2. A bundle of fine iron wires embedded in paraffin.
3-9. Six cylinders of the agglomerate of
chemically-reduced iron in powder and paraffin,
containing respectively 5, 10, 15, 20, 25 and 50 per
cent. of iron.
Signalling across space without wires being a description of the work of Hertz & his successors · 第 34 / 35 题