RADIUM CLOCKS.

New Zealand Graphic, Volume XXXVI, Issue 23, 9 June 1906, Page 15

RADIUM CLOCKS.

There does not appear to. be any sufficient reason why radium "clocks” should be so called except that they are Calculated to “go” for a long time without - attention. This, in fact, is their most popular feature, and it is calculated tliat these interesting scientific toys contain in themselves sufficient energy to keep them in motion for about two thousand years. 'From a tiny glass tube containing a sinaH-quantrty, of radium two'thin aluminium leaves depend. The negativeiy-olrarged - rays continually, emitted by the precious mineral cause a like charge of electricity to collect upon thq metatttfc' leaves, with the result that they repel one another until one of them torrefies the containing vessel 2 pi*’ looses its chifge. Then the leaves y together, and begin again. With a period-vf .wbout 40 seconds, this process

goes on continuously, and will do so, it is believed, for a score or so of centuries unless the thin metal leaves wear out in the meantime. The little instrument, which, it may be remembered, is the in vention of the Hon. R. J. Strutt, is made by Martindale of London in convenient form for demonstration in the lantern, for which it makes an exceedingly interesting subject.