In fact, it requires about double the voltage to force a spark of the same length through air compressed at 50lb.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming
This electromotive force varies as the length of the receiving aerial and as the magnetic force due to the wave cutting across it, and the magnetic force varies as the current in the transmitting aerial, and therefore, for any given voltage varies as the capacity, and therefore as the length of the transmitting aerial.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming
He ascertained that there was a complete correspondence between the sensitiveness of the tubes used as telegraphic instruments and the form of the characteristic curve of current and voltage drawn by the above-described method.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming