Nikola Tesla - Free-Energy Devices

11IG1I VllI&Q UENCY AND HIGH POTENTIAL CURRKltTS. 307through the bulb, because of the great density at the point ofcontact. .With low frequencies it seems that gases of greatatomic weight excite more intense phosphorescence than thoseof smaller weight, as for instance, hydrogen. With high frequenciesthe observations are not sufficiently reliable to draw aconclusion. Oxygen, as is well-known, produces exceptionallystrong effects, which may be in part due to chemical action. Abulb with hydrogen residue seems to be most easily excited.Electrodes which are most easily deteriorated produce moreintense phosphorescence in bulbs, but the condition is not permanentbecause of the impairment of the vacuum and the depositionof the electrode matter upon the phosphorescent surfaces.Some liquids,as oils, for instance, produce magnificent effects ofphosphorescence (or fluorescence but?), they last only a few{seconds. So if a bulb has a trace of oil on the walls and thecurrent is turned on, the phosphorescence only persists for a fewmoments until the oil is carried away. Of all bodies so far tried,sulphide of zinc seems to be the most susceptible to phosphorescence.Some samples, obtained through the kindness of Prof.Henry in Paris, were employed in many of these bulbs. One ofthe defects of this sulphide that is,it loses its quality of emittinglight when brought to a temperature which is by no means high.It can therefore, be used only for feeble intensities. An observationwhich might deserve notice is, that when violently bombardedfrom an aluminum electrode it assumes a black color, butsingularly enough, it returns to the original condition when itcools down.The most important fact arrived at in pursuing investigationsin this direction is, that in all cases it is necessary, in order to excitephosphorescence with a minimum amount of energy, to observecertain conditions. Namely, there is always, no matter whatthe frequency of the currents, degree of exhaustion and characterof the bodies in the bulb, a certain potential (assuming the bulbexcited from one terminal) or potentialdifference (assuming thebulb to be excited with both terminals) which produces the mosteconomical result. If the potential be increased, considerableenergy may be wasted without producing any more light, and ifit be diminished, then againthe light productionis not as economical.The exact condition under which the best result is obtainedseems to depend on many things of a different nature, and it is tobe yet investigated by other experimenters,but it will certainly