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Page:Popular Science Monthly Volume 61.djvu/12

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POPULAR SCIENCE MONTHLY

with negative electricity. He showed by beautiful experiments that this radiant matter bombarded the glass walls and produced phosphorescence, could be focused on to metal sheets and render them red hot, and could drive round little windmills or vanes included in the tube. It therefore possesses the quality of inertia and in virtue of the electric charge it carries, it is virtually an electric current and can be deflected by a magnet. The proof which has been given by Professor Thomson that this 'radiant matter' consists of corpuscles, a thousand times smaller than an atom of hydrogen in mass, and that they are shot off from the kathode with a velocity which is comparable with that of light, explains at once both their kinetic energy and also the manner in which they are able to pass through windows of aluminium, as shown by Lenard, and get into the space outside the tube. Furthermore, evidence has been put forward to show that the electric charge carried by each one of these tiny corpuscles is exactly the same as that which a hydrogen atom carries in the act of electrolysis or when it forms a hydrogen ion.

It seems tolerably clear from all the facts of electrolysis that electricity can only pass through a conducting liquid or electrolyte by being carried on atoms or groups of atoms which are called ions—i. e., wanderers. The quantity thus carried by a hydrogen atom or other monad element, such as sodium, silver or potassium, is a definite natural unit of electricity. The quantity carried by any other atom or group of atoms acting as an ion is always an exact integer multiple of this natural unit. This small indivisible quantity of electricity has been called by Dr. Johnstone Stoney an Electron or atom of electricity. The artificial or conventional unit of electric quantity on the centimeter, gram, second system as defined by the British Association Committee on Electrical Units is as follows:

An electrostatic unit of electric quantity is the charge which when placed upon a very small sphere repels another similarly charged sphere, the centers being one centimeter apart, with a mechanical force of one dyne. The dyne is a mechanical unit of force and is that force which acting for one second on a mass of one gram gives it a velocity of one centimeter per second. Hence, by the law of inverse squares the force in dynes exerted by two equal charges at a distance is equal to . Two other units of electric quantity are in use. The electromagnetic unit, which is thirty thousand million times as great as the electrostatic unit, and the practical unit called the coulomb or ampère-second which is three thousand million times the electrostatic unit. We can calculate easily the relation between the electron and the coulomb; that is, between nature's unit of electricity and the British Association unit, as follows:

If we electrolyze any electrolyte, say acidified water which yields