You will understand that this to-and-fro motion of the electrons in the line-wire varies according to the vibrations of the sending disc, which is controlled by the speaker's voice. At the distant end of the line we electrons bring our magnetic powers into action. We keep varying the attractive powers of an electro-magnet, according to the motion of the electrons in the wire. This ever-changing magnet produces vibrations in an iron disc which is fixed close to the magnet. This disc is set vibrating in exact sympathy with the sending disc. When the listener places this receiving disc close to his ear, the vibrations are carried by the atmospheric atoms to his hearing apparatus. All that we electrons have done is to cause one disc to vibrate in exact synchrony with another distant disc. But that is all that is required, for the receiving disc will reproduce similar air-vibrations to those set up by the man's voice at the distant place. I have pointed out already that we do not attempt to carry the sound. It is true that the atoms of matter do the hard work, but it is we electrons who enable a group of atoms in one town to communicate with a group of atoms in a distant town. It was natural that as soon as man found that he could work his telegraph instruments without the aid of connecting wires, he should try to do the same with his telephone instruments. We were sorry when we found men trying to use the original spark-telegraphy methods for telephones. While we had no difficulty in operating a telegraph instrument by means of æther waves and the tube of filings, it was quite impossible for us to produce telephone vibrations on the same principle. This spark method was a too rough-and-ready plan. The waves we produced were like sudden splashes in the æther ocean, whereas we knew that we must produce regular trains of continuous waves in order to reproduce telephone vibrations. However, you may be aware that we have succeeded by a different arrangement of apparatus. Indeed it may interest you to know that one of my most recent experiences has been in connection with some wireless-telephone experiments. Unfortunately I was not in a very favourable position to learn all that was going on, but it was quite exciting work. I happened to be attached to an atom of copper in a length of wire which had been run up into the air on a sort of flag-pole arrangement. I need hardly say that I was not alone, for by this time you will have become accustomed to picture myriads of electrons occupying a very small space.