326 



AUSTIN: SIGNALS IN RADIOTELEGRAPHY 



the probability of overlapping is 0.12, of triple overlapping of 

 grains is 0.008. Tabulating for ten layers, 



TABLE II 



The second and third columns give respectively the transparency 

 and absorption of the first n layers. The fourth column gives the 

 increment of absorption due to the nth layer. The fifth column 

 gives the probability of n grains overlapping in n layers. The 

 last column gives the probability of n grains being in line in all 

 ten layers, it is A- 10! / N! (10-?i)! 



RADIOTELEGRAPHY. — Difference in strength of day and night 

 signals in radiotelegraphy . L. W. Austin, U. S. Naval Radio- 

 telegraphic Laboratory. 



The first explanation, given of the difference in strength of day 

 and night signals after the discovery of the phenomenon by Mar- 

 coni, was that sunlight, by ionizing the air around the sending 

 antenna, produced energy losses which resulted in a decrease in 

 the strength of the received signals. This idea has long been 

 abandoned as affording a full explanation of the phenomenon. 

 Recent observations between the Arlington station and the sta- 

 tion at the Bureau of Standards, 8 kilometers apart, show that 

 if the effect exists at all it is a matter of not more than 1 or 2 

 per cent. 



At a later period it was supposed by many workers in radio- 



