To complete the picture which I was drawing, you have only to think of the æther waves arriving upon this planet and disturbing sympathetic electrons, causing them to revolve around their atoms in similar fashion to our distant fellows who are producing the æther waves. It may be that some people get confused between this action and that of those electrons who are shot off bodily from the sun towards the earth. Believe me, there is no connection between the two things. The stream of electrons shot off from the sun is deflected towards the magnetic poles of the earth, and as the electrons enter the upper layers of the atmosphere they produce that beautiful luminous effect which man describes as an _Aurora_. I have never taken part in one of these great displays, for, as far as my recollection goes, I have never been in the sun, although some fellow-electrons declare that at one time we were all in the same great glowing mass of which the sun, and every member of the solar system, formed a part. However that may be, I certainly have no experience of auroræ, but I have assisted in producing the very same effect upon a small scale within a vacuum tube. The air remaining in these so-called vacuum tubes is just as rarified as the air in the upper layers of the atmosphere, and when we are shot across the tube we act in the same way as those electrons arriving upon this planet from the sun. You will observe that as a surplus of electrons arrives upon the earth from the sun, the earth is naturally a negatively electrified body, but I need hardly say that the earth does not keep all the electrons which arrive upon it. My scribe points out that I am wandering from the story which I set out to tell in this chapter, so I shall try and please him. The direct cause of light, whether it be natural or artificial, is the rapid motion of electrons around atoms of matter. If they revolve at a comparatively slow speed they produce those æther waves which man calls _radiant heat_. If these satellite electrons, however, desire to affect the eye of man, they have to move around at a very much greater speed. If we travel at too fast a speed, then we cease to cause the sensation of light. But, believe me, all the waves we make are of the same nature, no matter what names man has given them. The only difference we can make in the waves is the rate at which they follow one another. Of course we can also make them larger or smaller in height, or, in other words, of greater or less amplitude, but that does not affect their properties. In the following chapter I shall tell you of some remarkable phenomena which our different æther waves produce in the brain of man. CHAPTER XIV HOW WE PRODUCE COLOUR _THE SCRIBE'S NOTE ON CHAPTER FOURTEEN_ Colour is merely a sensation in the brain. What the electrons really produce are æther waves, and these give rise to the sensations of colour.