From this point onward he traces the development of the material astral body as a process of the conversion of the original vibrations into low forms of actual energy which are able to manipulate the atoms of matter and under the directing will of the intelligence or entity build up the materialization. He makes one notable reservation, asserting that “there is no evidence to prove that discarnate intelligence is the directing force. Pure autosuggestion, due to concentrated belief and anticipation that a specified ghost will appear, may achieve the same result.” But the purpose of his paper was not to argue concerning the reality of spirits, but to put forward an ingenious scientific theory concerning their mechanism. The sum-total of his theory is that the physical structure of the hallucination-spirit or ghost-form in its early stages of concentration is destructible by many forms of etheric vibration of greater force or different wave-length. Ghosts and spirits are integrally bound up with the conditions of darkness and dusk. The rays of solar light are admittedly inimical to all these manifestations. In other words, materialization cannot be performed under certain conditions of light which means certain conditions of vibration. The light rays which are visible to the human eye represent about one-tenth of the complete range of light rays known to exist from ultra-violet to infra-red.[17] At other points in the scale of ether waves come the vibrations associated with sound, with electricity and magnetic phenomena and with radioactivity. The complexity of these wave-lengths of vibration is enormous, for within the range of light rays there are rays of another kind of light, so that the sum-total of two kinds of light is, paradoxically enough, darkness.[18] Passing, logically enough, from stage to stage the “Theory of Protective Vibrations” points out that assuming the existence of ghosts or malevolent spirits, these cannot take material shape when opposed by hostile vibrations. Certain kinds of light, sound (such as the sonorous vibrations of church bells or gongs of special note), and high-frequency electric currents all destroy the initial stages of manifestation by purely mechanical means. Lastly he postulates that “in the presence of a radium salt (of specified intensity) ... a ghost cannot manifest.” Protection or exorcism by radium salts is undeniably a twentieth-century possibility, for the terrific and incessant discharge of ether waves consequent upon the disintegration of the radium atoms is so powerful that even such a known and powerful force as electric energy is completely destroyed by it. In the presence of a radium salt non-conductors of electricity become conductors. Differences of potential cease to exist and electroscopes and Leyden jars fail to retain their charges.