Johnson's natural philosophy and key to philosophical charts : illustrated with 500 cuts; being reduced photographic copies of all the diagrams contained in the author's philosophical series of indestructible school charts ; for the use of schools and families (1878)
ith exactly the same quantity of electricity. 664 Proof-plane.—riie proof-planeis an instrument for determining the rela-tive quantities of electricity that are foundon the different parts of an electrified conductor. It consists of a diskof gilt paper, attached to the end of an insulating rod, as…
Physics · Astronomy
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