COSMIC RADIATION — JOHNSON 



209 



wider areas of the sky on the equatorial side of the east-west vertical 

 plane, and a north-south asymmetry would be expected. Measure- 

 ments in Mexico, represented in figure 6, show greater intensities 

 from the south and confirm this detail of the calculation. 



On the basis of Lemaitre and Vallarta's first estimates of the true 

 cut-dlf angles of infinite orbits, the experimental results led to the 

 tentative conclusion that the primary radiation was practically all 

 positive, and nearly uniformly distributed with respect to rigidity. 

 Recent investigations by the same authors, in collaboration with 

 Bouchaert have resulted in more accurate determinations of the true 

 cut-ojff angles in the range of latitudes from the Equator to 20°, 

 but the theoretical work is not yet complete for higher latitudes. 



Without further consideration it is 

 clear from the western excess of intensity 

 that much of the charged component con- 

 sists of positive rays unbalanced by neg- 

 atives. Analysis of the asymmetry meas- 

 urements in the equatorial zone shows 

 that 14.2 percent of the intensity at 4,300 

 meters is due to positives unbalanced by 



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negatives in the range of rigidities below 



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PiGDKB 6. — North-south asymmetry 

 of the cosmic ray intensity in 

 Mexico, latitude 29°, elevation 

 4,300 meters. 



that which cuts off in the east. At the 

 same elevation in Panama 16.9 percent 

 of the intensity is due to radiation below 

 the same limit of rigidity and similarly 

 defined. The higher value for Panama 

 is due to the slight eastward shift of cut- 

 off angles for each rigidity and the in- 

 clusion of lower rigidities from the west. 

 The difference in these figures (16.9% — 

 14.27o = 2.7%) is the change of the total 

 intensity in this range of latitude which can be accounted for by 

 unbalanced positive radiation. If the figure should agree with the 

 measured change of intensity we could conclude that all of the latitude 

 effect in this range can be accounted for by positives and that there 

 is no negative component in this range of rigidity, contributing to the 

 intensity at that elevation. Because of the absence of high mountains 

 in Panama, accurate measurements of the latitude effect are lacking 

 but the airplane measurements of Bowen, Millikan, and Neher show 

 that the change of intensity in this range is small and probably does 

 not exceed 4 or 5 percent. If the latter value is chosen as an upper 

 limit, the difference between 5 percent and the 2.7 percent accounted 

 for by unbalanced positives, must be accounted for by a balanced 

 component of positives and negatives in equal numbers. Thus the 



