76 Prof. L. Vegard: Results of Northliglit Investigations 



and the corresponding air equivalent r at various heights o£ 

 the atmosphere are given in Table X. . 











Table 



X. 











Hydrogen. 



P: 



Helium. 



Nitrogen. 



Oxyg 



en. 



Height. 



p. 



r. 



V- 



r. 



r. 



km. 



dyn/cm. 



2 cm. 



dyn/cm. 1 



cm. 



dyn/cm. 2 



cm. 



dyn/cm. 2 



cm. 



400.. 



. 0-44 



1-30 



o-ooi 



00015 











300.. 



. 1-30 



3-87 



0-U08 



00126 











200.. 



. 3-85 



11-48 



0071 



107 











160.. 



. 5-95 



17-73 



0169 



0-254 











140.. 



. 7-29 



22-1 



0-259 



0-390 



0-0006 



00005 







130.. 



. 8-24 



24 6 



0-321 



0-483 



0-0026 



00021 







120.. 



. 9-20 



27-4 



0-399 



0-600 



0-0121 



0-0097 



0003 



00002 



110.. 



. 1025 



30-6 



0-494 



0-743 



0055 



0-0443 



0-0013 



00010 



100.. 



. 11-4 



34-1 



0611 



0-919 



0-251 



0-202 



0-0080 



0062 



95.. 



. 121 



36-0 



0-681 



002 



0-520 



0-425 



0019 



00142 



90.. 



. 12-7 



37-9 



0-757 



0-14 



1-14 



0-918 



0045 



00335 



85. 



. 13-5 



40-2 



0-843 



1-26 



2-43 



1-96 



0-107 



0-0797 



80. 



. 14-2 



42-4 



0-939 



1-40 



. 5-21 



4-18 



0-254 



0190 



75. 



. 15-0 



447 



1-045 



1-56 



111 



8-91 



0-602 



0-451 



70. 



. 15-9 



47-4 



1-16 



1-74 



237 



19-1 



1-44 



1-08 



05. 



. 16-8 



500 



1-3 



2-03 



50-5 



40-6 



3-42 



2-56 



00. 



. 17-6 



52-7 



1-45 



2-27 



107-7 



86-5 



810 



6 07 



55. 



. 187 



55-7 



1-60 



2-51 



229-9 



I486 



193 



14-6 



50. 



. 19-7 



85-7 



1-7.9 



281 



491-5 



394-7 



45-8 



34-3 



If the rays form an angle a with the vertical we get, 

 as we can easily see, the corresponding air equivalent at 

 any height by dividing the values given in the table 

 with cos «. 



Thus, if the magnetic field were uniform and the rays 

 were moving along the lines of force, the air equivalent 



at any point would have to be multiplied with ~ — r , 

 J * l sin r 



where I is the magnetic inclination. Near the auroral 



zone — — t is equal to about 1*06, so the values of r in 

 sin 1 ^ 



Table X. give practically the air equivalent of rays moving 



along the lines of force. If, however, the rays form an 



angle a. with the lines of force, the air equivalent at a 



point has to be multiplied with — — , and if a approaches 90° 



— approaches an infinitely large value, and a ray moving 

 in spirals round the magnetic lines of force may be stopped 



