HIGH FREQUENCY AND HIGH POTENTIAL CURRENTS. 368

dinary coils, the speeds must, of course, be much greater whenthe bulbs are lighted from such a coil. Assuming the speed tobe as high as live kilometres and uniform through the whole'trajectory, as it should be in a very highly exhausted vessel, thenif the alternate electrifications of the electrode would be of afrequency of five million, the greatest distance a particle couldget away from the electrode would be one millimetre, and if itcould be acted upon directly at that distance, the exchange ofelectrode matter or of the atoms would be very slow and therewould be practically no bombardment against the bulb. This atleast should be so, if the action of an electrode upon the atomsof the residual gas would be such as upon electrified bodies whichwe can perceive. A hot body enclosed in an exhausted bulbproduces always atomic bombardment, but a hot body has nodefinite rhythm, for its molecules perform vibrations of all kinds.

If a bulb containing a button or filament be exhausted as highas is possible with the greatest care and by the use of the best ar-tifices, it is often observed that the discharge cannot, at first,break through, but after some time, probably in consequence ofsome changes within the bulb, the discharge finally passes throughand the button is rendered incandescent. In fact, it appears thatthe higher the degree of exhaustion the easier is the incandescenceproduced. There seem to be no other causes to which the in-candescence might be attributed in such case except to the bom-bardment or similar action of the residual gas, or of particles ofmatter in general. But if the bulb be exhausted with the great-est care can these play an important part ? Assume the vacuumin the bulb to be tolerably perfect, the great interest then centresin the question: Is the medium which pervades all space con-tinuous or atomic ? If atomic, then the heating of a conductingbutton or filament in an exhausted vessel might be due largelyto ether bombardment, and then the heating of a conductor ingeneral through which currents of high frequency or high poten-tial are passed must be modified by the behavior of such medium ;then also the skin effect, the apparent increase of the ohmic re-sistance, etc., admit, partially at least, of a different explanation.

It is certainly more in accordance with many phenomena ob-served with high-frequency currents to hold that all space is per-vaded with free atoms, rather than to assume that it is devoid ofthese, and dark and cold, for so it must be, if filled with a con-tinuous medium, since in such there can be neither heat nor light.