men frequency and man potential currents. 133

as it, allows energy to be dissipated by molecular impact or bom-bardment. The action is tlms explained:—When an insulatedbody connected to a terminal of the coil is suddenly charged tohigh potential, it acts inductively upon the surrounding air, orwhatever gaseous medium there might be. The molecules oratoms which are near it are, of course, more attracted, and movethrough a greater distance than the further' ones. When thenearest molecules strike the body the}' are repelled, and collisionsoccur at all distances within the inductive distance. It is nowclear that, if the potential be steady, but little loss of energy canbe caused in this way, for the molecules which are nearest tothe body having had an additional charge imparted to them bycontact, are not attracted until they have parted, if not with all,at least with most of the additional charge, which can be accom-plished only after a great many collisions. This is inferred fromthe fact that with a steady potential there is but little loss in dryair. When the potential, instead of being steady, is alternating,the conditions are entirely different. In this case a rhythmicalbombardment occurs, no matter whether the molecules aftercoming in contact with the body lose the imparted charge ornot, and, what is more, if the charge is not lost, the impacts areall the more violent. Still, if the frequency of the impulsesbe very small, the loss caused by the impacts and collisions wouldnot be serious unless the potential was excessive. But whenextremely high frequencies and more or less high potentials areused, the loss may be very great. The total energy lost per unitof time is proportionate to the product of the number of impactsper second, or the frequency and the energy lost in each impact.But the energy of an impact must be proportionate to the squareof the electric density of the body, on the assumption that thecharge imparted to the molecule is proportionate to that density.Tt, is concluded from this that the total energy lost must be pro-portionate to the product of the frequency and the square of theelectric density; but this law' needs experimental confirmation.Assuming the preceding considerations to be true, then, by ra-pidly alternating the potential of a body immersed in an insulat-ing gaseous medium, any amount of energy may be dissipatedinto space. Most of that energy, then, is not dissipated in theform of long ether waves, propagated to considerable distance,as is thought most generally, but is consumed in impact andcollisional losses—that is, heat vibrations—on the surface and in