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The minute particles of two of the substances for many years classed as elements give off electrons; uranium and thorium are radio-active. Electrons are produced by sending an electric discharge through very small traces of different gases, using electrodes of different metals.
Recently this subject has been taken up afresh, with a result which may be stated roughly in the following terms: If the sixty-five or sixty-eight recognised 'elements' are arranged in the order of their atomic weights from hydrogen, the lightest, as unity, to uranium, the heaviest, as 240 the series does not exhibit one continuous progressive modification in the physical and chemical characters of its several terms, but breaks up into a number of sections, in each of which the several terms present analogies with the corresponding terms of the other series.
Through four successive skins of inoson, the theoretical ultimate of possible strength, toughness, and resistance, that frightful beam drove before the automatically-reacting detector closed the slit and the impregnable defensive screens, driven by their mighty uranium bars, flared into incandescent defense.
Studying the action of the salts of a rare and very heavy mineral called uranium Becquerel observed that their substances give off an invisible radiation which, like the Roentgen rays, traverse metals and other bodies opaque to light, as well as glass and other transparent substances. Like most of the great discoveries it was the result of accident.
It is the number of positive particles of electricity an atom has that determines the kind of an element that is formed when enough atoms of the same kind are joined together to build it up. Thus hydrogen, which is the lightest known element, has one positive particle for its nucleus, while uranium, the heaviest element now known, has 92 positive particles.
He was out here poking around in my fields and up in the hills from dawn till dark. Said he was making some soil tests. I yelled at him for stepping all over some baby fruit trees." "That's it, then," said Roger grimly. "This area is jumping with uranium and Vidac now has title to the land!" "Don't be so sure," said Tom. "We still need proof."
The exposure to sunlight which had been regarded as essential to the success of the former experiments had really nothing at all to do with the matter, the essential thing was the presence of uranium and the photographic effects were not due to X-rays but to the rays or emanations which Becquerel had thus discovered and which bear his name.
For two blocks on either side of the street, in building after building, cafés, pawnshops, cheap restaurants above and below the street level, supplied the needs of countless shadowy figures who came and went as silently as ghosts. Spaceman's Row was where suspended spacemen and space rats, prospectors of the asteroids for uranium and pitchblende, gathered and found short-lived and rowdy fun.
Inasmuch as all minerals which contain compounds of uranium contain compounds of radium also, it is probable that radium is one of the disintegration-products of uranium. The rate of decay of radium may be roughly expressed by saying that, if a quantity of radium were kept for ten thousand years, only about one per cent. of the original quantity would then remain unchanged.
Uranium, the supposed basis of the latest discovery, Radium, has only one-millionth part of the heat of the latter. The slow-moving earth takes twenty-four hours to turn upon its axis. Radium covers an equal distance while we pronounce its name. One and one-quarter seconds, and twenty-five thousand miles are traversed. Puck promises to put his "girdle round the earth in forty minutes."
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