Letter: Some Experiments In Tesla's Laboratory With Currents Of High Potential And High Frequency

Wednesday, March 29, 1899
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ELECTRICAL REVIEW AN ILLUSTRATED WEEKLY JOURNAL IOF SCIENTIFIC AND ELECTRICAL PROGRESS. - NEW YORK, WEDNESDAY, MARCH 29, 1899. '”‘°“‘"N”“' -1- ML Rlvntw PUBLISHING COIIPANY, Tllnel Building; 41 Park Row, New York. t SINGLE COPIES, I0 CENTS. En ered nt the Post Qmce, New York, BS Mall Matter of the Second Class. .ls ` 4 mv _ _. ._ _,._ J 1* JE’ _ J Y» ` , , ;,,,; fs... ,_ _ 1,_»_».,»r ` . _ _‘fi~»‘>§?"‘f =‘ - ` .si _~§[email protected] .f5 §»:_§~fi=" i 1' s. 50I'\E EXPERIMENTS IN TESLA'5 LABORATORY WITH CURRENTS OF HIGH POTENTIAL AND HICIH FREQUENCY. To we Enrron or Ewm-melt Review: Siucc the unfortunate accident of four years ago, which crippled und delayed my labors in ll number of lines so seriously, l have had but little time to devote to the fulfill- ment of a duty which, next to that of turning his best elforls to diligent inquiry in the fields he has chosen, is the most iinportnnt to it scientific man; namely, that of giving an exact record of the results ohlnined. l realize with sorrow every day thot, despite of all pains taken to this end, I nm gaining but very slowly on the material accumulated. Ideas come through I1 hiippy inspiration, appar- ently without much exertion, lint it is the working; out of the many lia|‘assirig=dcl:\ils und putting into it prescntuhle form which consumes time und i-uorgy. lt wus impossililc to nliamdon rcsenreli in new direc- tions, in which l have felt myself irre- sislihly |ll'l1\\`ll, and it wus equally ini- nossihle to do full justice to tho work partially completed, und I cun only hope to gradually retrieve my losses hy the only expedient zivailulsle, which is to redouble the zeel. It is not the nest plan to follow, Iconfcss, und is in radical opposition to ihe kindly advice given to nie hy ii great philoso- pher, but this nd mission umy serve to iefnte tho statements attributed to me to the elfect that I intended to live 200 yeurs hy sleeping most of the time! It may also show that it is not this mode of life which is respon- sible for the dchiy in the commer- cial introduction of my system of viuiunin tuhe ligliting, us has heen as- serted hy some people who huve found u. singular satisfaction in dwelling extensively in their columns on my proposed ghiss house on Long Island, which was to cover ueres of ground, und which was to be huilt for the purpose of vntcliing the sun’s rays; on my claims uf the discoveries

194: of ltoeutgen; on my invention on- nhling me to move and explode tor- pedo boats by will power, and on my ELECTRICAL REVIEW ahling scientific man to push investi- gation far out into these practically unknown regions? This Work was estimate how much science has been advanced by the beautiful instru- ments of measure which Lord Kelvin I ` “ ' ‘_ fé_\f?~.-1-";~1 W. "is W; se ‘W`5"`§3'i???"f5T‘!‘l " J fi” U " _` ___ -J "¢»__s_p;g-- n|~vp1~=_:e'_».,1I~5.a_; :nn ~1g-1~¢'f»:~-,Ls _ -g .»<~ »u‘¢= f, $;:.._rf§€;f~v ,a-ya., ~_ _.,6~»__ 1* " ‘Q ¢ ”[email protected]'¥'~--f%»~~>-¢»==s' 3\»I’sI§‘m;;e'»=',Q; "'§»..=r~.-it-1'-H ~:__f'*rv1."',L2=I"f¢ ‘ ~ _ r fx fi. :`= ' _ `f'12' - _;\~ .- --,T tmv';¢i-‘>§»f¢s‘;_g+.”Iafter# w e fr* _ wb _. 9; lips --»~» " “ ~- " ' 'ff_}£=".:`_l.€'F ~- ff. ~;"f&'»L5 “ 5 1r‘s.;a§*2~‘_iaM€¢Z\ »°f=“Efs?§i"Z€9 f il" 2- "~" as ' " -;f - : ‘T'i"l == ‘ \-_ -------“ V ' ' ' ~ _ _:meme-rr:--nm:m1_.__, ;3,;;y_~,;-1r»~1,;,}‘_'=,f g',=§;;;- ' :::.........._............. ~ ' ~ =; ;_ : -' »- :Qin ~ ;~=f1 ~ ' Q'sc1r¥-`¢»~® -1 -,st u »;-.lsym _‘M 1”-nr:-~ __ 1? _I-=_1Hf?»*‘ ° » J ~ » er-1 ~ 3:4 ‘ wwr-f.-=1»~___=<:;__=_v-~ ~ ;_ sa" "“~-i~ ‘f=°~"{@<,»i»;<_"f»¥[email protected],é'.-;: 4 _#ff "* .. _ _ _ _ I _. _ .~: gp _;_ __»a_:.,¢; =;=,_;»w¢<_» ,p - *sang af 5, _M ~ _ so-;!g;r<~_ i ~ ~. '¢<~;<» ns.. -“‘ - 'Ii'-5 sf' fr ig’:~1;sU's`Q"»~»w€£ ’="~‘ ff _ “sir H ' 75 ‘ ‘Q .3 _ '= ~ f 1 <=1»;:-»»,?g;:f&'i-.5-g.f.;2,§e2vfr§i=¢ » ` __='E¢_sZs¢_'_.f~~1_ '1‘lir%f£< - ,~ - _ -f_;t_3__~>»‘k,¢s¢ edu .wer .V Q is I _'_»-=-» M.-f :~ ~ ~ _ -_l'.~~ ' _ f Ti _ 2~'_~§`.~v:< ‘= Q' _naw _ _ ` I4 _.V _a_¢_.L_ &_~_,.:_;5)_,;.,¢te,,_v‘V_¢,:v,»*f_,snr ig; _ Ui *_ _ ,T _§§f_g;gQ,,;5`,,_»f_,y;_,:.:;:§q;_ _ - gtg, _ 4, '_ ~»<@,<_g,e,,5-_,>, ag? _ _ ' ‘ ‘_ if - .;frxf~~§f;<.<_ 3 . ,cg .°;~!s:f\=:-.;. ;¢.§,,-Fé"’-f§`;~`T'e;` i ‘Sw > '5' - '¢3.~'.if. ‘- » ..z.g,| _,trf;.;a;_1.;=.ss_.f1v»:».»,,z.__'f'&~ f*iiI,,=f»f`s _ _ ` .ii¢¢1=~H»”f16:`»_ ‘ »:"~1,:>_f9=1'ffl'<"=>:;<'1s.~”’_£ »?s~§vF* #; _ \,_,|L____L-‘r I-A -ML ,._?,;;,_'_-4:4=,'ilQ~;1’~*»~,§r$if»\“%y§»~=-y§’fw<'LI# 1.-_ a :I ~ _yy ;_;»,;~,x:»;~~;5,Q§,1»9,,¢~ ;L`g;,,grw»‘lt¢»;¢1;\_1g:.,¢-,pg 1- ' ~‘ ‘ v "`*i'1'>“i'~";>1~_f"5 _ _ _ _ i,\_.__-1.,:_=f-/<<_»av'_»; -_ ~» . Rr _ ~ fwéwdnts ° y __ _ _ _ .;_ _ __ __ _ fc, ,,,¢,,5§, C, _ _,Q , 5, I I f __ _, _ 5 »s;_.:__..__,_,,;,. , »_ _ __ _ _Y .;,___: ¢.»_____ __ -.»=»..f= ~~ _ g ‘ .~~»f _ .-$:5v‘~,a;»\i:ffQ? .i»`3 -cl"-\-le," yy* ~ , _ -w -~.\ ~ _I q£@¢r;4v;_ ,Awe I Wi" » _ ,,[email protected]_»-;;»t_ ~_ _ . * ’ . _. _,f '\" if 5* fr* gg _[_ __ ‘="i_m '_ I I -~ " _- _ ~__' 'rg -, ,:~ _ ~» _ _ ;_»~._» __ ___ . - __ ;» . I ~ _ ~~:..<+ of. Q , 4 ~ _ ¥--= =f¥~~=~' . 'l §mf~>-|-° _ V.. »‘ 'L-1 L""‘-"vp ., JN _. -_ *_ -av/'_ ~f_ ~ ~' -- ' _ pl: "WAI _ , M _[pl »_ _ ,gm , _ ,_- _i g -e`:?4§ V i753 ‘ “ __ 5 J' 1' if Q, ~ ` _: ~'\ ’ » , so ' ; g _i'__ ;.\,,»_w;‘_` __ ‘_ ‘_ ,__ _ ,L I __A = _ '~>'>_; _ s. --- ~» ~ _ -` vt _‘iii--- "§~ _¢ " - _-rf: t am* /man/svn FIN, ‘2.--" Hmm I€XI‘E\II>\I1lN'I'S IN '|IcsI.A`s I.\Ii

Marsh 29, 1899 ELECTRICAL REVIEW 195 forth carelessly such views and who, with but afewdays’, not to say hours’, experience with a device, venture be- fore scientific societies, apparently unmindful of the responsibility of such a step, and advance their im- perfect results and opinions hastily formed. The sparks may be long and brilliant, the display interesting to witness, and the audience, may be delighted, but one must doubt the value of such demonstrations. There is so little novelty in them, that one might easily perform a practical joke on the lecturer by describing in advance all his drawings, apparatus, experiments and theories, thus placing him in an awful predicament. Though such a course would be naturally im- polito, it might be found justified and excused by thc circumstances, for pre- mature expressions of opinion and dcinonsln'ations of this kind are re- sponsible for inuch evil, one of thcsc being the erroneous idea which they create in scientific circles as to the importance of an advance made. It grieves one to observe that, for ex- ample, such great work as that of Professor Dewar, which he turns out with clock regularity, is scarcely com- mented upon in the technical col- umns, whereas a worthless trap for in- terrupting currents,which usually con- sumes nine-tenths of the energy, and is, besides, useless for other reasons, and just suitable for the amusement of small boys, who are beginning their electrical experience with Leclanche batteries and $1.50 induction coils, is hailed as an important sciontilic dis- covery. An agreeable contrast is afforded by those few who patiently investigate, contented to lose thc credit for advances made rather than to present them to the world in an imperfect state, who form their opin- ions conscientiously, after a long and careful study, and have little to cor- rect afterward. The importance of the task of pro- viding proper implements for research in these various tields once recognized, it became the question in what line the efforts to>‘this end would be likely to be most profitable. A little thought showed that it was in investigating high electrical pressures, for these were needed in most instances. More than a passing thought was given to static electricity;with the experiments of Franklin as starting point. Various forms of generators of static electricity were experimented upon, and some new ones designed, to which l hopc to revert seine time, as they present some features of interest. The most valu- able outcome of these experiments was fi. method of conversion which I have described, and which enables the operation of any kind of devices of low tension from such a high-pressure source ,with perfect ease and safety, no niattor how high the tension. Soon, however, it wus recognized that with the above object in view generators of steady pressure were entirely impractical, quite apart from their incidental limitations. lt was exactly as if one attempted to drive piles into the ground by the application of continuous pressure. This would require ounuhersonie and powerful machinery, and would be very inconvenient. Aniincomparably better \vay of developing high pressure is by delivering violent blows as with a hanuner. ln such u case the motion of the linniincr being suddenly ur- rested pressure is developed on the point of impact, which is all the greater the smaller the displacement caused, and if there were lnaterial absolutely rigid, incompressible and inelastic, nn infinite pressure might thus be developed by a small blow. - L A "r ,,._,._.. . i 7 ‘f *- ‘B " ' ' i ,; 'Hg _ qs" '» . _ _ _rf ‘f ,- . , l if = ; , , , . ' ` _ ’ ;f , 7 r "" di - » v . I , i . - -- xl 1 _ ' _ ._ .1 ~ 1 - L ' f~ 5 , y V _ . . r , l 1 ~ l _ 5 ll ; E r | f' i ' ~ Q l _ a r ' - - T ~w-w 3 i ` 5333 - f.;,;"fx,¢,;i , __f ` .. if .=.~»ffrv-- »e=~ =, ~ Fm. 3.-“ some Exrsziirnniwrs IN TEFLAVS LABORATORY wrru cvimanrs or mon Poraivrrsr. AND mon FREQUENCY"~P|l0'I‘0GRAI’II snowmo A r=An'r on 'ma LABURATOIKY \\ =1°n A msconNnc'r ~ ' - ‘ EU REBONATING COIL EUPPDIITED UN AN INB¥ILA1ING STAND, AND ILLUMINATED BY THE BTREAIMIIQIKS PRODUCED, UTIIER. COILB REMAINING UNAFFECTED-'I‘IlE PRESSURE DEVELOPED IN TIIE REEONA’\"lN(i COIL IE OVER IIALF A MILLIQN VOLTS,

196 llenee one is forcibly driven to the use of a iransl`ormer or induction coil as means for producing' great electrical pressures. The first dillienlty en- countered was that o|` insulaliun, and it might be interesting and useful to show, chielly to those who are less familiar with this special subject, how by gradual improvement, from the ordinary ind|u:toriuin capable of furnishing currents of very moderate electro-niotive force, an apparatus was finally evolved in which there is practically no limit as to the pressure obtainable. Selecting iirst the closed core transformer, one easily recognizes that it is unsuitable for the attain- ment of the ohjeet in View for oli- vious reasons. Nevertheless. by adopt- ing the plan illustrated in the first diagram of Fig. 2. I snceeededxin oh- taining nearly 2<|l>,00l\ volts, and I think that more than twice this ten- sion is praeticable by means of such an arrangeuient, which involves the use of independent and entirely insulated ELECTRICAL REVIEW of the vlosed-<3ore type in the way of insulation, rule of change and fre- queiiey of the current impulses, led to the adoption of an open-core type, M i ,’* I Fm. 8. -rno'|'or»nAPn or 'rim EXrEm~ nnurnn s1'/\Nnnn.\'rnn\' AND Lmiirisn A VAVUUM numi ni' \\'sv|<:s mon A nlsrsrvr osi~n.- 1..\'i'ou»ins noni' |s_ IN Tins CME, sun- .m<"i‘u|_> To GREAT m,ec'rnir/\L rnessune. as a matter of course, and the val'i- ous diagrams of the figure referred to illustrate the modifications as v ‘/ _. § } - .2 I `; I ifgg- i 4 - -1 fl » E" 3, s \‘-.- _ .. . \ . °"' /WH IFIG. 7.*HSOME IiXI’l2`|l|M|'TN`\"E IN TF15|.A'F ]|.\H0|{A'|`()\i\` \VI'I`|\ ('I`|§|\‘EN'l`S OF HIGH l‘<\'m4;N'1‘I.\1.ANlJ Ilmn |<'|:nQ\vnN1'Y"-HX|'Hnl|\rEN'1' sno\\'IN n\' irnlc W.\Vics OP A l»|sT,\N'r <»s('lI.I.A‘|'.vUs'r1%lv To 'rim C1\l‘A(‘IT\' UF 'rniz uo1»\' UF 'ruin |>i'i<;u.\1‘0R_ WHO l’HEsEn\'|'Is Illxlsmm Fu0M INJURY n\' xl/\IN'|'AIN¥XG A I’i»:=l'l‘|uN AT 'rllli Nol»\L I‘o|N'l'_ \\'n1§uE THR lNT|‘1NFlE Vlnlm- TION is I.\TTI.l1L lflCl,’l'-'rnE l’RI-isslvnlc HN "rim NND mf THE (‘0I|."ro\vARDR 'HIE uI¢:,\m€R, \\'|lir'|| is lI.l.Ux|iNA'rln. 'l'|\eui‘idm\tlimitations TIIE \'\»\\EIc1fUI. f<'l`n|1:Al\iEm1, ls NEARLY they were gradually made in the manner of insulating and winding of the euils. ln diagram 2 the old, priinitiro u|etho<>il_ were resorted to, whieli \\`(‘I'L; linally disvarded. and so the coil shown in iliagrmn 8 re- sulted, whieh I have described on several oeeasinns and whieli, of all other constructions, ,permits the ob- tainment of the highest possible ten- sion with a two»terininal coil in a given space. , linteven in this perfected type it was not possible to go beyond a certain potential difierenee, and a further investigation led to a new type, which I have called a single terminal eoil, and which is illustrated in diagram 5) and is now well known, In this Coil the &l.ii_iLlSllI1(’1ltlS so made that the second- ary is nearly equal to a quarter of the ware length, the highest potential being. under these conditions, pro- is K I f 1 fmxqlx ¢,,l’Q 4 ‘ "3 . I ' ‘vis ii . . ,; 5 si 1 ‘ . *XAQ @ 1 I . i mu~,m pw' u Flu. 10.-IN THIS ExI'EluM|£N'r 1‘l|l¢0I‘F;1cATuli’:4 nobr is L'n.\n1:E!» 'ru A uul\2A1‘ PRESSUIUC DY A UIREVT f‘oNNE('TIoN \\'lTn AN 0s\`ILI.A'|'1wn»'|n|-2 l"nu1`uf¢li,\I‘1| slluwf-\ A frm. DU(?'|`INu BAR, (1/\Rn\'lN0 ON Tun END A slllal-:T or 'HN UF D\§'l`lcu\|lNl€1> Rlzii, HELD IN HAND-’l‘lIE ni’ERATOn IS ON THE Toi’ me A s'r,\'rmN.\n\' |£l.|£Lt'rlNE (nr Tim VA(‘U\':\l 'runlcs Usnn iN I.u:n'rlNu '1|ll<1LAm>n,\- '1'rinY_ 1'llonGI[ J\'r (‘0NsmlsRAnI.E 1v1s'rANf‘n oN 'rnic <‘|41iI,iNu, <:I.o\vs nl

March 29, 1899 ELECTRICAL REVIEW During these ellorts I fortunately rapidly with the rarefactiop of the at- discoveroil thc important part which mosphere and augmentation ol` tho "- ,, "' ______.,~: t it v _,ra / Q '” l' 4 *iw E _,_lt_ I I ° 1 1 ` f ‘ir \D I J ll \ ul i ‘ § I I \ ? /A . Fm. 9.~“soMl<1 ltxrnuiiul-1N1`S IN '|‘EsIiA’s LAnoHA'|‘0|t\' \\'lrH (‘I`IlI{l‘lN'I`S or HIGH l'0'1'ENTI,\i. Ann HmH F|mQnmNCY"»'rIlI\', IN 'rllls Ex\’E1tIMENT, is ('H,\HfH<1n To, A HIGH I'o1'|<1N‘1'I.\l. HY MEANS (nf A Coil. itI&sI’0NslVE To Tlllt WAVES '|'u.\Ns!\liT'1'l-in 'ro rr rum! A lHs'rAN'l` usCl|.l,,\’rUlt, AND A LUNG 1\l.Ass TUBE WAVED IN 'rlll-1 HAND is LHIHTEU 'ro GIKIQA1' nHll.LIANl‘Y n\' THE ElIl\'. air played in the breaking down ol' tho insulation, and by adopting proper methods for the exclusion ol gaseous matter. I was able to increase the electro-motive force to more than 10 times the value without breaking down the secondary. I have dc- serilied this method since, which I am using in thc manulaclurc of coils without which and nomlenscrs, ami it would he entirely impossible to reaeli any such results as I have ob- tained. 'l`hc industrial world has profited hy thc recognition of the action of the air. for it has helped to extend power transmission to greater distances than heretofore practicable. It has also been nsel-ul in determining the limits of tho electro-motive forces with ordinary apparatus used in power transmission, but I see that no attempt is yet made to overcome the streamers by a suitable construction of the cahles, as I have indicated, and thus make higher electro-motive forces available. Furtlier experimentation with the original single-terminal coil, before referred to, Gnally led step by step to the adoption ol' a coil of large dimcn- sions, which, in two typical forms, is illustrated in diagrams 10 and 11. With such a coil l found that there was practically no limit to thc tension obtainable, and-lt is hy its means that I discovered the most important of all facts arrived at in the course of my investigation in these lields. One of those was that the atmospheric air, though ordinarily a perfect insulator, conducted freely the currents of im- mense electro-motive force producible by such coils and suitable accessories. So great is the conductivity of the air, that the discharge issuing from a single terminal behaves as if the at- mosphere were rarelicd. Another fact is that this conductivity increases very electrical pressure, to such un extei it air as through a copper wirc. Follow- ing up these promising revelations I demonstrated conclusively by experi- ments that great amounts of electrical energy can be transmitted to any dis- tance through upper air strata which are easily accessible, and since this truth has been recognized every fiber has been strained to realize such a transmission on a large scale, 'l`l\ese two observations explain clearly the si- lent discharges noted frequently in dense air strata, but three or four miles above the eartlfs surface. One more equally important fact I may mention, which was simultaneously observed. The discharges of such a coil, when of an electro-motive force of a few millions of volts, excite powerful atlinities in the atmospheric nitrogen, causing it to combine read- ily with the oxygen and other ele- ments, particularly in the presence of aqueous vapor. So energetic are these actions and so strangely do such powerful discharges behave, that I have often experienced a fear that the atmosphere might be ignited, a terrible possibility, which Sir William Crookes, with his piercing intellect, has already considered. Who knows but such a calamity is possible ? And who can tell with ecrtitnde that periodical cessations of organic life on the globe might not be caused bv that M l1“"0m€l3"lC I“'@S5“"0B Wlllcll ignition of the air and destruction of 197 will lic for centuries unall`ected in contact with oxygen. but the com- bustion once started, the process con- tinues as long as there are elements to combine. While improving the construction of the transformers, every effort was made to perfect the apparatus for generating: tho currents. The oh- jectivo point from tho outset was to obtain the greatest possible rale of variation. High-frequency alterna- tors were iirst used, but their limita- tions were soou apparent. I then turned again to make and break de. vices, chiefiy with ‘the object of using them in connection with a novel form of transformenwhieh I have previously described, and which is now well known and understood. In its origi- nal form, as I Erst showed it, it is illustrated in diagram 12, which need not be dwelt upon, beyond saying that one of the characteristic features of such an instrument is the energiz- ing of the primary of the induction coil by the rapidly succeeding dis- charges of a condenser. In a more recent type, specially adapted for ordinary supply circuits, which I have described and shown before several scientific societies, the trans- former comprises, as indicated in diagram 13, three coils, there being, in addition to the primary and second- ftry.coils, one which receives the cur- ~ ,E ` . ' _ _ f' - ,,,=_;;;;_=:;‘- I-5-_ » ` tk, .5 ~» , _ ,~, ~` gt; _ ,ZH gui: ~ . ‘}5__é5‘L W . ‘ ;Z .' " ~ 53, ” ; -:fag g ' _ . u~ ni, . 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'_ f ,_ y i I l\\ I \ \ 1 , I I I \ `\ _ ._ i I ll » , _ - _ i , I i J 1 \ i _ I / ‘~ (r\ ~ _ » _ I 1 ’ \ , I { l , I' _ _ _ l I , \ git- - '_ "ll l t _ ‘ ' \ " 2 _ Iurmmmnv FIU. lli*-l’l\(\'fU|'lltA\"I[ OF AN A("r|\'E 'l`EIIMINAI| or AN IIlIl’I(0V`ED UECIIILATOR, USED IN '1'EEI1AlS EXVERIMIJINTN FUR T1lANFMI'l"l'lNG Hi,E(‘1‘HI<'M. EN!-lucy To urmA'|‘ UIsTi\:v('I;s \\'I'rHoUT WIRES-WIDTH OF ILLUMINATEU sI‘A&'E IR 18 I-‘EET~TlIE PHESSUBE oN 'rH|<: 'rn|n||NAi. is /\nol"r mu1lT MILLION Vo!/l‘s_ permit of no transit of ordinary cur- its life-sustaining qualities, accident- rents from the supply circuit, and is rcnls, those gciieraterl by auch u coil ally or as a consequence of some ac- designated the charging coil. Pref- pass with great 1`reedo1u through the cumulative change ? A lump of coal (¢,,,,,1,,,,e,, ,,,, mg, ,0,_,

204 TESL/\'S LABORATORY EXPERI- HENTS. fcmwzmzfa from page mm erably the latter is not in inductive relation with the former. On a num- bcr of occasions l have described high- frcqlienoy apparatus cnibomlyinr this lieautilul method, which luis allready been of great value to science in my hands as well as in those of others. Hut a defect, to which I called atten- tion early, still confronted me. It lay in the make and break devices which performed the function of charging and discharging the con- denser. Many of such devices, based on a variety of principles, formed the subject of experiments carried on with the aim of doing away with this imper- fection. To cite one of these, the current from the source of supply was passed through a minute column of conducting liquid main- tained in a variety of ways, and in this simple manner rapidly succeed- ing impulses were obtained. Inci- dcntally, some useful results were secured with these contrivances, as, for example, the generation of cur- rents of diifering phase and the pro- duction of rotating fields moving with constant velocity; but, inter- esting us these simple devices were. they naturally precluded the possi- bilityofeconomicalconversion. Their study, ho\vever, was useful as a means of recognizing the re uire- ments of such make and breailr ap- paratus, and, finally, led to forms based on scientific and economical principles. A number of these were recently described in tech- nical periodicals and, asrstated on a former occasion, they fulfill their dilllcult 'duty surprisingly well and make it` possible to obtain cur1‘ents of very high frequency from ordinary supply circuits with great economy. These novel contrivances lend them- selves well also to the uses of the ordinary induction coil, and I have employed them with' cqual success in a form of I’lauté’s rheostatic machine and for many other useful purposes. Thus, after a continuous effort ex- tending through a number of years, I have the supreme satisfaction of having carried this hard and im- portant task ‘to a satisfactory end. The annexed photographs will serve to convey an idea of what can be done with these perfected implements. Referring to Fig. l, illustrative of the high rate of change obtained in the current, a vacuum bulb of 'about 12 inches in diameter is held in front of a coil of four turns of specially constructed' heavy cable, through which a condenser is discharging, and, although at a distance of several inches from the coil, the gas in the bulb is brought to intense incandes- cence, the light emitted being fully equal to 1,500 candles. Such a powerfully energized coil, when the frequency, as in this instance, is measured in millions per second, shows littlc repellent action, /ut when the frequency l the impulses is low, closed con- Auctors, us washers of conducting material, are thrown off with a force of a magnitude which can be only ELECTRICAL REVIEW explained on the assumption that the currents have maximum values of many hundred thousand amperes. The remaining photographs will be understood from the titles, which are made explicit for this purpose. I hope to have in the near l'uture an opportunity for describing more of such experiments, and dwelling in detail on tlieapperatusfused. For the present I am compelled, for,want of time, to merelystate that' the vibrations used in most of them were from 400,000 to 800,000 per second. In conclusion I wish to apologize for the 'frequent appearance of my likeness 1n‘ tliese photographs, which is distasteful to`me, but was unavoida- ble. Most of the ad vxinces indicated, and a number of others, have resulted from the application.of 'the' beautiful principle' upon which the operation of tllisapparatus is'-'based_.` Scientific men have honored nie byideutifying it with my namefand l'have earnestly endeavoredto show myself-worthier of tl\is great distinction by devoting to it much of my energies. No desire for rnaterial advantages has animated me in all this work, though I hope, for the sake of the continuance of my labors, that these will soon follow, nal- urally, asa compensation for valuable services rendered to science and in- dustry. To the scientific experts, who‘are familiar, in _theory and ex- periment, with electrical vibrations, the results here shown ‘will, I be- lieve, speak in eloquent language. But those readers tojvhom they are naturally less' intelligible will ask: What are they good ‘for, and what do they or have they demonstrated ? 'l`o them it may be said that they have shown and proved among many other things; That ordinary currents can be transformed with h¥h economy into electrical vibrations of any pitch, which are needed 'in many nove arts; they have shown thatelectrical energy in great amounts can be efficiently and safely transmitted without the use of wires to any point of the globe, how- everdistaut; they have furnished proof that the movements' and operation of bodies and machinery carried by the same can be controlled from a great distance without any tangible con- nection whatever and with absolute precision; they have proved the prac- ticability of asystem of signaling with- out wires, not with the imperfect appliances as before attempted, which can not be tuned and are rendered useless by the play of a small induc- tion coil, but by means of apparatus producing powerful oscillations and circuits in exact synchronism, with which it is impossible to interfere; they have shown that atmospheric nitrogen can be readily combined and valuable products rnanuhxctured, merely by the application of cheap water power, and that light, diffusive likethat of the sun, can be produced with an economy greater than obtain- able in the usual ways and with lamps that never consume. N. -'l`ESLA'. New York, March 26. _,QT