I04 



POPULAR SCIENCE MONTHLY. 



Inside the rods we have a movement of electrons and co-electrons to 

 and fro, electric charges at the ends of the rods alternating with elec- 

 tric currents in the rods, the charges being at a maximum when the 

 current is zero, and the current at a maximum when the charges have 

 for the moment disappeared. Outside the rods we have a correspond- 

 ing set of charges, lines of electric strain stretching from end to end 

 of the rod, alternating with rings of magnetic flux embracing the rod. 

 So far we have supposed the oscillation to be relatively a slow one. 



Imagine next that the to and fro movement of the electrons or 

 charges is sufficiently rapid to bring into play the inertia quality of the 

 medium. We then have a different state of affairs. The lines of 

 strain in the external medium can not contract or collapse quickly 



Fig. 2. Successive Stages in the Defoemation of a Line of Strain between Posi- 

 tive AND Negative Electbons in Rapid Oscillation, showing Closed Loop of Electbic 

 Stbain thbown off. 



enough to keep up with the course of events, or movements of the elec- 

 trons in the rods, and hence their regular contraction and absorption is 

 changed into a process of a different kind. As the electrons and co- 

 electrons, i. e., the electric charges, vibrate to and fro, the lines of 

 electric strain connecting them are nipped in and thrown off as com- 

 pletely independent and closed lines of electric strain, and at each 

 successive alternation, groups or batches of these loops of strain are 

 detached from the rod, and, so to speak, take on an independent exist- 

 ence. The whole process of the formation of these self-closed lines of 

 electric strain is best understood by examining a series of diagrams 

 which roughly represent the various stages of the process. In Fig. 2 

 we have a diagram (a) the curved line in which delineates approxi- 



