llTGll FREQUENCY AND HIGH POTENTIAL CURRENTS. 123

a means of converting direct or alternating currents. In thisconnection Mr. Tesla advocates the perfecting of apparatus capa-ble of generating electricity of high tension from heat energy,believing this to be a better way of obtaining electrical energyfor practical purposes, particularly for the production of light.

While many were probably prepared to encounter curiousphenomena of impedance in the use of a condenser dischargeddisruptively, the experiments shown were extremely interestingon account of their paradoxical character. The burning of anincandescent lamp at any candle power when connected across aheavy metal bar, the existence of nodes on the bar and the possi-bility of exploring the bar by means of an ordinary Cardewvoltmeter, are all peculiar developments, but perhaps the mostinteresting observation is the phenomenon of impedance observedin the lamp with a straight filament, which remains dark whilethe bulb glows.

Mr. Tesla’s manner of operating an induction coil by means ofthe disruptive discharge, and thus obtaining enormous differencesof potential from comparatively small and inexpensive coils, willbe appreciated by experimenters and will find valuable applica-tion in laboratories. Indeed, his many suggestions and hints inregard to the construction and use of apparatus in these investi-gations will be highly valued and will aid materially in futureresearch.

The London lecture was delivered twice. In its first form,before the Institution of Electrical Engineers, it was in somerespects an amplification of several points not specially enlargedupon in the .New York lecture, but brought forward many addi-tional discoveries and new investigations. Its repetition, inanother form, at the Iioyal Institution, was due to Prof. Dewar,who with Lord Rayleigh, manifested a most lively interest in Mr.Tesla’s work, and whose kindness illustrated once more the strongEnglish love of scientific truth and appreciation of its votaries.As an indefatigable experimenter, Mr. Tesla was certainly no-where more at home than in the haunts of Faraday, and as theguest of Faraday’s successor. This Royal Institution lecturesummed up the leading points of Mr. Tesla’s work, in the highpotential, high frequency field, and we may here avail ourselvesof so valuable a summarization, in a simple form, of a subject byno means easy of comprehension until it has been thoroughlystudied.