Hence along a line drawn perpendicular to the radiator through its centre, there is a distribution of electric strain normal to that line, which is periodic in space and in time.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming
If we arrange matters so that the impulses communicated to the bottom end of the long spiral wire correspond to its fundamental note or periodic time, then in a darkened room we shall see a luminous glow or discharge between the vertical wire and the spiral wire, which increases in intensity all the way up to the top of the spiral wire.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming
The periodic flares continued to come throughout the long night, as if now no longer pleading for acknowledgment, but rather reassuring men in such deep distress that they could not answer.
"Eight Keys to Eden"
Mark Irvin Clifton