Hand with Proof-plane

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“A proof-plane may be made by cementing a bronze cent or a disk of gilt paper to a thin insulating handle, as a glass tube or a vulcanite rod. Slide the disk of the proof-plane along the surface of the electrified body to be tested, and quickly bring it into contact with the knob of the gold-leaf electroscope, the leaves of which will diverge.” — Avery, 1895


hand, plane, rod, test, proof


Elroy M. Avery School Physics (New York: Sheldon and Company, 1895) 417


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