store. It does release it, as a burn trickles. Slowly the uranium
changes into radium, the radium changes into a gas called the radium
emanation, and that again to what we call radium A, and so the process
goes on, giving out energy at every stage, until at last we reach the
last stage of all, which is, so far as we can tell at present, lead. But
we cannot hasten it.'

'I take ye, man,' whispered the chuckle-headed lad, with his red hands
tightening like a vice upon his knee. 'I take ye, man. Go on! Oh, go
on!'

The professor went on after a little pause. 'Why is the change gradual?'
he asked. 'Why does only a minute fraction of the radium disintegrate
in any particular second? Why does it dole itself out so slowly and
so exactly? Why does not all the uranium change to radium and all
the radium change to the next lowest thing at once? Why this decay by
driblets; why not a decay en masse? . . . Suppose presently we find it
is possible to quicken that decay?'

The chuckle-headed lad nodded rapidly. The wonderful inevitable idea was
coming. He drew his knee up towards his chin and swayed in his seat with
excitement. 'Why not?' he echoed, 'why not?'

The professor lifted his forefinger.

'Given that knowledge,' he said, 'mark what we should be able to do! We
should not only be able to use this uranium and thorium; not only should
we have a source of power so potent that a man might carry in his hand
the energy to light a city for a year, fight a fleet of battleships, or
drive one of our giant liners across the Atlantic; but we should also