The two sets of figures show some corroborative features, notably the low frequency from 1860 to 1870.
When fitted with a spark gap the high voltage, low frequency currents are converted into high voltage, high frequency currents.
Such an experiment can be performed also with low frequency currents, but much less satisfactorily.
When produced with currents of low frequency, obtained from a coil operated as usual, this thread is inert.
I pass a steady or low frequency current through the wire, and it is heated uniformly in all parts.