The ground battery

[Esteban]

Similar process occurs with good conductive metals buried for long time. You need high Z earphones. This is very sensitive. If you touch connections of it and put near a 50 Hz iron solder, you'll hear the 50 (or 60 Hz)... near a 50% of a LM386 level, for example, BUT WITHOUT BATTERY.

PM, March 1906.

[Esteban]

Now if you wet two fingers with water or spittle (maybe is enough transpiration), and quickly touch the plug contacts of these old headphones, you hear a very low click, without having to be near a source of interference such as 50 Hz, for example.

[Esteban]

No need to be closed the circuit of the battery in this example. Note that the copper plates are separated by rubber... PM, July 1907.

[Max]

Plain pathetic

[Esteban]

In few words, the matter is how can see the things from another angle, not from a short perspective.

[Max]

from the pathetic perspective maybe