92 PHYSICS OF MATTER 



The problems of the present which have aroused general interest 

 are those which pertain to the physical constitution of matter. And 

 here we are at once confronted with the question, What do we mean 

 by matter? How is matter to be recognized? Of late we have been 

 hearing such phrases as "the electrical theory of matter." There 

 seems to be a marked tendency towards the idea that matter and its 

 properties are alike electrical phenomena. Some even intimate that 

 the molecular theory of gases, and the atomic theory of the chemist 

 are tottering to a fall. We have long known that matter in motion 

 is a form of energy. This energy of moving matter is continually 

 being converted into molecular or atomic vibration, and then escapes 

 from us, apparently, forever, in the form of ether waves. We have 

 also long known that electricity in motion is a form of energy, and 

 that the energy so manifesting itself is also all finally converted into 

 heat, and then into ether waves. 



Now this parallel certainty suggests an electrical theory of matter, 

 but it also suggests, equally, a material theory of electricity. And so 

 far from being antagonistic, these two theories are identical. There 

 is nothing whatever to show that electricity has ever been separated 

 from something which has what we have been accustomed to call 

 mass. Rowland 1 found that when the charged sectors on his rotating 

 disk were rotated, a magnetic field was produced, corresponding 

 to that produced by a current of electricity. If the motion of the 

 matter which carries the positive electric charge is in a positive direc- 

 tion, the field is the same as that produced when a negative charge 

 is moved in a negative direction. 



Rutherford has recently found phenomena of radioactive matter 

 which have a most vital interest in connection with Rowland's work. 

 The a and /? particles which are shot off from such matter are mov- 

 ing in the same direction, and they are oppositely deflected in a mag- 

 netic field. They behave like superposed or perhaps juxtaposed 

 electric currents of opposite sign flowing in the same direction. If 

 in these radiations the a and /? particles were moving in opposite 

 directions, then in a magnetic field they would be deflected in the 

 same direction. This at once raises a question concerning the nature 

 of an electric current in a conducting wire. Let us assume that we 

 start with the positive and negative charges on the terminals of the 

 Holtz machine. What is it that is taking place when the terminals 

 are joined by wires leading to a galvanometer? We get a current 

 which we are wont to say is due either to a positive current flowing 

 in a positive direction, or to a negative current flowing in an opposite 

 direction. If we cease to apply work to the rotating wheel, it comes 

 to rest, and the potential of the conducting wire becomes uniform 

 throughout. Its extremities which terminate in front of the charged 

 1 American Journal of Science, [3] xv, 30-38, 1878. 



