6 POPULAR SCIENCE MONTHLY. 



with negative electricity. He showed by beautiful experiments that 

 this radiant matter bombarded the glass walls and produced phosphor- 

 escence, 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. Further- 

 more, 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 elec- 

 tricity 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 centi- 

 meter, 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 Q at a distance 

 D is equal to Q 2 /D 2 . 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 ampere-second which is three thousand million times the electro- 

 static 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 



