[8] NOTE.--A writer in the _New Science Review_ undertakes to answer the question: “What is electricity?” In order to lead the reader up to the main question, he first considers the natural forces, gravitation and heat. Examples are given of how these forces are manifested and how energy is changed from one form to another. Every form of force, the author says, should be regarded as a different method in which energy makes itself known to the senses. He calls particular attention to the important fact that the “resistance of one kind or another is always the agent that acts to alter energy from one form to another,” and suggests that electricity is simply a form or manifestation that energy may assume under given conditions, and generally is a mere transitory stage between the mechanical form and the heat form. “In most operations,” he continues, “mechanical force passes to the heat form without passing through the electric form; but whenever magnetism is brought into play as a resistance that must be overcome, then mechanical power applied to overcome this resistance always becomes electricity, if only momentarily in its passage from the mechanical to the heat form.” In conclusion, he asks if the question: “What is electricity?” cannot be answered in a fairly satisfactory way by saying that it is simply a form that energy may assume while undergoing transformation from the mechanical or the chemical form to the heat form or the reverse. [9] NOTE.--The cathode is the conductor by which current flows away as distinguished from the _anode_ or conductor through which the current enters. The terms usually apply to conductors leading the current through a liquid or gas, as an electrolytic cell, or vacuum tube. [10] NOTE.--The name _voltameter_ was given by Faraday to an electrolytic cell employed as a means of measuring an electric current by the amount of chemical decomposition the current effects in passing through the cell. [11] NOTE.--Faraday’s own description of his discovery is as follows: “Two hundred and three feet of copper wire in one length were coiled round a large block of wood; another two hundred and three feet of similar wire were introposed as a spiral between the turns of the first coil, and metallic contact everywhere prevented by twine. One of these helices was connected with a galvanometer, and the other with a battery of one hundred pairs of plates, four inches square, with double coppers, and well charged. When the contact was made there was a sudden and very slight effect at the galvanometer, and there was also a similar slight effect when the contact with the battery was broken.” [12] NOTE.--In reality it would be impossible to have a magnetic field exactly like fig. 129, for in the less dense part, the magnetic lines would be of curved complex form. [13] NOTE.--These values are correct for effective sinusoidal voltages.