Henley's or Culbertson's Electrometer
   "The electrical charge is roughly measured by the quadrant or Henley's electrometer, which is attached to the conductor. This is a small electric pendulum, consisting of a wooden rod to which is attached an ivory or cardboard scale. In the centre of this is a small whalebone index, movable on an axis, and terminating in a pith ball. Being attached to the conductor, the index diverges as the machine is charged, ceasing to rise when the limit is attained."
From Ganot, Physics (William Wood and Co., New York, 1883) pg 677.

   These four examples are in the Garland Collection of Classic Physics Apparatus at Vanderbilt University, and are unmarked. 

The device was developed by William Henley in 1770; Henley also deveoped the universal discharger.
The small device at the near right is by William Harris of London, and is in the collection at Middlebury College in Vermont. Middlebury was founded in 1800, and the various pieces of Harris apparatus (an Orrery and a Dry Pile) in the collection date from the early years of the college. 

At the far right is an electrometer with the name of B. Pike and Son of New York on it. However, it looks very much like the Harris electrometer at the left; the foot, not shown in the diagram, has the same "brass ferule and pin" for inserting into conductors to indicate their potential. The 1856 catalogue of Benjamin Pike of New York lists this at $1.75 and $2.00 with the ivory scale.

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