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ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 5 



zon. Though the accuracies and the range of stations are not all 

 that are desired, the data present good indications of the general 

 characteristics and the magnitudes of the effect. 



10. ANALYSIS OF THE COSMIC RADIATION 



With the results of the directional measurements and those of 

 the variations of total intensity with latitude, together with the cal- 

 culations of the cut-off angles, we are in position to make a tentative 

 analysis of the primary cosmic radiation. The method of attack 

 and the results to be achieved are clearly before us, but the course 

 is not without its pitfalls. 



B'iGURH 5. — Combined results of the measurements of east-west asymmetries. Ratio of 

 east-west intensity difference to average intensity plotted against zenith angle. Sta- 

 tions arranged in order of their latitudes and elevations. 



St0rmer's solution of the cut-off angles is simple in form and 

 ready for application, but it fails to distinguish between rays which 

 are coming from infinite distances where sources of radiation exist 

 and those which might have described closed orbits in the vicinity 

 of the earth had there been sources of radiation near at hand. The 

 latter orbits are vacant and must be left out of account. Lemaitre 

 and Vallarta have studied these orbits and find that they would 

 illuminate a range of angles just inside the cut-off limit as it is 

 given by the simple St0rmer theory. It is also shown that within this 

 range of angles no infinite orbits reach the observer, and hence it 

 is only necessary to make a correction to the cut-off angle in taking 

 account of the vacant closed orbits. With this refinement of the 

 theory, the angles illuminated by rays of a particular rigidity cover 



