WIRELESS TELEPHONY — FESSENDEN. 



191 



thought to increase continuously with the wave length." This fluc- 

 tuating absorption at one time appeared to place a fundamental 

 obstacle to commercial wireless telegraphy, as telegraph engineers 

 will easily appreciate the impossibility of operating telegraph sys- 

 tems with circuits where the strength of the received signals may fall 

 to one thousandth of its value or rise to a thousand times its value 

 in the course of a few minutes. 



DAY OF MONTH 

 Fig. 7. — Curve showing variation of intensity of transatlantic messages for tlie month 



of January, 1900. 



It was therefore considered absolutely essential, in order to decide 

 whether long-distance wireless telegraphy was commercially^ possible 

 or not, to investigate this phenomenon fully. As a preliminary, the 

 station at Brant Rock sent signals to four or five other stations at 

 varying distances and comparative readings were taken. The follow- 

 ing table shows the general character of the results obtained : 



Company's cottage 



Lynn 



Schenectady 



Philadelphia 



Washington 



Machrihanish 



" Strength of unabsorbed signals taken as 1,000. 



These experiments proved conclusively that the absorption did 

 not take place in the neighborhood of the sending station, because 



<^ A mathematical explanation of this supposed fact was given by Doctor 

 Fleming, Principles of Electric Waves Telegraphy, pp. 617-61S, 190G, the follow- 

 ing conclusions being reached : 



" Accordingly, the chief part of the weakening of the wave by sunlight is 

 done In the neighborhood of the sending antenna, where the magnetic force H 

 is greatest, and it is more sensible for long and powerful waves than for short 

 and feeble ones. This agrees with the observations of Mr. Marconi." 



