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"I carried it a little too far," said Hall, ruefully rubbing the back of his hand, "and when the glass gave way under the atomic bombardment a few atoms of gold visited my bones. But there is no harm done. You observed that the instant the air reached the kathode, as I for convenience call the electrified mass of gold, the action ceased."
"But your anode, to continue your simile," I said, "is constantly exposed to the air." "True," he replied, "but in the first place, of course, this is not really an anode, just as the other is not actually a kathode. As science advances we are compelled, for a time, to use old terms in a new sense until a fresh nomenclature can be invented.
Upon thus charging a metallic body enclosed in a vacuum, I observed that the energy imparted to it possessed the remarkable power of disrupting its atoms and projecting them off in straight lines, very much as occurs with a kathode in a Crookes's tube.
The results which have been obtained in the examination of radio-activity, of kathode rays, of spectra at different temperatures, and of phenomena allied to these, bring again into prominence the ancient problem of the structure of what we call matter. Is matter fundamentally homogeneous or heterogeneous?
When an electric discharge is passed from a plate of metal, arranged as the kathode, to a metallic wire arranged as the anode, both sealed through the walls of a glass tube or bulb from which almost the whole of the air has been extracted, rays proceed from the kathode, in a direction at right angles thereto, and, striking the glass in the neighbourhood of the anode, produce a green phosphorescence.
To attempt "to imagine a model which has in it the potentiality of explaining" radio-activity, the production of kathode rays, and the other chemical and physical properties of elements and compounds, might indeed seem to be a hopeless undertaking. A beginning has been made in the mental construction of such a model by Professor Sir J.J. Thomson.
The tube is exhausted of air, and I am about to concentrate upon the gold an intense electric influence, which will have the effect of making it a kind of kathode pole. I only use this term for the sake of illustration. You will recall that as long ago as the days of Crookes it was known that a kathode in an exhausted tube would project particles, or atoms, of its substance away in straight lines.
Electrons are produced by sending an electric discharge through a glass bulb containing a minute quantity of air or other gas, using metallic plates or wires as kathode and anode. Experiments have shown that the electrons are identical in all their properties, whatever metal is used to form the kathode and anode, and of whatever gas there is a minute quantity in the bulb.
The phenomena of radio-activity, and also the phenomena of the kathode rays, have obliged us to refine our machinery of minute particles by including therein particles at least a thousand times lighter than atoms of hydrogen.
A way of escape was now sought in the reverse direction, by reducing the principles of mechanics to those of electricity, and this especially as confidence in the strict validity of the equations of Newton's mechanics was shaken by the experiments with beta-rays and rapid kathode rays.
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