APPENDIX.
THE ÆTHER OF SPACE.
Much discussion has taken place, especially between physicists and chemists, over the nature of the substances with which all space must, according to scientific hypothesis, be filled. One side contends that it is infinitely thinner than the thinnest gas, absolutely frictionless and without weight; the other asserts that it is denser than the densest solid. In this substance the ultimate atoms of matter are thought to float, like motes in a sunbeam, and light, heat and electricity are supposed to be its vibrations.
Theosophical investigators, using methods not at the disposal of physical science, have found that this hypothesis includes under one head two entirely different and widely separated sets of phenomena. They have been able to deal with states of matter higher than the gaseous and have observed that it is by means of vibrations of this finer matter that light, heat and electricity manifest themselves to us. Seeing that matter in these higher states thus performs the functions attributed to the ether of science, they have (perhaps unadvisedly) called these states etheric, and have thus left themselves without a convenient name for that substance which fulfils the other part of the scientific requirements.
Let us for the moment name this substance koilon, since it fills what we are in the habit of calling empty space. What mûlaprakrti, or "mother-matter," is to the inconceivable totality of universes, koilon is to our particular universe—not to our solar system merely but to the vast unit which includes all visible suns. Between koilon and mûlaprakrti there must be various stages, but we have at present no direct means of estimating their number or of knowing anything whatever about them.