164 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



Chapman has shown that if there is a corpuscular emanation from 

 the sun affecting the ionosphere and if these corpuscles travel, as 

 would be surmised, at velocities much slower than those of light, the 

 effect of the moon in screening off from the earth such a stream of 

 charged particles should cause disturbances in the ionosphere as much 

 as 2 hours in advance of the optical shadow. Such an effect was looked 

 for in the case of the New England eclipse of 1932 but with results that 



Figure 4.- 



RADIO FIELD-STRENGTH, 9-10 P.M., 75 WEST MERIDIAN TIME 

 WBBM, WABAN, MASSACHUSETTS, NOVEMBER 1935 THROUGH JANUARY 



1938 



-Field strengths of broadcasting station show a decrease trend with increasing sunspots. 

 of sunspot activity and ultraviolet light are inverted in plotting. 



Curves 



were far from convincing. Observations at other eclipses have un- 

 mistakably confirmed the hypothesis of ultraviolet light as a source of 

 ionization but only conflicting reports are available for any substan- 

 tiation of a corpuscular or electronic shadow. One difficulty, perhaps, 

 in detecting the effects of a stream of charged particles or electrons 

 emanating from the sun or sunspots lies in the fact that the paths of 



