Crookes had hoped that the scientists of his day would be positively interested in his researches. But his first paper in this field, 'On Phenomena called Spiritual', was at once and almost unanimously rejected by his colleagues, and as long as he concerned himself with such matters he suffered through their opposition. It passed his understanding as a scientist why anything should be regarded in advance as outside the scope of scientific research. After several years of fruitless struggle he broke off his investigations into spiritism, deeply disillusioned at his failure to interest official science in it. His own partiality for it continued, however (he served as President of the Society for Psychical Research from 1896-9), and he missed no opportunity of confessing himself a pioneer in the search for the boundary-land between the worlds of matter and spirit. Through all his varied scientific work the longing persisted to know more of this land.
Just as Crookes had once sought to investigate spiritism scientifically, so in his subsequent scientific inquiries he was always something of a spiritist. He admitted, indeed, that he felt specially attracted by the strange light effects arising when electricity passes through rarefied gases, because they reminded him of certain luminous phenomena he had observed during his spiritistic investigations. Besides this, there was the fact that light here showed itself susceptible to the magnetic force in a way otherwise characteristic only of certain material substances. Accordingly, everything combined to suggest to Crookes that here, if anywhere, he was at the boundary between the physical and the superphysical worlds. No wonder that he threw himself into the study of these phenomena with enthusiasm.
He soon succeeded in evoking striking effects - light and heat, and also mechanical - along the path of electricity passing invisibly through the tube later named after him. Thus he proved for the first time visibly, so to say, the double nature - material and supermaterial - of electricity. What Crookes himself thought about these discoveries in the realm of the cathode rays we may judge from the title, 'Radiant Matter', or 'The Fourth State of Matter', which he gave to his first publication about them. And so he was only being consistent when, in his lectures before the Royal Institution in London, and the British Association in Sheffield in 1879, after showing to an amazed scientific audience the newly discovered properties of electricity, he came to the climax of his exposition by saying: 'We have seen that in some of its properties Radiant Matter is as material as this table, whilst in other properties it almost assumes the character of Radiant Energy. We have actually touched here the borderland where Matter and Force seem to merge into one another, the shadowy realm between Known and Unknown, which for me has always had peculiar temptations.' And in boldly prophetic words, which time has partly justified, he added, 'I venture to think that the greatest scientific problems of the future will find their solution in this Borderland, and even beyond; here, it seems to me, lie Ultimate Realities, subtle, far-reaching, wonderful.'
No one can read these words of Crookes without hearing again, as an undertone, the question which had forced itself on him at the bedside of his dead brother, long before. All that is left of the human being whom death has taken is a heap of substances, deserted by the force which had used them as the instrument of its own activity. Whither vanishes this force when it leaves the body, and is there any possibility of its revealing itself even without occupying such a body?
Stirred by this question, the young Crookes set out to find a world of forces which differ from the usual mechanical ones exercised by matter on matter, in that they are autonomous, superior to matter in its inert conglomeration, yet capable of using matter, just as the soul makes use of the body so long as it dwells within it. His aim was to secure proof that such forces exist, or, at any rate, to penetrate into the realm where the transition from matter to pure, matter-free force takes place. And once again, as in Galvani's day, electricity fascinated the eyes of a man who was seeking for the land of the soul. What spiritism denied, electricity seemed to grant.
The aversion to spiritism which Crookes met with in contemporary science was, from the standpoint of such a science, largely justified. Science, in the form in which Crookes himself conceived it, took for granted that the relationship of human consciousness to the world was that of external onlooking. Accordingly, if the scientist remained within the limits thus prescribed for consciousness, it was only consistent to refuse to make anything beyond these limits an object of scientific research.
On the other hand, it says much for the courage and open mindedness of Crookes that he refused to be held back from what was for him the only possible way of extending the boundaries of science beyond the given physical world. Moreover, it was only natural that in his search for a world of a higher order than the physical he should, as a man of his time, first turn his attention to spiritistic occurrences, for spiritism, as it had come over to Europe from America in the middle of the nineteenth century, was nothing but an attempt by the onlooker-consciousness to learn something in its own way about the supersensible world. The spiritist expects the spirit to reveal itself in outwardly perceptible phenomena as if it were part of the physical world. Towards the end of his life Crookes confessed that if he were able to begin again he would prefer to study telepathic phenomena - the direct transference of thought from one person to another - rather than the purely mechanical, or so-called telekinetic, expressions of psychic forces. But although his interest was thus turning towards a more interior field of psychic investigation, he remained true to his times in still assuming that knowledge about the world, whatever it might be, could be won only by placing oneself as a mere onlooker outside the object of research.
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The stream of new discoveries which followed Crookes's work justified his conviction that in cathode ray phenomena we have to do with a frontier region of physical nature. Still, the land that lies on the other side of this frontier is not the one Crookes had been looking for throughout his life. For, instead of finding the way into the land whither man's soul disappears at death, Crookes had inadvertently crossed the border into another land - a land which the twentieth-century scientist is impelled to call 'the country that is not ours'.
The realm thrown open to science by Crookes's observations, which human knowledge now entered as if taking it by storm, was that of the radioactive processes of the mineral stratum of the earth. Many new and surprising properties of electricity were discovered there - yet the riddle of electricity itself, instead of coming nearer, withdrew into ever deeper obscurity.