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BELL SYSTEM TECHNICAL JOURNAL 



plotted in Fig. 18 with the calculated boundary heights set down at 

 the right hand, spread out in time of observation. The boundary 

 height coincidence is pretty definitely located in this manner. Many 

 of the more complicated frequency sweep patterns carried a fine struc- 



JUNE 23, 1936 



JUNE 27, 1936 



JUNE 29, 1936 



-10 10 20 500 600 700 530 



TEMP IN ° C DIELECTRIC CONSTANT 



2 6 10 14 18 

 VAPOR PRESSURE 

 MILLIBARS Pyy 



600 630 700 



AM EASTERN STANDARD TIME 



Fig. 18 — Comparison of boundary heights shown by the U. S. Weather Bureau 

 free air data, with boundary heights measured from frequency sweep patterns. 

 Horizontally polarized transmission. 



