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few trees located on or about the reflection area corresponding to the 

 higher antenna positions. The result is particularly noticeable for the 

 vertically polarized transmission where the fit between observation 

 and experiment is poor. This experiment was later repeated with the 

 same results. The conclusion follows that while the oscillatory charac- 

 ter of the field intensity curves indicates a definite local reflection com- 

 ponent, it is not as simple as the one arising from a smooth surface 

 by plane optical reflection. 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 160 

 MILES FROM TRANSMITTER 



Fig. 16 — Flight toward transmitter. Altitude — 8000 feet; 

 wave-length — 4.3 meters, June 24, 1931. 



The middle distance reflection was clearly established by airplane 

 observations. For these only vertically polarized radiation was used, 

 and a simple vertical rod antenna was thrust out of the airplane cabin 

 ceiling. This limited the maximum range which was attained, but an- 

 tennas of greater effective height were difficult to construct. This 

 plane was the Laboratories' Ford trimotor, and we are indebted to Mr. 

 F. M. Ryan and his staff for their cooperation in this work. The 

 manual recorder already mentioned was used throughout the runs, 

 which were made by flying directly from Beer's Hill to Easton, Pa., and 



