1007.] on Recent Contributioas to Electric Wave Telegraphy. 709 



communication between ship und ship, or ship and shore, over un- 

 usually large distances. Ships equipped with what is called short- 

 distance apparatus, that is intended to send and receive over 200 miles 

 or so, are able occasionally to communicate with others 600, 800, or 

 even IdOO miles away. This is not altogether a matter of personal 

 skdl or of apjiaratus. Our terrestrial atmosphere varies from day to 

 day and hour to hour in its transparency to long telegraphic electric 

 waves, just as it does to the short light waves. One reason, and probably 

 a valid one, which has been advanced for this is the ionisation of the 

 atmos[)here by sunlight, radio-active matter, or matter electrically 

 charged reaching our earth from the sun or cosmical space. These 

 ions or electrically charged particles suspended in the air are set in 

 motion by the electric force of long electric waves passing through 



4\ 



Fig. 22. 

 Polar Diagram for Braun's Triple Directive Antenna. 



the region. This, however, involves energy which must be taken 

 from the wave, and hence the wave passes on so much the weaker. 

 This effect is altogether different from the disturbing effects of atmo- 

 spheric electricity on the receiving antenna. As first noticed by Mr. 

 Marconi on one of his Atlantic voyages, the atmospheric transparency 

 for long electric waves is decreased by dayhght and this reducing 

 effect of light on the wave energy takes place chiefly near the trans'^ 

 mittmg antenna where the electric force is largest. It fluctuates from 

 hour to hour and month to month according to laws as yet undeter- 

 mined, and has no doubt secular and irregular fluctuations superposed 

 on its regular variations. The subject" of long distance wireless 

 telegraphy is yet too young to provide observations for any safe 



