PATENTED APR. 18, 1905.

No. 787,412. N. TESLA.

ART OF TRANSMITTING ELECTRICAL ENERGY THROUGH THE NATURAL MEDIUMS. APPLIOATION PILBD .MAY 16, 1900. RBNBWBD JUNB 17. 1902 •

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.i'atentea April 18, 1905.

No. 787.412.

UNITED ST ATES NIKOLA TESLA, OF

P A fENT Nr~W

OFFICE.

YOHK. !\, y,

ART OF TRANSM ITTI NG ELECTRICAL EN ERGY TH ROUGH TH E NATU RAL MEDI UMS, SPECIFICATION forming part of Letters 'Patent No, 787,'112, dated April 18, 1905. Application filed May 16, 1900, Renewed June 17, 1902, Serial No, 112,034,

nU whmn it 71U~!I rO/WfTn: Be it known that I, ~iKOLA TI'~SLA, a citizen of the United States, residing)n the bOl"Ough of Manhattan, in the city, county, and State 5 of New York, havediscovered a new and useful 1m pt'ovement in the Art of Transmitting ElectricalEnerg,V Through the Natural Media, of which the following is a specitieation, reference being had to thedrawingsaccompanxing I c and forming a part of the same, 1t is known since a long time that electric . currents Tllay be propagated through the eal,th, and this kn{)wleclg'e has been ·utilized in man,\, ways in tl)(~ tl'ansmission of signals IS and the operation .of a variety of receiving devices remote from the SOllrce of energy, mainly with the object of dispensing with a return conducting-\vire, It is also known that electrical disturhances may be transmitted 20 through portions of the parth hy grounding only one of the poles of the source, and this fact I have macle use of in systems which I have devised for the purpcJses of transmitting through the natumf media intellig'ible signals 25 or· power and which are now familial'; \)ut all exppriments and obsen'ations heretofore macle have tended t,o contiI'm the opinion held by the majority of scientific men that the eal,th, owing to its immense extr}nt, although pos30 sessing conduct.ing propel't.ies; does not beluwe in tho manner of a conductor of limited dimensions with respec.t to the disturbances produced, but, on the contl'ary, mu:ch like a vast. I'eservoi I' 01' ocean, \vhich while it may be 35 locally distUl'bed b,,,a commotion of some kind remains unresponsive and quiescent in a large pat't or as a whole. Still anothet' ,fact now of common knowledge is that when electrical waves or oscillations'are impressed upon 40 such a conducting-path as a metallic wire reflection takes place under certain ,condition!> from the ends of the wire, and in consequence of the interfet·ence.of the impressed and reflected oscillations t.he phenomenon of "sta-1-5 tionary waves" with maxima and minima in detinite tix~d,positioris ·is produced. In an,Y casethe exisbenc.eo£ these waves indicates that someLof~the outgoing waves have reached the boundaries of the coriducting-path and' have 50 beeh reflected £I·om· the same. Now 1 have ';.'0

discovered t.hat llotwit.hstnniling its nts(. dimensions and cont.ral'\' to all ohservations heretofore made the te'n'estrinl globe lIlay in a large part or as a whole bphllTe towltl'll dist'urbances impressed UpOll it ill t.lw sltllle man- 55 ner as a conductor of limitnil size, this fact being demonstratNI by llon,1 phnllollWnlt, which 1 shall hereinaftm' (k..;;c:ri hi', In the course of eert.aln ill\'(~stigatiolls which I eal'l'ied on for the purposl' of st.udying' 60 the effects of light.ning discharges IIpon the electrical condition of (,he earth I ohsen'ed that sensitive l'(~eei\-ing instrlllllentsar'I'angt'd so as to be capable of respollding' to {'l(~etrieal, dist.nrbances created hy t.he discllarg'(ls at 65 times failcll to resl)()nd when tlwy should Illwe done so, amI upon inqlliring into the callses of this unexpected behavior I discovered it to be due to the character of the dect.r'ical waves which wel'e proclueel[ in the eart.h by the 70 lightning discharges and wlrieh had nodalregions following at definite distances the shifting source of the disturbances. From data obtained in a large number of obse'rvations of the maxinut and minillla of these waves I 75 found their length to var,V aplll'oximatei,v hom twenty-five to seventy kilo!1lptet·s, and these results and certain theoret.ical,deductions led me to the conclusion that waves of this kind may be propagated in all directions 80 'over the globe and tha.t they may be of still more widely differing lengths, the ('xtremp,1 i mits being imposer[ by the physical dimensions and properties of the eal,th, Rncogn izi ng in the existence of these waves an unmistakable m-i- 85 dence that the disturbances created hltd been conducted hom their origin to the most remote llOrtions of the globe and had been thence reflected, I conceived the idea of producing such waves in the earth by artificial 90 means with the object of utilizing them feW many useful purposes for which they are or might be found applicable, This lll'oblem was rendered extremely difficult owing to the immense dimensions of the planet, Imel conse- 95 quently enormous mo\-ement of electricity 01' rate at which electrical energ.Y had to be delivered in order to approximate, even in a remote degree, nlQ\Tements or rates which are manifestly attained in the displays of e1ec- 100

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trical forces in nature and which seemed at first unrealizable hy any human agencies; but b.y gradual and continuous improvements of a generator of elect,rical oscillations, which I 5 have described in m.y Patents Nos. 645,576 and 649,621, I finally succeeded in reaching electrical movements or rates of delivery of electrical energy not only approximating, but, as shown in many comparative tests and 10 measurements, actually Rurpassing those of lightning discharges, and by means of this apparatus I have found it possible to reproduce whenever desired phenomena in the earth the same as or similar to those due to such I S discharges. With the knowledge of the phenomena discovered by me and the means at command for accomplishing. these results I am enabled not only to carry out manyoperations by the use of known instruments, but 20 also to offer a solution for many important problems involving the operation or control of remote' devices which' for want of this knowledge and the absence of these means have heretofore been entirely impossible. For 25, example, by the use of such a generator of stationary waves and receiving apparatus properly placed and adjusted in any other locality, howe-vel' remote, it is practicable to transmit intelligible signals or to control or 30 actuate at will anyone or all or such apparatus for many other important and valuable purposes, as for indicating wherever desired the correct time ·of an observatory or for ascertaining the relative position of a body or 35 distance of the same with reference to a given point or for determining the course of a moving object, such as a vessel at sea, the distance traversed by the same or its'speed, or for producing many other useful effects at'a distance 4 0 dependent· on the intensity, wave length, direction or velocity of movement, or other feature or property of disturbances of this character. . I shall typically illustrate th~manner of ap4S plying my discovery by cW.8cribing one of the specific uses of the same-namely, the transmission of intelligible signals or messages between distant points-and with this object, reference is now made to the accompanying draw50 ings, in whichFigure 1 represents diagrammatically the generator which produces stationary waves in the earth, and Fig. 2 an apparatus situated in a rHmote 10cality' for recording the effects of 55 these waves. • In Fig. 1, A designates a primary coil forming part ofa transformer and consisting generall.y of a few turns of a stout cable of inappreciable, resistance, the ends of which are 60 connected to the terminals of a source of powerful electrical oscillations"diagrammaticall.y represented by B. This source is usuall.y a condenser charged to a high potential and discharged in rapid succession through the pri65 mar.y, as in a type of transformer invent'ed

m' me and not well known; but when it is de:;;[red to produce stationary waves of great lengths an alternating dynamo of suitable construction may be used to energize the primary A. C is it spirally-wound secondary coil within the primary having the end nearer to the latter connected to the ground E' and the other end to an elevated terminal E. The physical constants of coil C, determining its period of vi bration, are so chosen and adjusted that the secondary system E' C E is in the closest possible resonance with theoscillations impressed upon it by the primary A. It is, moreover, of the greatest importance in order to still further enhance the rise (if pressure and to increase the electrical movement in the secondary system that its resistance be as small as practicable and its self-induction_ as large as possible under the conditions imposed. The ground should be made with great care, with the object of reducing its resistance. Instead of being directly grounded, as indicated, the coil C may be joined. in series or otherwise to the primary A, in which case the latter will be eonnected to the plate E'; but be it that none or a part or all of the primary or excit,ing turns are included in the coil C the total length of the conductor from the ground-plate E' to the elevated terminal E should be equal to one-quarter of the wave length of the ele,ctrical disturbance in the system E' C E or else equal to that length multiplied by an odd number. This relation being observed, the te.t:minal E will be made to coincide with the points of maximum pressure in the secondary or excited circuit, and the greatest flow'of electricit.y will take place in the same. In order to magnify the electrical movement in the secondary as much as possible, it is essential that its inductive c(innection with the primar.y A should not be very intimate, as in ordinar.v transformers, but loose, so as to permit free oscillationthat is to say, their mutual induction should be smalt The spiral form of coil C secures this advantage, while the turns near the,primary A are subjected to a strong inductive action and develop it high initial electromotive force. These adjustments and relations being carefully completed' and other constructi ve features indicated rigorously observed, the electrical movement produced in the secondary system by the inductive action of the primal'.V A will be enormously magnified, the increase being directly proportionate to the inductance andfrequenc.v and inversely to the resistance of the secondary s.ystem. I have found it practicable to produce in this manner an electrical movement thousn.nds of times greater than the initial-that IS, the one impressed upon the secondary by the primary A--and I have thus reached activities or rates of flow of electrical energy in tlre s.vstem E' C E measured by many tens of thousaqds of horsepower. Such immense movements of elec-

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tricit.Y give rise to a \'}ll'iety of novel and I iycly to the ground and to an elevatc(1 t('rmistriking phenom'ena, among which arc thosc I nal and tuncd to respond morc efi'ect.in'ly to already described. Thc powcrful electrical : the oscillations. Another way is to COlllll't't osciIIations in the system E' C E being com- I a tuned circuit to the ground at two points 5 -Illunicated to tJ)('~',"Olllld cause cOl'respond- i lying more or less in a llleridian passing' 70 ing vibrations to be propagated to distallt i through the pole E' or, g'encmlly stated, to parts of the globe, whence they arc reflected; an,\" two points of a diffprent potential. and by interferencc with the outgoing' \-ilJl'nIn Fig, 2 I have sitown a dedce for detecttions produce stationary W~1\"es tJlP crcsts ing the l)l'esence of the Wfwes sllch as I ha \"(~ )0 and hollows of which lie in pal'allel ('ireles ! used in a nov~llllethod of mag·llif.ying: feehle 75 relativel,Y to which the grouml-plak K may: effects whieh I have described ill Ill,\' Patents be considered to be the pole. Stated other- Nos. 61:15,95:1 and 685,95;)_ It consists of ~1 wise, the terrestrial conductor is thrown into cylinder lJ, of , insulating material, which is resonance with the oscillations impressed moved at a uniform rate of sJleed by cloc!\:IS upon it just like a wire. }\lore tban.this, a work or other suitable motive power and is Ro number of facts .ascertained by mr: cleady pro\"iclecl with two metal rings F F', upon RlJOw that the movement of electricity through which bear brushes If and 1/, connected, 1'1'it follows certain laws with nearl,v111athemat- spccti\'ely, to the terlllinal plates P and 1". ical rigor. For the present it will be suffi- From the rings F J:;" extend narrow metallic 20 cient to state that the planet behaves like a segments.< and s', which h,\,thc rotation of 85 perfectly smooth 01' polished conductor of in- the' cylinder D ~lre hrought alternatd,V into appreciable resistance with capacit,Y and self contact with double 1>l'IIsl\(\s I, and //, cllrl'ipd induction uniformly' distributed along the b,yand in contact with cOllducting-hol(lm'sli axis of s,Ymmetryof wave propagation and and II:, sUPPol'ted in metallic bearings (; and 25 transmitting slow electrical oscillations with- G ' , as shown. The .latter arc connrcted to 90 out sensible distortion and attenuation. the terminals T alld '1" of a condenser II, and Bcsides the above thl'ee rer]uirelllents seem it should he understood that t.he,\' are capabk to be essential to the establishment of tl\(\ of angulal' displacelllPnt as ordinal',\" hl'ushresonating condition. supports, The object of IIsing' two brllshes, 30 First.. Theelu·th'sdiameterpassingthl'Ough as" and 1/, in each of thc holders II and // is 95 the polc should be an odd multi pIe of tlw to val',\' at will the d 1I1'ation of the electric conIlUal'ter wave length-that is, of the ratio be- tact of the plates P and pi with the terlllinals tween thevelocit,yof light·--and foul' times the T and '1", to which is connected a I'eceidngfre(IUenc,V 04' the currents. circuit. inclw.ling a l'ecl'in'I' R and a rlevicl' tI, 35 Second. It is necessary to employ oscilla- pel'f'orming tlw d IIty of closing' the l'ecei \'ing- 100 tions in which the ratc of radiat.ion of energy circuit at prerleterminrd intervals of t.ime and into space in the form of hertzian 01' electro- discharging the stored (,I1IWg',Y thl'OlIgh the 1'Pmagnetic wayes is \'CI'y small. To g'i\'e an ccivcl'. In the present case this d(wice conidea, I would say that the frequencj' should be sists of a cylinder' made part.ly ofcondnct.ing 4 0 smaller than twenty thousand pel' second, and partly of insulating mat.eriall' and ,,', rc- 105 though shorter waves might be lll'n.cticable.. specti vely, which is rotat.pd H t. tllP desired I'ate The iowest frer]uenc.r would appear t.o he six of spee(l by any suitahle Ilwans. Thn con1)01' second, in which case there will be but rlucting pal't, (. is in good elnC't.riC'al conned.ion one node, ator neal' thegrouml-plate. and, pltr- with the sh:tft S and is prO\-ided with tappr45 adoxical as it may seem, the e_ffect will increase ing segments ff', upon \\'.hich slidps a hrush 110 with the distance and will be greatest in a k, sUl>POltml on It conducting'-rod I, capahle region diametrically opposite the tmnsmitkr, of 10ngitudinalll.lIjustment in a metallic supWith oscillat.ions still slowet· the ealth, strictI,\" POlt /)1, Anothnr bl'l1sh, II, is lU'I'ang-pd t.o h