Editorial: Mr. Tesla's Lecture

Wednesday, July 8, 1891
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32 THE ELECTRICAL ENGINEER. [July8,1891. THE ELEcTR1C{-\L ENGINEER. PUBLISHED EVERY WEDNESDAY AT 150 Broldvlly, Noi York UII1. Tslspllone: 3800 Cortllndt- Ulblo Addrall: LEIQGINEEIK. Guo. M. PHILIPS, President. F, R. CuLv||l, Tren. and Business Manager Edited bv T. Conunvonn Mun-nn ann josnrn Wrrun. Assn. Editor: Gloss! H. MULDAUK. New England Editor Ind Mlnlger, A. C. SHAW, Room 10-610 Atlantic Avenue Bolton. Man. Western Editor and Manager, W. Forman Ca|.\.n|s, 347 The Rcukery, citings, ni. New vm-k Agn", M. c. sm.|.w/is; iso amduy. Phflldelphll Agent, W. F. HANIA, 'IU Glrlrd Building. 'Illllli Ol BUBSUBIPTIOH. POSTAGE PREPAID. United Bl-lies and Cmldl. - - - per nnnnm, |100 Fonr nr more Copls, ln Clubs (each) - ~ “ 2.60 Brest Brftsln md other Foreign Countries within the Postal Unltm “ 5.00 Single Coyle. - - - ~ - - -10 [Enund aa nwndalaumatural Du Nm York, M X. Pon Opke. Aprtl D, 1888.1 EDITORIAL ANNOUNCEMENTS. 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NO. 166. 1: 1. me enough fm- a physical tavsguglmfm min we ha vs me stmplo ram, which may be ernbodied inamarlienumear equamm; we ma.: see ei",-lv In the mrmrf, eye the opsmnom in nam", and now ilislfnemmmm an proauesa ru um-afmes tuna the w¢zz-know" :mu of fm-as and momm.-.1a»¢pl» umm. MR. TESLA`S LECTURE. OW that we have the full text of Mr. Tesla’s paper before us, we are better able to judge of t.he char- acter and scope of his work. The ground covered by Mr. Tesla is so vast that even in his somewhat extended paper he has, as he states, only been able to pay passing notice to many facts, each one of which might have been made the subject of a separate paper; and it is to be hoped that he may shortly find time to enter more into the detail of the various points brought out. Although Mr. Tesla’s work has relation to many matters of the highest importance and discloses some startling possibilities, yet its immediate bearing on the question of producing light economically is perhaps that which will appeal most strongly to the electrical engineer. 'Taking up the course of reasoning followed by Mr. Tesla, it will be noted that he started out with the recognition of the fact, which he has now experimentally demonstrated, that for the production of light waves, primarily, electro- static effects must be brought into play, and continued study has led him to the opinion that all electrical and magnetic effects may be referred to electrostatic molecular forces. This opinion finds a singular confirmation in one of- the most striking experiments which he describes, namely,-the production of a veritable dame by the agita- tion of electrcstatically charged molecules. It is of the highest interest to observe that this result points out a way of obtaining a flame which consumes nn material and in which no chemieztl nctinn whatever takes place. lt also throws a light on the nature of the ordinary flame, which Mr. Tesla believes to be due to electrostatic molecular actions, which, if true, would lead us directly to the idea that even chemical affinities might be clectrostnt.ic in their nature and that, ns has alreally been suggested, molecular forces in general may be refcrable to one and the same cause. This singular phenomenon accounts in a plausible manner for the unexplained fact that buildings are fre- quently set. on fire during thunder-storms without having been :it all struck by lightning. lt may also explain the total disappearaxiee of ships at sea. One of the striking proofs of the correctness of the ideas advanced by Mr. Tesla is the fact that, notwithstanding the employment of the most. powerful 0l0Ci,I'0Ill$lgl\0frll} in- ductive effects, but feeble luminosity is obtainable, and this only in close proximity to the source of disturbance ; whereas, when the electrostatic effects are intensified, the some initial energy sullices to excite luminosity at consider- able distances from the source. That there are only elec- trostatic effects active seems to be clearly proved by Mr. Tesla’s experiments with an induction coil operated with alternating currents of very high frequency. He shows how tubes may be made to glow brilliantly at. considerable distances from any object when placed in a powerful, rapidly alternating, electrostatic field, and he describes many interesting phenomena observed in such a field. His experiments open up the possibility of lighting an apart- ment. by simply creating in it such an electrostatic field, and this, in a certain way, would appear to be the ideal method of lighting a room, as it would allow the illuminat- ing device to be freely moved about. The power with which these exhausted tubes, devoid of any electrodes, light. up is certainly remarkable That the principle propounded by Mr. Tesla is a broad one is evident from the many ways in which it may be practically applied. \Ve need only refer to the variety of the devices shown or described, all of which are novel in character and will, without doubt, lead to further import- ant results at the hands of Mr. Tesla and other investigat- ors. The experiment, for instance, of lighting up a single filament or block of refractory material with a single wire, is in itself sufiicient,to_give Mr. 'l`esla’s work the stamp of originality, and the numerous other experiments and effects which may be varied at will are equally new and interest- ing. Thus, the incandescent filament spinning in an unex- hausted globe, the well-known Crookes experiment on open circuit, and the many others suggested will not fail to in- terest the reader. Mr. Tesla has made an exhaustive study of the various forms of the discharge presented by an in- duction coil when operated with these rapidly alternating currents, starting from the thread-like discharge and pass- ing through various stages to the true electric dame. A point of great importance in the introduction of high tension alternating current which M. Tesla brings out is the necessity of carefully avoiding all gaseous matter in the high tension apparatus, 1Ie shows that, at least with very rapidly alternating currents of high potential, the discharge may work through almost any practicable

JUlYB,139l-] THE ELECTRICAL ENGINEER. 33 thickness of the best insulators, if air is present. In such cases the air included within the apparatus is violently agitated and by molecular bombardment the parts may be so greatly heated as to cause a rupture of the insulation. The practical outcome of this is, that, whereas with steady currents, any kind of insulation may be used, with rapidly altemating currents oils will probably he ihe best to em- ploy, a fact which has been observed, but not until now satisfactorily explained. The recognition of \he above fact is of special importance in the construction of the costly commercial induction coils which are often rendered use- less in an unaccountable manner. The truth of these views of Mr, Tesla is made evident by the interesting ex- periments illustrative ofthe behavior of the air between charged surfaces, the luminous streams formed by the charged molecules appearing even when great thicknesses of the best insulators are interposed between the charged surfaces. These luminous streams afford in themselves a very interesting study for the experimenter. \Vith these rapidly alternating currents they become far more po\ver- ful and produce beautiful light effects when they issue froma wire, pinwhecl or other object attached to a ter- minal of the coil; and it is interesting to note that they issue from a ball almost as freely as from a point, when the frequency is vcry high. From these experiments we also obtain a better idea of the importance of taking into account the capacity and self-induction in the apparatus employed and the possibili- ties offered by the use of condensers in conjunction with alternate currents, the employment of currents of high fre- quency, among other things, making it possible to reduce the condenser to practicable dimensions. Another point of interest and practical bearing is the fact, proved by Mr. Tesla, that for alternate currents,‘especially those of high frequency, insulators are required possessing a small specific inductive capacity, which at the same time have a high insulating power. Mr. Tesla also makes interesting and valuable sugges- tion in regard to the economical utilization of iron in machines and transformers. He shows how, by maintain- ing by continous magnctization a flow of lines through the iron, the latter may be kept near its maximum permea- bility and a higher output and economy may be secured in such apparatus, This principle may prove of considerable commercial importance in the development of alternating systems. Mr. 'l`csla’s suggestion that the same result can he secured by heating the iron by the hysteresis and eddy currents, and increasing the permeability in this manner, while it may appear less practical, nevertheless opens another direction for investigation and improvcnnent. The demonstration of the fact that with nltr-rnating cur- rents of high frequency sulliuient energy may be ll'&llB- mitted under practicable conditions through the glass of an incandescent lamp hy electrostatic or electromagnetic in- duction mayleanl to a departure in the construetiuii uf such devicces. Another important experimental result achieved is the operation of lamps, and even motors, with the dis- charges of condenscrs, this method atfording a means of converting direct or alternating currents. ln this connec- tion Mr. Tesla advocates the perfecting of apparatus cop- able of generating electricity of high tension from heat energy, believing this to be a better way of obtaining elec- trical energy for practical purposes, particularly for the production of light. While we were prepared to encounter curious phenomena of impedance in the use of a condenser discharged disrup- tively, the experiments shown were extremely interesting on account of their paradoxical character. The burning of an incandescent lamp at any candle power when connected across a heavy metal bar, the exist- ence of nodes on the bar and the possibility of exploring the bar by means of an ordinary Cardew voltmeter, are all curious developments, but perhaps the most interesting observation is the phenomenon of impedance observed in the lamp with a straight filament, which remains dark while the bulb glows. Mr. '1‘esla’s manner of operating an induction coil by means of the disruptive discharge, and thus obtaining enormous differences of potential from comparatively small and inexpensive coils, will be appreciated by experimenters and will find valuable application in laboratories. Indeed, his many suggestions and hints in regard to the construc- tion and use of apparatus in these investigations will be highly valued and will aid materially in future research. Looked at from the standpoint of scientific research we believe that Mr. Teala’s paper will be conceded to be one of the most remarkable productions of recent years, and worthy of avery high rank among the classical publications on electricity. In addition to its great scientific value,how. ever, it opens up possibilities not only in the production of light, but of power, the contemplation of which, as Mr. Tesla eloquently puts it, “ expands our minds, strengthens our hopes and fills our hearts with supreme delight.”