Manawatu Herald THURSDAY, JULY 17, 1919. WIRELESS AND THE SUN.

Manawatu Herald, Volume XLI, Issue 2004, 17 July 1919, Page 2

Manawatu Herald THURSDAY, JULY 17, 1919. WIRELESS AND THE SUN.

THE programme of observations arranged in connection with the total eclipse of the snn on May 2!Uh included a series of experiments designed to test the theoretical explanation of the enormous variations in the strength of wireless signals which are observed at sunrise and sunset every day. The experiments were organised by the British Association Committee for Radiotelegraphic Investigation, of which Sir Oliver Lodge is chairman, and comprised the transmission of signals across the zone of the shadow caused by the eclipse. The observers’ results will he collated with a view to finding if the passage of .the shadow cone between a sending and a receiving station causes any regular change in the strength of signal.” According to some writers, the propagation of waves over long distances is greatly affected by the .ionisation of the upper atmosphere. During a solar eclipse the cone of densest shadow removes all sunlight from the atmosphere within it, which may stop the ionising actions exerted by sunlight and allow the recombination of separated ions to take place, fl’his process starts in the penumbra, but it is accomplished fully—or to its fullest extent- —only in the umbra. Thus at any particular fixed place in the air the penumbra, it is thought, first starts gentle recombination of ions, and, as ihe eclipse at The place progresses and darkness, increases, recombination of ions takes place more and more quickly till the time of complete totality; Afterwards the onward passage of the umbra! cone allows sunlight to begin again its. ionising action. Something of this kind is at any rate supposed (o he taking place at sunset and smjinse every day.