All other things being equal, the more voltage you have, the farther a spark can jump. That's the idea behind the discharging electrometer invented by Timothy Lane in 1767. You can adjust a spark gap (from B to C in the illustration above). As the Leyden Jar accumulates charge from the electrostatic generator, its voltage will rise. It will keep rising until there is enough voltage to jump from B to C. Then all the charge in the Leyden Jar will jump the gap and be sent through the patient, in this illustration from the electrodes at elbow and wrist,

Physicians experimenting with electrical treatments could thus standardize what they were doing. They would speak of "a discharge of one inch from a Leyden Jar of one gallon capacity" and another physician would be able to apply roughly the same treatment. While the capacity of Leyden Jars of the same size would not necessarily be the same, it would be in the same ballpark. Another use of the discharging electrometer is shown in Adams' work.

The Bakken has many discharging electrometers, which usually came as part of a set of electrical apparatus. An illustration rather than a photograph was chosen to better represent the usage of the device.

Museum Hours: Tuesday - Saturday 10 to 5
Thursdays 10 am to  8pm 
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© The Bakken Updated: April 6, 2007