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ANiNUAL REPORT SMITHSONIAN ESTSTITUTION,, 19 42 



May and a minimum in September and October. The curve of this 

 residual annual variation strikingly parallels the annual change in the 

 distribution of ozone in northern latitudes as derived by Dobson. The 

 parallelism of these two curves suggests that possibly the cause of the 

 change in the ozone distribution is intimately associated with that of 

 the changes in the ionosphere resulting in this variation in field 

 strengths. 



Figure 8. — Residual seasonal variation in field strengths of WBBM after correc- 

 tions for twilight effect or angle of depression of the sun below the horizon. 

 The form of the curve is similar to that of the seasonal variation of ozone con- 

 tent of the upper air. 



For the pursuit of these studies in cosmic terrestrial relationships 

 a new laboratory for cosmic terrestrial research has been located in 

 the outskirts of the town of Needham, Mass., where conditions are 

 favorable for radio propagation studies with a minimum of inter- 

 ference, and for observations of atmospheric electric phenomena away 

 from the contamination due to manufacturing in a metropolitan area. 

 The building provides approximately 2,500 square feet of floor space 

 for offices and laboratories. The observational program includes the 

 continuous recording of solar radiation, ultraviolet light, atmospheric 

 potential gradient, ionic content of the lower air and atmospheric 

 electric discharges, as well as the continuation of the measurements of 

 field intensities of radio waves both in the broadcast band and at high 

 frequencies. The relationship of solar observations, ionization phe- 

 nomena at high altitudes, and radio- wave phenomena to the meteor- 

 ology of the lower air affords possibilities for extensive investigations 

 which may become of increasing importance. 



