Zur Anseinandcrsetzun!!; zwit;chen der Weberschen Theorie del" Elektrizitat
lind der emfkommenden lVIaxwelIschen Elektrodynaillik
Andf(~ Koch Torres Assis, Campinas, Sao Paulo, Brasil, and Karl Heinrich \Vicdcrkehr, Hamburg
Zusamrnenfassung Die Abhandlllllg spt7:t sidl mit del' Ablos\lll!-\ der iilterPIl Ekktrodynamik vou \Vilhdill \Ve bef und Fran;. Npumunll durch die .\laxwf'lJschr Theoric im lebten Drittel des 19. .lahr h\llldf'rt~ aus!'inClIHirr. AuflliingrT fiir die Darst.ellllng der Pl'oblcl11 Abstract This a.rticle deah-; with the super~("Hsiun of \Vilhelm \Veher's and FraIl;" NeUlllann's 01- dpr tlwory of electrodynamics by :\IaxwcJr~ theory in the last Lhinl of thc 19th cenlury. St,arting-poini; and l)<-l~is for the present.ation arc th(" few quotatiolls Lhat. Gill be found ill \\-'el)('r's work~. The discu~Hi()1I was mainly p(~rforilled by C 53 1 Introduction Two of thc~ leading figure~ of XTXth century elenrodynamk~ were James Clerk II;Iaxwl'll (18.31 1870) and \Vilhelm Eduard \Yelwr (1804 1891), 27 ye;(trs oldc'r than \laxwC'i1 ([OJ a portrait of \Yilhelm \Y,o'iwr see pal',e 8). It ic. well kllown ,hat :\1axwell quot(;d in hi~ papers on e[e~Lromagndislll of 18~3, 1864 amI 1868 the wOiks of \Veber, sl'e [II, 121. I:~] and [-'1]. In Maxwell's "Jfreatisc on Electricity and Magnetism (1873), which illtwclm·{"cl to Continental Europe a new epoch of resC'areh into electricity, \Vilhdm \V<:'1)('r. !Hext ro i\.lidlael Faraday and VViliiam Thomson (Lord KelYin), is most fn"(juPIltly (l1lOt('ti, 15]. \Vhat if, airnofot unknown is that \V",iwr also quoted }laxwell a few times in his works. \Vilhelm \Ye!JPr had alrpady formulated a fullfiedl',ed theory of p[edr()(lynamics, which was acknowledged on the Conlinenl unlil lhe 1870's as one of the leading ones. logether with th(" studi("s of Fnm7. SeumanIl. It dealt with t.hp alr('atiy \wll-knO"wn pIWll()]ll('lla of mag-ndisHl ami diamapldi~IlI using a~ support the hypothp~es of (;It'ct.rical lllol('cular currents, Coulomb's law of plectrostaticC', Ampere's study of attraction 2 First and Second Quotations The fir~t quotation appears in a paper of 1871: "Electrodyna.mic Illea~menwllt~ relat.ing ~lH' cially to ,ht; principle of the conseryation ofenprgy", [7, Vol. 4, pp. 247 299. H(~(, esp. p. 2GIJ. This pappr has already been translated into Engli~h, [B, see esp. p. nl. It is only all imli teet citation, as he i~ quoting Tait's work and it i~ Tait that. cites \"] In Profl'ssor Taies very instructive work, 'A Sketch of TIH'IIllOd:dtalllics· (EdinbUIgh, 1868), the following passage occurs al page 76, ill referenc(' ~o the investigations of Riemann and LOr 51 Clos(·l,. rekvant i~ tilt' f>econd quotation, which appear!; in a paper of 1878, the "eventh papl'r in thp fatuous ~l'rie;; of Elfxtr-odynamic Measll,n:mnifs, ]91, 5cr r:~p, p. 36;{ of Vol. ,j of \V('l)('r'~ vVf,r·h:. Thi;; quot(ltion deals with the ~(lllH~ t.opic and appcar;; in the first paragraph of t,hi~ papr'r, our ~ran;;latioll: l1('lmholt7. lIIailltain(~d, and \ViIliam Thom~Oll, Tait and others agn~pd with him, that the general fundamental law of electrical adion pr('~ented ill the ~'ear 18'lG in thE:' Electrodynamic J\:le(ll'nrements1, to which waH added in Pog geIl(!orlI's Ann,llen 1848, VoL 73, p. 229,2 the dcriY{~d potential of the dcct.ric fOIl'e, wa~ in contradiction with principle of thc con~('rvatioll of energy; ho w('y('r C. Neuman)] and }Iaxwell demon~tra.tf~d the opposi~(', proving thar all ,'lTOl' Wfts madl~ in the prE'SPllLation of the theorem by Helmholtz, that the prill('ipil" of the cons('rv(ltion of energy i~ valid only for [or("l~s which dE'pE'nd 801d:1f on tlj(~ distanc<' ..'l The ~t(lrt of til(> con[.rovers.y bd,ween \Vilhclm \Vpher and Hermann von HelIflholt~ (1821- 18(4) dates back LO 1847. In hi~ fatuous your-Mill study On the ronseTl}ation of force H('llllholtz m1un(.aiJl('d, when considering cr:ntr(ll forces, t.ha~ the law propounded by \Ve ber was at variance with ~he principle of the con5crv'l.tioll of energy. Illl, with English t.ran~lation in [12J. The rrH.<;on W(lH that in \Veber\ force, heyond t.hc 1/r2 Conlombiall tCllll_ t,jH'l"(' wpr<' t,erillS dependin~ on tllE' relative velocit.y amI acceleration lw,tween the intt'ract.ing electrical charge;; (or rather cledrical particie;,)4. \'Veber had ~pecified in 18,'18 a t("rm for the pot(~nti(ll of eledrical encrg:v, [16J, with English translation in llOl-" Herma.ml von Helmholtz continned to at-g-ue ahout thiH problem in spvera.l treatises [rom 1870-187.';i, trying Lo e~tahlish a distinction between the hitherto concurring eledrical theorie~, ("s,,<;ellti ally t)]O;;(~ of\Veber and :\Iaxwdl, [17, sep esp. pp_ 345, 636 aIUI647] atld 118, pp. 8748891_ Helmholtz tried to prove that two electrical p(lrticies, moving accoTding to \Veber's law, CaJI attain an infinitely high speed, which wonld contradict t.he principlE' of energy conser vat.ioll. Thl' ~o-c(llled "crit.ical dis~Hllce" (\Vpber's "mole('ular ~ize, or dimension") play~ the deciHiw role in thi~ matter. \Veber dr:fended his position wit.h hiH ~tlldy of 1871, 1191 with E))glish fr(lI1Hiatioll in 181- J'l'tr'r Gnthrie Tai~ now embraced iII his "Sketch of Thermodynamic~" (1868) thp alrca d,Y obsol('w point of view of Helrnholt~ of 18'17, [20J. Abo ill the work "TreatiHe un :'\aturru l'itiloHophy" (l867) by \'V. ThoIllson and P. G. T(lit this criticism of \Veber'H law was re peated, ]21], H. Helrnholt~ and G_ 'vV("rt.heim were responsihle for the German tr(ln~lat.ioll publi~hed in two parts (1871 and 1874), [22J and 123]. \Yeber'H law was ciesrribpd here as illter{'~li)lg IS,'" public-alion for tl,,' e~1 ablishmenc of' tlw Royal Saxonian Society of Seirncc. Leipzig 18,16. I\Vilbdm \Vpber'~ \\'(>rk,\ Vol. HI, p. :25. [7. Vol. .1, pp. 25-2141_1 21\\,ill1('hn \\""I)(,,-'~ \Verkc, Vol. ITT, p. 2'L~, [7, Vol. 3. pp_ 215-2"d. ~ee esp. p. 2451 with B"g,li~b transial.iolL ill 110, soe ~~p~("ially p. 5201.] :lSee al~o Ad. ]1.. Tny,'[: "Urher den allge",eiJl~ten Ausdru("k der in""ren POlentialkrafte eille~ Sy~1.(}ms bpWe!W'T malrrieller Punkle, w~lches sich all~ dem PriTicip der Glcichheit von \Virkllng und CpW'JI1NiIiulllg ('rgiebt" ll.-Iathrmat.ische Annalen, Vol. 13, p. 20 . .1\.vd)rr'~ for('e acting b~1.wpe" liJC electrical charg",~ C fl.ml e' 5Pparated b," a diAI,aIlce or is along the ~traiglol. linr. connecting them and is given by (ee ' /or 2 )(1 r2/':~I' + 2rf/C";;l'l_ Hprl''''' -= dr/dt, j' = d~'I"/dl.~ and elY is \Veber'A coIlsl.ant. In 1855-1856 \Vl'ber and Kohlrau~("h [OllIld rxpcrimentally itb w),lm:. "1'1' = 4.:394.:'0 x IOlJ rn.m/8, chat i~, e%eniinlly h Urnes the light ve1oril.y in air, [BJ, IHI aad IVil· ~\V~lwr's P()I.'~I1l.iitl energy j~ given by (eel/r)(l - f2/cfv l. (1831 1882), saw t,hest' da.im.~ &'; frivolous and irrespOlIsihl('. In lilt' introductioll to jlis hook "Oil the l\at,lIre of COIiH~t.S- (Leip;>;ig 1872). p·l], he r('proadlCd Helmholtz for !lot havi!lg Lakf'n ('Hough Cill·,' to rt' After hi~ hook Oil cOlllets, ZiiliTwr wrote ~('"pral more art,klf'~ in d{'('(·ll{'(' of \VPiwr·s viewpoints, inh'ndiIlg abo to !"('ply ill part to attadcli llladt' upon hillliit'lf. Tllf' t.oue i)('nlll)(, ~ha.rJlt'r and more polemic, awl t.ook on. 11I01'POVt'1'. a Ilatiollalilitie flavour, Th('s(' W('H' til{' .\'f·ars aft.cr t.ht' frau("o-Prussiau \Var, aud r ht' COlluding of t.he (:f'rIlH\n fit'it'h h~' Bi~liIar("k. ZiilhH'r WlIS a ~llpport,er 01· spiri LualislIl, which CHIne froIn England (s(';-Illc{'s with a 1l1(' ;:;6 Fig. 1: Johann Karl Fri0drich ZiillIlt'f (184:3·-IRS2) lklll.~cll('," Idll~"llm l\iiinc1",,,. IJl\ :i.")07"i' 57 wrote letterH in French. Letters by him in £.ngli~h are not knowIl to Ub. He IIlU~t however had a cert.ain knowledge of English, for in 1838 he went. on a fairly long jOUrTlC'y t.hrough England, and met a number of scientists. In his article, Zollner reproduced ]V[axwcll's Illork largerly in German. In order to defend his theory of act.ion by contact (field thc'ory), \bx well offered in hiH addresH the thesi~ That I\"ewton, while desr:ribing i,>TavitatioIl a.<; ~ubj",ct to Ziillncr also cited Imm(l.nuel Kant (II-; chief wit.neH~. The problplll ih ht.ill being dis("1lsHed today in the literature of hisTorical physicH. For Ziillner the views of I\Iaxweli and also \\-'. Thomson represenL a stcp-back of more Lhan LwO ccnLnries, which carns Lhem lhe 11iciOlame of "modcrn Cartesians". For J\.1mcwell. Faraday is t.he initiator of a concept of continuum. Zollner, in conLras(., seeks to claim that Faraday stood for an atomistic con("C~pt of electricity. In our opinion, ,md indeed that of mo~t hi~torian~ of physicH, Farad(l.")' rpjecU~d the pxiht.ence of a snhst.ant.ial electrical charw~, and abo the exiHt.ence of atom~ and moleculps wit.h maSH. For him thprp were only force-field~, possibly bound to insub"tantial nudei, ]351. ]I;[axwell also writes in his Treatise on the subjc~ct of ekctroi~'sis: ''The electrificat.ion of a molenlle, howP\"l'r, though casily spoken of, is not so e(lsily conceived", [5, ~260, p. 3801. Thl' (Tucial point of \'Ileber's con("C~pt i~, in contra5t, the genuinc~ exi~tence of t.wo kinds of dect.rical atOltlH, Oil(' positiye charge aud the other negatiye chal"g'e. His cOIlcept was later OIl confirmed by H ..\. LorenL",'s Lheory of electrons. \Vhen :vlaxwell began his study of electrical phenomena, he at first imIllerHell hilll~(·lf compidrly in Faraday's rea~onings. Finall.v, however, when writing his tn'at.i~e "On phYHiral lines of forc(," (1861), [2], he occupied him~elf more inten~ively wit.h \Vdwr's ·writings. Hr' adopted the result of a nH'aSUTemc~nt. of the relation~hip between the ahsoluw elect.ro~t'l.tic and the absolute electromagnetic charge, a.''; determined by R.wlolf Kohlransch and \Vilhelm \Veber. This was in fact the speed of light. and it was one of Lhe main poinLs helping Lowards the creation of the theory of the eledromagneLic nat.ure of lighL (186·1). PJ and ]36]. In Lhe introdudion LO his LreaLise "1\ d:v"namical Lheory of Lhe eledronwgnetic field", at t.he end of which he develops his electrodynamic t.heory of light., and aiHo conHidpr~ the (iu hiH opinion) <:l.dmirable writing~ of \Vilhelm \Veber, he ouly dpdinp~ to That. HelmholtL;, \Villiam Thomson and TaiL Ivere wrong in supposing LhaL \Vebel'~ force was incompatible with the con~eryation of l'nl'rg~' wa~ ~hown not only by \Veller in hi~ paper of 1871, but alM) by :Vlaxwell himself in the iaHt chapter of the TY'HLt-IHI:, 1'), Vol. 2, Chapt. 23], [38, Chapt. 3J and [39, Chapt. llJ. Helmholt~ in 1847 had consid(>rrd ('('nllal forces whirh depend on position ami velocity, showing that th<'y were incompa.tibk wilh the principle of the conseryation of energy. \VebE'r's force la.w, on Lhe oLher han,d, lkpelld~ not only on the dist(lnce between th(" chargeH 58 3 Third and Fifth Quotations Til(' sa1tl(' subjcct-areas arc tf(-~ated in the t,hin! (two cit.ations in tllf~ same page') ami fifLh quotatioIls, so that thcy ~hould bc di~cllssed t,ogdhel'. The third quotation comes from hi~ work of 1878, [9] and e~p. p. 395 of Vul. ,1 of Wplwr's Werke. III Scct.ion 8 of thi~ pappr Vi/cber i~ discu~~ing- t.he applicatioll to luminiferous ether all(\ to ga~ps of the theory of rcA('xion and ~c(!t.tel'illg of d("ctric raYH an:oniing t.o his theory ,md also thc works of Kr6nig- ,llld ClaU~i\lH, A dis("u~~ion of the wOl'ks of Krollig and Cl"u~ius Gill be found in I-m, Vol. 1 pp. 193-81, while eomn1(-"nts about \Vebel"s di~russioll auout n~fiexion and scattering of particles can IlP found in ]40, Vol. 2, pp. 77- 791. The third qllotation runH as follow~, our tnlJlslation: If iH posO'ible to Lran.';cribe thc hWOi found in tllP pl'eYiou~ Section [or t,hp l'efie- xion and ~t;H,teriIlg of rays compo~(.'d of eiE'dric particlE's of thp same kind abo to rayH of pondel'abl(' IlIo]ccules. according to :\Io~ot,ti'~ ClHlcepUon ("OIllposed Tllol('cules. And when thps(' pondcrablp Illoleeulp~ are now g;J~ molecules, then a state of aggregation of t.hp gas wiU be built by thi~ means, which corrcsponds pntir(>ly to t.hp stale of ap,grE'gaLion according to Krijnig-Clall~ius's l,bcory of gascs, witilOul heing neecs:-;ary to ascribe to thE'se pondel'able molecules a special f(ll"Ill and el Thes(' lllolpcular di~t,allce~ for pou 59 question In the treati~e of the third quotation \:Vilhdm \Vebel· look issup with [("newed obj('rtioll~ by Helmholtz to his basic law of electricity, dra,Ying support ±i-om arguments exprp~~cd by Carl :'-l'eumaiin. In addition to o~hcr matter~, \Vp!wr w p=2 -+-1 j ) ( E 0;/ Gl\Vilhelm \'\Ieber's Werke, Vol. IV, p. ;31:\91. [7, \'01. 4, pp. :\61-4J2, Ree "~p. Pl'. :):-l!) :)~Hl- GO / .I Fi~_ 2: Carl NC'UIn;uul ("LS:32 102,)) 61 Iklll~d]('~ \lllH'II111 \lii"d,,'jJ, UN 1.-17,~<-)_ In this, rand (" arc Lhe charges, 0; and c' tlw associaLed inE'rtial lIIa.<;HeH awl ('w the \Veher conHtallt. Th(" ahsolutc value of p is very sm 62 hmall-~i/ed ('rl1('r pal'tides rotat.ed, \\-'. C. Ilankd wanted to Lransfer tllt~ plectrical pheno mena t.o the ether. ,md Erik Edlund dPyploped in 1872 an ptht'T theory of dpctricity. In COlltra~t. to ill! this, \Yilhf'hn \!I,leber stood firm on lhe acceptance of Lwo kindh of electrical ('ntiti("~ with atomic HtrnctUfe, and (Ill chemical atom~ and moleeules wen" to be based on t.ht'~(, (for rderenceh about t.IH" ether theor.v of (,!('ctricity, see 118, p. 921]). J. K_ F_ Ziillner had sLakp. -12·1 and 429], 140J and [47]. \Vilhclm \Veeber r",fer 00 thiH in the third quot(l,tion WP had comm("nted OIl, Whe)l dealing with t.he f(Jl"(:es of repuiHion bet,wcen ga~ particles. These forceH arisp when t,he (nellual) ga~ panide~ iJl th("ir projel'lile motion draw ncar to molecular diskulCes_ ZiilhH'r cOilHide("ed two Hilllple ponderable IIlolecules which an" formed from thp hasic ('lpctri("al pankkH, rphlH'ctivcly +('1 (l,nd -ej. and +('2 and -f:~. Aceording to Coulumb's law, Ihcre are rhe l''''pltlsive forc,,~ (+f'l)(+C~) and (-el)(-e2). and thp fOl'ces of a~~ritction (+f'J)(-r2) and (-f'1)(+('2) Previously iL lJad bepn accepted that tlH~ repul~ive force IWt'\-vc'l'll t.wo equal basic particips is equal to the forcp of al~ranion l)etwpen oppositdy eharg(-'(l ba.~ie parUcks. Ziillner now maint(lined that lhere was a tiny diiTen'l1C(' hetwePII tlu'H(' forcp~: lhe forC(" of attraction was ver.Y hlightly greater than thp force of H"puiHion. The diff"t>rcllce b HO kmall that il cannor IH' detected experimentally. In ~hi~ diff'erencf', however, Ziillner saw t.hp SOlll'Ce of gravitation between the two pOllderablc' panicles. Cravitation, tlif'n, is a n'~ultant. a residue of electrostalic for('Ps. AH the basic d("ctri(:al pa.rticles also p(lSH("~H a mechanically inprtia.1 mass, this rehidual force is also propurtional to th" product of thp lllasse~, and illver~ely proportioIl 63 pondcrable mulf'cule"" that. i~, t.he sum of twu aTtr<-l(:Tion~ and l,\iO wpuiHion~ hetwp(~n lhe dlargek +(' and -e of one molecule, and t.he charges +e and _(0 of t.hc other IlJoh"cnle. The net re~l.1lt (assuming his fimdarnent.alla.w t.o be at work here) ie; given by, ]48, p. 48:11: -20'--;;-" ( 1- -,-I (eJ")"- + -,---,2,· d'c) r- cIV dt elY dt Thi~ would be the equivalent to a gravitational attractioll bClwccn the nlOle("uleH, derived only frum cicelromagnetic f(Jr(:('~. \.\'hcl\ Llw powlf'rable parridp~ come into \'ery close proximiTy, repllbi\"c forces arise, which carl be formally estimated in a.ccordancc with the laws a.irf'ady developed for (,he two ba..,;ic partich.. ~, [7, Vol. '1, pp. :385 and 3891, giving t.he ree;uliant. valuf' p for the molecular siLeo The forrnul {i4 t ig. 3: .lallH'S Clc'rk J\TaxwdJ (lR:H 1879) ('alllplwll, I. ~JLd \'V (;,mwH: Thl' I.ir(' or .Le1. :-'!a...<:well wil"il ~d\'Cl.iOIl~ [rom hi~ ('orr('~puTl(k"rr and ()end,iomol WliliTll',s. :-lpw editioll. l.()"dn" ISPA, 65 number'll there will be several po~~ib1c ways of constructing a ponder [ ~: 1 [~; 1 [~: 1 [~11 for greater Il let us seled just one of the many po~~ibilit.ie~, namel:-" with Lite 'Ii positive unitips togdher and n s8paratE' negatiye unities: -i-Il -1 -1 Here one is reminded of the atomic model of Bohr and Soullllt'rfeld, If we ,lH(Tilw a very large inerUal mass to a positive" ha..,ic p 4 Fourth Quotation The fourth quotation appear~ in a joint paper by \V. \Veher and F Zollner, 17, Vol. /1. pp. 420 476]. It wa~ published in 1880 and is the la~t pappr publi~lwd by \\-'eber during hiH life. The motivarion to cooperar.e was lo establish a practical value for t1w ab~olute unit of re~i~t.an('e, the Ohm. Tllt'y distusH rhe ahsolnte ~y~r,em for magnetic- and ('lectroma.gnetic unitip.~ int.roduced by Gauss and \Veber, concentrilting on the absolu~e unit for elN·trical resi~tance. \Veber had presented four different practical methods for reducing the unit of rt'sistance to <:tL~oJutc~ measures. Due to the pnu:tic AbouL UlC mcmber~ of the Committee reported the Repo'rt, p. Ill, literally: "Thp ComIllitt(~e con~i~ts of - Professor \Vhearstoue, Prof(·~sor \Villialll~on, l\lr. C. F. Varley, Professor Thomson, Mr. Balf(mr Sklvart, I\-fr. C. W. Siem811s, Dr. A. :\fatthipssen, Professor 11axwdl, Professor Miller, Dr. .}ouh·, J\.lr. Fleeming Jenkin, Dr. EsselLach, Sir C. Bright." A general discussion of tIlt' formatioIl ilud re~ult~ obtained by lhis COIllIllitt(' Ull plectrical ~tandard~ can be found in ]50, pp. 687 698]. Some information about. I·he IIleml)(>r~ of thi~ Committee: Charles \Vheatston(' (liW2 1875), for il, short time profC'ssor of (·X'[WrilIH'ntal physics at King'H College" in LondOll, was a distinguished invemor of apparatus ,mo nW,,$lJ ring ins~ruments for U{~tollsticH, optic~ and electrichy_ He constructed ~eyt'ral inHtrumentH 66 for tdl'gr of ot.her phy~icists to crcate' (I f'r,andar-d for H,,,istarlce. \Vith t.h(" installaUon of t.elE'graphic condu("fors ami submarine cables arose ;lIl urgent necessiTy to create 67 Fig. ,1: William Th()lII~(lil (Lord Kl,h'in) (l80-l 19(1) TI,()ml'~'"'' :-;ilv".",,~: ·I·h,· I.il",· "I \Villiil,lrL l'hoJJl",''', 11,1)0[[ I("]"il] of 1.,tI).',N. :] \'ob. 1.olHioll i!IIO. \'01. 1, 1', ,"):\,"), of \Vilhdm \V(,ber'H, Wllich Thomsoll improY('("i. Thi~ method, or pro('etlurC', \ The llndertaking of [.lw British A~~ociation to (Teate definilion~ for the i\-J()fit~ Hermann von .hwobi (1801 1874), who developed (>lectro~'yping - he was bro tlwr t.o a well-knO'wII Ilw(.])('mat.ician. K,u'l Gust Ullfort.unatel~' iL enWfgt"d that in ~hc' pl,u:e chosen for setting up thE' l\\'O mils (at. t.he 1'1('iskenbnrg in i.-eip7.ig), the tempPfaturp did not. remain HufficiE'ntly constaIlt, Thus tlw pn~ci~(' IIl"a~uring th'lt W Th(' (Tf'ation of a more eXi\('t yaiue for ~tandarcl resi~t<:lnre held thl' att.ention or nu llWf()llS ph}'sids~~ from various countri("s, eyen anc)' thl' P Acknowledgments: OIl(-~ of tIle authun, (AKTA) \\iishes to thank the Alexander von Humboldt Foullriation or Gprmany for a resemch fellov.rship during whid, this work wa~ accomplished. The a.uth()r~ thank Dr.B. Golyba.'ih for calling their at.tention to the third quotation discussed IIPre. Literatur [lJ lvfa.;l(welL J. C.: On Faraday's lines of forcc. In: NiVPlI, \V D. (ed.): The Sr:irmt~(ie Papers oj Jam~s Dln'A- Maxwell, VoL 1. New York: Doyer 196,'), Jlal'p~ 1£;5-229. Artidp originally publishe(\ in 1855. [2J j\.Iaxwdl, J. C.: On phy~ical lines of force. 11): :,\iven, \\r.D. (ed.) The Scif:ntijic Papf:r"~ of James Clerk AIIl:cwell, Vol. 1. New -York: Dover 1965, pages 451-513. Article originally pnhlisllCd in 1861/62. [3j :\Iaxwell, J.e.: A dynaIIlital theory of the elenromagndic field. In: Siven, \V.D. (ed.): The SCIentific PI1Pf:T'!; of Jll1nes Cluk Afaxwcll, Vol. 1. l\ew '{orle Dover 1965, pages 526 597. Article originally published in 1864. [41 Agostino, S. d': A hsolute s?steIlls of l.HliLs and dilllen.~ioIlS of physital (lnantitie~: It link bdwecn \'Ileher\ electrodynamics and rvIaxwelL, t'lectromagnClic theor.Y of light. l'hysi~ 3:3 (1996), 5-51- [,')j l\Ta..':well, J. C.: A Trml'i~e on Bledricil:'-I and Magnetl,"1n. New York: DoV(~r 195·1- Original publication in 1873. [6J \Veber, \:V .. 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