Frontispiece to George Adams' An Essay on Electricity ... (2nd Edition, London, 1785)

The illustration above shows a young girl being treated electrically, for pain or paralysis of the forearm. Adams' cylinder generator is at the right, and the main terminal is in the center with a Leyden jar hanging from a metal rod terminated by a metal globe. A metal chain goes from the base of the Leyden jar to a treatment electrode touching the girl's upper arm. The other treatment electrode is connected to a Lane discharging electrometer mounted on the main terminal near the Leyden jar. The electrometer is an adjustable spark gap. Voltage will build up in the main terminal, and the Leyden jar, until the voltage is high enough to leap the gap. Then all the electricity will be carried down the chain to the treatment electrode.

The result will be a powerful shock of electricity applied to the girl's forearm. The size of the shock can be adjusted by the size of the gap the Lane electrometer provides. A shock like this is a powerful stimulus to nerve and muscle. It can deaden pain, or exercise paralyzed muscles for physical therapy. We still do these things today, with more sophisticated equipment -- the TENS (transcutaneous electro-neural stimulation) unit for treatment of pain, and the neuromuscular stimulator for physical therapy.

We have both Adams' book (in several editions) and one of Adams' electrostatic generator kits. This gives the scholar a unique opportunity to compare and contrast the two. A book cannot provide motion and solidity; a device cannot discuss usage and intent. The whole is greater than the sum of the parts.

Cylinder generator by George Adams, London, circa 1785

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© The Bakken Updated: April 6, 2007