648 Mr. Nihola Tesla [Feb. 4, 



upper coating to one of the terminals of the coil, the discharge 

 appeared in the form of a luminous thread, passing through the axia 

 of the tube. Usually the thread was sharply deliued in the upper 

 part of the tube and lost itself in the lower part. When a magnet 

 or the finger was quickly passed near the upper part of the Imninous 

 thread, it was brought out of position by magnetic or electrostatic 

 influence, and a transversal vibration like that of a suspended cord, 

 with one or more distinct nodes, was set up, which lasted for a few 

 minutes and died gradually out. By suspending to the lower con- 

 denser coating metal plates of different sizes, the speed of the vibration 

 was varied. This vibration would seem to show beyond doubt that 

 the thread possessed rigidity, at least to transversal displacements. ^ 



Many experiments were tried to demonstrate this property in 

 air at ordinary pressure. Though no positive evidence has been 

 obtained, it is thought nevertheless, that a high frequency brush or 

 streamer, if the frequency could be pushed far enough, would be 

 decidedly rigid. A small sj^here might then be moved within it 

 quite freely, but if thrown against it the sphere would rebound. An 

 ordinary flame cannot possess rigidity to a marked degree because 

 the vibration is directionless ; but an electric arc, it is believed, must 

 possess that property more or less. A luminous band excited in a 

 bulb by repeated discharges of a Leyden jar must also possess 

 rigidity, and if deformed and suddenly released should vibrate. 



From like considerations other conclusions of interest may be 

 made. The most probable medium filling the space is one consist- 

 ing of independent carriers immersed in an insulating fluid. If 

 through this medium enormous electrostatic stresses are assumed to 

 act, which vary rapidly in intensity, it would allow the motion of a 

 body through it, yet it would be rigid and elastic, although the 

 fluid itself might be devoid of these properties. Furthermore, on 

 the assumption that the independent carriers are of any configura- 

 tion such that the fluid resistance to motion in one direction is 

 greater than in another, a stress of that nature would cause the 

 carriers to arrange themselves in groups, since they would turn to 

 each other their sides of the greatest electric density, in which 

 position the fluid resistance to approach would be smaller than to 

 receding. If in a medium of the above characteristics a brush would 

 be formed by a steady potential, an exchange of the carriers would 

 go on continually, and there w^ould be less carriers per unit of 

 volume in the brush than in the space at some distance from the 

 electrode, this corresponding to rarefaction. If the potential were 

 rapidly changing, the result would be very different: the higher 

 the frequency of the pulses, the slow^er would be the exchange of 

 the carriers ; finally, the motion of translation through measurable 

 space would cease, and, with a sufficiently high frequency and inten- 

 sity of the stress, the carriers would be drawn towards the electrode, 

 and compression would result. 



An interesting feature of these high frequency currents is that 



