number of steel magnets4 ,whereas ,hjorth is mistaken1 when in #ahfg he makes the same statement about a machine1 where nothing prevents the armature from being fitted with a great number of windings4 #e ,specification of ,patent ,no4 #baih1 #ahed4 #f ,specification of ,patent ,no4 #hjf1 #ahee4 #g ,specification of ,patent ,no4 #baii1 #ahed4 #h ,specifications of ,patents ,no4 #hjg and #hjh1 #ahee4 ,hard ,times4 ,in ,may1 #ahef1 ,hjorth returned from ,england1 disappointed4 ,it will be noted that through the electro-motor ,hjorth was led to occupy himself with the dynamo machine4 ,the dynamo was built in order to produce motive power for the motor4 ,all the time he was working on these two inventions1 it was his firm belief that if he could make the dynamo drive the electro-motor1 he would be able to attain a substantial saving in power1 get much more power out of the electro-motor than was consumed in driving the dynamo4 ,the machines would1 as it were1 run automatically4 ,he could not understand1 why ,dr4 ,watson was sceptical with regard to this manner of battery action4 ,he intended to install his machines in ships and locomotives1 which would then be propelled with a minimum consumption of power4 ,in short1 the combination of dynamo and electro-motor imagined by ,hjorth was to be a perpetuum mobile4 ,it has certainly been the great disappointment of his journey to ,england1 that this scheme failed4 ,on reading about this mistake1 one is inclined to base the judgment of ,hjorth upon assumptions belonging to the present time4 ,but this would be a great injustice to him4 ,the axiom that the quantity of energy in nature is unalterable1 and consequently a perpetuum mobile an impossibility1 has1 as it were1 been imbued by our own generation with the mother's milk4 ,not so with ,hjorth4 ,not until the forties of the last century1 did ,mayer1 ,joule and ,colding1 the ,city ,engineer of ,copenhagen1 set forth their theories about the permanency of energy1 and about the convertibility of heat into mechanical activity1 and of the latter into heat again4 ,these theories1 however1 were very slowly accepted1 even by scientists4 ,it is1 therefore1 no wonder that a man like ,hjorth1 having no special scientific training1 could not easily digest the new theory and ,hjorth did not have any instinctive sensation of having entered upon a hopeless and impossible track4 ,on the contrary1 he imagined the new wonderful form of energy to conceal unestimable possibilities which he had only to wrest from nature4 ,though ,hjorth was thus ship-wrecked on his favourite idea1 he nevertheless discovered new land1 fertile for coming generations4 ,his intrepid zeal guided him1 as rsted had anticipated1 in spite of his lack of scientific education1 on to the road leading to the splendid results of this day4 ,none of ,hjorth's original partners participated in the manufacture of his latest machines1 and possibly this was due to his above-mentioned erroneous idea4 ,only one of his ,english friends1 ,wm4 ,macredie1 of ,melbourne1 maintained his attachment to ,hjorth and his confidence in him to the last4 ,he was always very interested in ,hjorth's schemes1 and1 besides1 he shared his religious creed4 ,hjorth was very anxious as to his future4 ,when he returned from ,england1 he stood quite destitute and felt depressed by poverty4 ,his health was not of the best1 and his formerly so neat hand-writing had become unsteady4 ,he received1 shortly after his return1 a communication from his ,english partners that they wished to have the dynamo patented in ,denmark and ,france1 which showed that they had faith in this machine1 but nevertheless these were hard times for ,hjorth4 ,the dynamo remained for some time with ,malcolm1 in ,liverpool1 and negotiations for its sale were several times entered into1 but were without results4 ,it was tested on several occasions1 but these tests proved that it could not yield as much as might be expected from its size4 ,the uncoiled magnets1 which were originally of cast iron1 were replaced by more powerful steel magnets4 ,upon the whole1 this dynamo had a rather eventful existence1 for first every other magnet pole was removed 7see ,fig4 #f71 and then it was proposed to rewind the magnets4 ,in ,may1 #aheg1 it was donated to the ,polytechnic ,institute1 ,regent ,street1 in ,london4 ,among the papers left by ,hjorth1 there are a daguerreotype and a photograph of this machine1 7from which the accompanying ,fig4 #f is reproduced74 ,notwithstanding a thorough search of the ,london museums1 it has been impossible to trace this machine1 which is said to have been seen in ,london during the nineties4 ,hjorth was now compelled to find a new means of earning his livelihood1 and to make new connections4 ,in #aheg1 he became the representative of ,cyclop's ,steel ,manufactory1 ,charles ,cammell1 of ,sheffield1 and in #ahei1 he applied for and obtained a licence as a translator of ,english in ,copenhagen4 ,finally he had a kind of engineering and patent office1 assisting strangers in obtaining monopolies1 and doing work for new railroads1 bridges etc4 ,in the beginning of the sixties he caused a research to be made concerning the use of coals from ,hornholm and ,silkeborg1 and the use of peat for briquettes4 ,in ,april1 #ahfj1 he applied to the government for a position1 enabling him to work for the building of new railroads in ,denmark1 and at the same time he referred to his previous merits in that direction4 ,as he had not1 within a year thereafter1 received any position1 he made a petition for a yearly pension1 in case such a position could not be given to him4 ,as the idea of building the ,sealand railroad1 as well as the general location of this road1 is mainly due to ,secretary ,hjorth 444 and further more1 no small share in the completion of the undertaking is due to him1 it was proposed1 on the budget for #ahfa-fb1 to grant a pension to ,hjorth4 ,that year and the following ones1 until his death1 he received #ejj rixdollars4 ,during these years1 ,hjorth lived at #aj ,nrrebrogade4 ,in #ahde1 he married ,vilhelmine ,ancker1 ne ,hansen 7born on the #bgth of ,march1 #ahje71 the widow of the farmer ,diderick ,ancker1 of ,lille ,egede1 and thereby he became the step-father of two daughters4 ,this marriage was childless4 ,this carefully dressed little man#i in top-hat and high-heeled shoes1 was well known1 and very well liked in many circles4 ,he was always amiable and willing to help1 and it is known that he has1 at great personal sacrifice1 assisted young artisans who were in hard luck4 ,in society he attracted attention by his power of fascination and by his universal knowledge4 ,on ,sundays he was regularly seen directing his steps to ,st4 ,john's church1 where1 for many years1 he was a member of ,rev4 ,frimodt's congregation4 ,during the period of depression above described1 ,hjorth could naturally not very well afford to occupy himself with experiments1 nor had he much time4 ,still1 in #aheg1 he secured permission to undertake1 at the navy yard1 some experiments concerning the carrying capacity of a magnet at varying distances between the pole and the armature1 and at the same time he sketched out the construction of an electro-motor1 especially well adapted to utilize the magnetic attraction4 ,this electro-motor was built in ,copenhagen with funds granted by the ,classenske ,fideicommis4 ,when it was finished1 ,hjorth applied for the money needed to make it double acting4 ,in autumn #ahfj1 ,hjorth was in ,paris1 and there he worked for his electrical inventions4 ,in #ahff1 ,wilde published his machine1 in which the current needed to magnetize the electro-magnets was produced by a permanent magnet4 ,this is exactly the principle1 underlying the dynamos built by ,hjorth in #ahed and #ahee4 ,hjorth's good friend1 ,wm4 ,macredie1 ,melbourne1 sent ,hjorth a clipping from an ,english periodical mentioning ,wilde's machine1 and called his attention to the identity4 ,it is to be regretted that ,hjorth's answer is not known1 as his copy-book for #ahff has been lost4 ,considering the data at hand when ,hjorth's biography was published in #aijg1 one might be inclined to believe that ,hjorth had invented the dynamo principle and then dropped it at once1 going back to steel magnets4 ,it is1 however1 clearly evidenced1 by the papers left by ,hjorth1 that this has not been the case1 but that ,hjorth has used the dynamo principle1 in various1 more or less pure1 forms1 in practically all his projects from #ahea to #ahgj4 ,illustration3 ,fig4 #g4 ,sketch of ,hjorth's ,magneto-,electric ,machine #ahfg4 ,as previously mentioned1 ,hjorth had been disappointed in his attempts to produce energy through an electrical transmission of power1 but this did not cause him to relinquish the idea of producing energy by electric means4 ,he took this up again in a new form in his old age4 ,in order to have this idea carried out in practice1 ,hjorth had a machine built1 a description and drawing of which is to be found in a pamphlet published later on in ,french and ,danish4 ,from this it appears that the machine was not originally built according to the dynamo principle4 ,hjorth found no advantage in using the expensive electro-magnets1 as it was his main object to prove that1 by his special arrangement of armatures and magnets1 he could reduce the power required to produce a certain amount of electrical energy4 ,the machine1 in its manner of construction1 reminds one to some extent1 of ,hjorth's project of #ahea4 ,two or three rings1 or wheels1 of armature coils ,a 7see ,fig4 #g7 revolve between three or four circular rows of magnets ,m4 ,this decreased consumption of power was to be attained by offsetting the armature wheels somewhat relatively to one another1 for instance so that when one armature of the topmost wheel was opposite one magnet pole1 an armature of the next armature wheel would be spaced one quarter of a pole distance from a pole1 and an armature of the lowest wheel would be one half pole distance from a pole4 ,as it is well known1 this idea is entirely erroneous1 it being contrary to the axiom of the constancy of energy4 ,the machine was built into a casing1 and was sent to the ,paris exhibition of #ahfg4 ,hjorth was always very careful not to give any information about his inventions to anybody4 ,at the end of ,april1 he went to ,paris himself4 ,the machine had suffered some injury on the journey1 and had to be repaired in ,paris1 and therefore it made its appearance rather late4 ,still he succeeded in having it submitted to the judgment of the jury1 and a test of electrolytic deposition was made1 which proved entirely successful4 ,in ,paris he met a certain business-man who1 later on1 requested to enter into partnership with ,hjorth4 ,this man was an adventurer1 whose ambition was to become a ,knight of ,danebrog4 ,it is only to be regretted that this person obtained so great a power over ,hjorth1 and understood how to deceive him4 ,the previously mentioned pamphlet1 edited by the partner1 and named ,batterie magnto-lectrique de ,sren ,hjorth1 is a document of the poorest kind4 ,through his partner1 ,hjorth was introduced to various electricians and men of science1 among others the renowned ,samuel ,b4 ,morse1 who recommended ,hjorth's machine1 but took exception to his idea concerning the production of energy4 ,the electrician who repaired ,hjorth's machine1 introduced him to the president of the ,french ,socit d',encouragement1 who had proposed a competition for electrical machines1 and had offered a prize of #cjjj fr4 for a machine1 complying with the conditions given4 ,hjorth's machine was sent to the society1 but he did not succeed in obtaining the prize1 which was awarded to the subsequently so famous ,alliance machine4 ,on the #gth of ,july1 ,hjorth1 probably prompted by his partner1 obtained an audience of ,emperor ,napoleon ,,iii4 ,after he had demonstrated his invention1 and shown the letter from ,professor ,morse1 the ,emperor asked him what he could do for him1 and ,hjorth answered that his highest desire was to have a larger machine built1 and he requested the ,emperor's protection and assistance1 in order to accomplish this4 ,the ,emperor ordered an examination of the machine to be made4 ,the well-known ,professor ,jamin was retained as an expert1 and ,hjorth demonstrated the machine before him4 ,on the following day it was examined1 in the presence of ,hjorth and his partner1 by ,jamin and other men of science4 ,they subsequently had the machine sent to the exposition1 where they measured the voltage and intensity of current1 and expressed their satisfaction1 as to the results attained4 ,nevertheless ,hjorth was disappointed to receive1 the next day1 through the representative of the ,emperor1 ,general ,fav1 a communication that the subvention applied for could not be granted4 ,at the exposition1 a great sensation was created by a dynamo exhibited by ,ladd4 ,this machine had two electro-magnets and two armatures1 the current being directed from the smaller armature round the electro-magnets and taken from the larger armature to the exterior circuit1 lights for instance4 ,thus the machine was evidently built according to the dynamo principle4 ,in order to claim his right of priority to this principle1 ,hjorth went to the prominent authority on physics1 ,count ,th4 du ,moncel1 who later on became the editor of ,la lumire lectrique4 ,as ,hjorth himself did not know ,french1 the interview probably took place through his partner4 ,about this1 ,moncel writes in the above mentioned periodical1 in #ahhc1 that ,hjorth's representative was not very conversant with electrical matters2 therefore he was unable to express himself clearly1 and consequently ,hjorth's rights of priority were not acknowledged4 ,having received the ,emperor's refusal1 ,hjorth went home1 broken down by illness and disappointments4 ,in #ahfh-fi ,hjorth1 due to the interest taken in his case by the manufacturer ,mr4 ,khler1 succeeded in having a small machine built in this gentleman's shop in ,korsr4 ,at the same time1 a larger machine was made in ,copenhagen1 the necessary funds being contributed by several country gentlemen and merchants interested in the case4 ,finally1 in ,december1 #ahfh1 a body of prominent men addressed the government1 petitioning a subvention of #ae1jjj rixdollars to be given to ,hjorth1 in order to enable him to build a new and larger machine4 ,as the ,ministry was not inclined to grant a sum of this size1 it proposed to grant #ajjj rixdollars1 in order to have the existing machines examined by ,professor ,hummel and other experts4 ,this proposition was accepted by ,hjorth1 and a commission was formed1 consisting of ,professor ,hummel1 assisted by ,professor ,holten1 ,instructor ,lorenz and ,winstrup1 a mechanic4 ,as early as ,december1 #ahfh1 ,professor ,hummel1 together with head-master ,ibsen from ,sor1 had visited dyer ,glich of ,christianshavn1 where one of the machines was located1 and they made a few tests1 which ,hummel himself did not consider to be of any importance4 ,the experiments were to be made in ,april1 #ahfi1 after an assistant had made a preliminary experiment1 but then ,khler reported that he had taken the machine apart1 in order to make an alteration therein1 and that this would take a couple of months4 ,it appears1 from a letter from ,hjorth to the ,ministry of the ,interior1 that ,hjorth had arrived at the conclusion that he must resort to the use of electro-magnets1 to a certain extent1 at least1 on account of the steel1 by continued use1 losing part of its magnetic power1 which necessitates its being re-magnetized1 and partly because it appears that electro-magnets may be made to yield a considerably larger magnetic power than steel magnets1 by means of the electrical current induced thereby4 ,as this change to the dynamo principle was estimated to cost #djj rixdollars1 ,hjorth was informed1 in ,april #ahfi1 that this amount would be paid out of the sum1 granted for the experiments1 when the smaller machine had been re-built4 ,hjorth's answer to this was a petition that the #djj rixdollars might be spent on any battery1 which he might build4 ,hereafter the case died out4 ,his petition was not answered until in ,april #ahgj1 and the answer was a refusal4--,at that time ,hjorth was in delicate health1 and his energy had been broken1 and a few month's afterwards he died1 on the #bhth of ,august1 #ahgj4 ,he was survived by his wife1 who died on the #cjth of ,september #ahhe4 ,this indefatigable worker did not succeed in seeing or reaping the harvest of his work for the utilization of electricity1--perhaps his aim had been too high4 ,at a period when in all countries stone was added to stone in the foundation now supporting electrical engineering1 we ,danes have also made our contribution4 ,hjorth did not possess the profound knowledge nor the sharper insight necessary in order to avoid errors1 but his perseverance1 his industry1 and his sacrifices1 ought to be acknowledged1 and his name ought to be venerated on account of his contributions to the development of electric machinery4 ,,footnote3 #i ,hjorth's ,english passport1 from #ahee1 contains this information3 ,height3 #e feet #g inches1 ,complexion3 fresh1 ,eyes and ,hair3 grey4 ,,sources4 ,after ,hjorth's death1 few knew that he had discovered the dynamo principle4 ,if ,hjorth himself had understood the importance of this discovery1 and the magnitude of the revolutions to be caused thereby1 he would undoubtedly have endeavoured to propagate the knowledge thereof4 ,it was not until #ahgi1 when ,colonel ,bolton read a paper before the ,society of ,telegraph ,engineers in ,london1 that ,hjorth's patent ,no4 #baih1 of #ahed1 was again brought out of oblivion1 and accompanied by these words3 ,this appears to involve the principle which was later on taken up by others4 ,count du ,moncel1 who had received ,hjorth's representative in #ahfg1 when reading these words1 was reminded of the case4 ,thereafter he has given ,hjorth a fair redress in the above-cited article in the valuable periodical ,la lumire lectrique1 edited by him1 the heading being ,the ,actual ,inventor of the ,principle of the ,dynamo-,electric ,machine4 ,among the few printed sources of information concerning ,sren ,hjorth and his inventions1 the following may also be mentioned3 ,c4 ,nyrop3 ,industriforeningen i ,kbenhavn1 #ahch-ahhh4 ,du ,moncel3 ,l'clairage lectrique1 #ahhd1 page #ajb4 ,electrician1 ,july #hth1 #ahhb4 ,la lumire lectrique1 #ahhc1 ,,viii1 page #eh4 ,the most important source is the papers1 left by ,hjorth1 which comprise a considerable collection of drawings1 letters1 and rough copies of letters written by him4 ,these documents furnish full information1 not only of ,hjorth's inventions1 but also of his entire reasoning and manner of being4 ,probably the most interesting of all are his note-books and sketch-books1 wherein he used to note down his ideas in ,english1 and which are accompanied by neatly made1 coloured sketches4 ,these papers were not accessible to the public until the autumn of #aijh1 and they are now preserved in the archives and library of the ,polytechnic ,institute in ,copenhagen4 ,important contributions to ,hjorth's history have also been obtained from the ,state ,archives1 the ,archives of the ,society of ,science1 the ,archives of the ,polytechnic ,institute and from the papers left by ,h4 ,c4 rsted4 99 99 99 99 99 ,transcriber's ,notes3 ,footnotes have been moved to the end of each chapter and relabeled consecutively through the document4 ,illustrations have been moved to paragraph breaks near where they are mentioned4 ,punctuation has been made consistent4 ,variations in spelling and hyphenation were retained as they appear in the original publication1 except that obvious typographical errors have been corrected4