voltaic or slide inductor
My grandfather built this wonderful piece of equipment.
It takes a single D size battery and transforms the 1.5 Volt battery current to an alternating voltage that one can feel when you let it pass through one's body!
As a child I can recall enjoying the tingling sensation of the current and watching and feeling how the muscles contract as one increases the current. From playing with this device my own children now understand how electricity must complete a circuit in order for it to flow and how wetting a dry contact improves the flow!
The only other references I have found to such devices are from Siemens. I saw a similar device on display at the Siemens Museum in Munich. The accompanying text described it as follows:
The voltaic inductor consists of a magnetic hammer brake and a high-voltage transformer with sliding second coil to adjust current and voltage. It was used for galvanic baths and it was the first electro-medical equipment made by Siemens & Halske
The story goes that Emil du Bois-Reymond and Werner Siemens improved the inductor by adding a secondary winding and a slider that altered the magnitude of it's effect. They presented the new version to the Berlin Physiological Society on 16 May 1848. The improved inductor was later named after du Bois-Reymond and Siemens presented a larger version at the International Exhibition in London In 1862.
It was developed in the hope that electrical current was medically beneficial and was used primarily in galvanic baths. Later it was used to power the first X-Ray devices.