sphere, instead of being steady, is alternating, the conditions are entirely different.  In this case a rhythmical bombardment occurs, no matter whether the molecules after coming in contact with the sphere lose the imparted charge or not; what is more, if the charge is not lost, the impacts are only the more violent.  Still if the frequency of the impulses be very small, the loss caused by the impacts and collisions would not be serious unless the potential were excessive.  But when extremely high frequencies and more or less high potentials are used, the loss may be very great.  The total energy lost per unit of time is proportionate to the product of the number of impacts per second, or the frequency and the energy lost in each impact.  But the energy of an impact must be proportionate to the square of the electric density of the sphere, since the charge imparted to the molecule is proportionate to that density.  I conclude from this that the total energy lost must be proportionate to the product of the frequency and the square of the electric density; but this law needs experimental confirmation.  Assuming the preceding considerations to be true, then, by rapidly alternating the potential of a body immersed in an insulating gaseous medium, any amount of energy may be dissipated into space.  Most of that energy then, I believe, is not dissipated in the form of long ether waves, propagated to considerable distance, as is thought most generally, but is consumed—­in the case of an insulated sphere, for example—­in impact and collisional losses—­that is, heat vibrations—­on the surface and in the vicinity of the sphere.  To reduce the dissipation it is necessary to work with a small electric density—­the smaller the higher the frequency.

But since, on the assumption before made, the loss is diminished with the square of the density, and since currents of very high frequencies involve considerable waste when transmitted through conductors, it follows that, on the whole, it is better to employ one wire than two.  Therefore, if motors, lamps, or devices of any kind are perfected, capable of being advantageously operated by currents of extremely high frequency, economical reasons will make it advisable to use only one wire, especially if the distances are great.

When energy is absorbed in a condenser the same behaves as though its capacity were increased.  Absorption always exists more or less, but generally it is small and of no consequence as long as the frequencies are not very great.  In using extremely high frequencies, and, necessarily in such case, also high potentials, the absorption—­or, what is here meant more particularly by this term, the loss of energy due to the presence of a gaseous medium—­is an important factor to be considered, as the energy absorbed in the air condenser may be any fraction of the supplied energy.  This would seem to make it very difficult to tell from the measured or computed capacity of an air condenser its actual capacity or vibration period,