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INVENTIONS OF NIKOLA TESLA.

been noted by many experimenters, but in my experiments theeffects were much more powerful than those usually noted.

The following is the communication 1 referred to :—

“Mr. Tesla seems to ascribe the effects he observed to electrostatic action,,and I have no doubt, from the description he gives of his method of conduct-ing his experiments, that in them electrostatic action plays a very importantpart, tie seems, however, to have misunderstood my position with respect tothe cause of these discharges, which is not, as he implies, that luminosity intubes without electrodes cannot be produced by electrostatic action, but that itcan also be produced when this action is excluded. As a matter of fact, it isvery much easier to get the luminosity when these electrostatic effects are-operative than when they are not. As an illustration of this I may mentionthat the first experiment I tried with the discharge of a Leyden jar producedluminosity in the tube, but it was not until after six weeks’ continuous experi-menting that I was able to get a discharge in the exhausted tube which I wassatisfied was due to what is ordinarily called electrodynamic action. It is ad-visable to have a clear idea of what we mean by electrostatic action. If,previous to the discharge of the jar, the primary coil is raised to a high po-tential, it will induce over the glass of the tube a distribution of electricity.When the potential of the primary suddenly falls, this electrification will re-distribute itself, and may pass througli the rarefied gas and produce luminosityin doing so. Whilst the discharge of the jar is going on, it is difficult, and,from a theoretical point of view, undesirable, to separate the effect into parts,one of which is called electrostatic, the other electromagnetic ; what we can-prove is that in this case the discharge is not such as would be produced byelectromotive forces derived from a potential function. In my experiments the-primary coil was connected to earth, and, as a further precaution, the primarywas separated from the discharge tube by a screen of blotting paper, moistenedwith dilute sulphuric acid, and connected to earth. Wet blotting paper is asufficiently good conductor to screen off a stationary electrostatic effect, thoughit is not a good enough one to stop waves of alternating electromotive intensity.When showing the experiments to the Physical Society I could not, of course,keep the tubes covered up, but, unless my memory deceives me, I stated theprecautions which had been taken against the electrostatic effect. To correctmisapprehension I may state that I did not read a formal paper to the Society,my object being to exhibit a few of the most typical experiments. The ac-count of the experiments in the Electrician was from a reporter's note, and wasnot written, or even read, by me. I have now almost finished writing out, andhope very shortly to publish, an account of these and a large number of alliedexperiments, including some analogous to those mentioned by Mr. Tesla on theeffect of conductors placed near the discharge tube, which I find, in somecases, to produce a diminution, in others an increase, in the brightness of thedischarge, as well as some on the effect of the presence of substances of largespecific inductive capacity. These seem to rue to admit of a satisfactory ex-planation, for which, however, I must refer to my paper.”

1. Note by Prof. J. J. Thomson in the London Electrician , July 24, 1891.