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One of Crookes's appliances of 1879, showing the propulsion of a wheel by the impact of the cathode rays when they are deflected by a horseshoe magnet so as to impinge on its vanes.
of as now only recognizing the transmutation of some preexisting complex atoms into simpler forms. The evolution of matter was glimpsed as a brilliant dream by Sir W. Crookes, when he presided over the Chemical Section of the British Association in Birmingham in 1886: he may yet live to see his dream come true.
The family relationship between the atomic weights of the elements, described by Mendelejeff and others, paved the way for and suggested the vision: scientific progress ever since has brought it nearer to realization; and the splendid mathematical theories of J. J. Thomson and Larmor, concerning the properties and powers of electric charges, have now rendered possible a far greater precision of imagination than was then possible, and have engendered the conception of an atom of matter composed wholly of electricity:—which thus steps on to the stage as the fundamental and really atomic substance.
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A Crookes tube showing a mineral held up to the bombardment of cathode rays, from the negative terminal above, in a highly exhausted vacuum globe.
The Physical basis of life still eludes us; and until we are willing to look outside our material environment into another order of things, the full truth concerning life and mind will I believe continue to be unrecognizable. But let us always remember that both life and mind have a physical basis, a complete material aspect: it may be possible for the mechanism of this aspect to be dragged to the light of day and displayed, perhaps as clearly and definitely as we hope before long to be able to display the constitution of matter itself. Let not the reader of this article assume that it represents more than the gropings of a searcher after knowledge, illuminated by the light of his brethren, trained quickly to seize and understand, and trying to act as an instructed guide or interpreter amid the haze; though he recognizes, and would have others recognize, that the haze has not yet lifted, and that accordingly his statements must be understood as nothing more than an approximation to the truth.
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A Crookes tube (1879) showing a piece of platinum made red hot by the concentrated impact of the cathode rays from a bowl-shaped negative terminal inside a vacuum globe not too highly exhausted. If the exhaustion is carried further, the platinum does not get so hot, but emits X-rays, as discovered by Roentgen, Porter, and Jackson (1885).
| Crookes, Cathode Rays | 1879 |
| Roentgen, X-rays | 1895 |
| Becquerel, Radioactivity | 1896 |
| Madame Curie, Radium | 1898 |
| Curie, Heat-production | 1903 |
| Larmor, Electrons | 1895 |
| J. J. Thomson, Electrons | 1899 |
| Rutherford, Disintegration | 1903 |
