He states that if the coherer tube is continuously tapped, say at the rate of fifty vibrations per second, whilst at the same time an increasing potential is applied to its terminals and the current passing through it measured on a galvanometer, there is no abrupt change in current at any point.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming
Secondly, the magnetising current is stopped, and soon after that the secondary coil is unshort-circuited and connected to the galvanometer, and remains in this condition during the remainder of the revolution.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming
An exceedingly small silver ring is suspended by a quartz fibre and has a mirror attached to it in the manner of a galvanometer.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming