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 and the motion of these electrons, under the influence of electrostatic force, must contribute to the electric conductivity of the gas; must, in fact, constitute all of it which was not due to transport of atoms of the gas carrying less than the neutralizing quantum of electrons. Thus every substance must possess radio-activity, said Lord Kelvin. Some interesting remarks would be found in the Philosophical Magazine, where it was pointed out that radium was three hundred million times more active than the most active common material yet experimented with.

How was this enormous radio-activity of radium to be accounted for? Lord Kelvin suggested that it might be because it was exceedingly polyelectronic; that the saturating quantum of electrons in an atom of radium might be hundreds or thousands or millions of times as many as those of atoms of ordinary material. But this left the mystery of radium untouched—Curie's discovery that it perpetually emitted heat at a rate of about 90 Centigrade calories per gramme per hour. If emission of heat at this rate went on for little more than a year, or, say, ten thousand hours, there was as much heat as would raise the temperature of 900,000 grammes of water 1°&ensp;C. It seemed to Lord Kelvin utterly impossible that this