Answer: Hermann von Hemholtz believed that since electricity cast a shadow, arcs of electricity must be made of tiny, tiny, TINY particles: electrical atoms; or electrons.
Explanation: a scientist by the name of J.J. Thomson conducted an experiment to test the velocity of electricity, predicting it to be as fast as light. but it was actually much slower than light, which could only mean that it had mass; which means the electron is a form of matter.