rR(U'.n:.iTi(>\ ()/• i-i.r.CTNic u.irns ornn riir. F.iRrii 22-^ 



orrasionalK', a ciriularl\' pnlari/i-d l>fam .it the riTfiver due to the 

 fact that the reteiving insirumfiU is locati-d at a iK)int toward which 

 oiu- of the Iwams is diverted after lia\iiin ()assed lhroii)^h an iip|HT 

 ioni/til layer. This is now hein^; investijjaled experimentally. It 

 is clear that, although the two components do not in general travel, 

 over the siune path, hoth ma>' e\enlually arrive at the same receivei'. 

 The first ray, however, ma\- iiave pi'netrated iniicli higher in the 



atmosphere than the other, that is, to a level at wiiich — has the 



(is 



prof>er negative value to cause it to return to earth. 



For long waves, these curvatures become: 



-f-?a. 



<:■,-, -J 



2«„-L (is h (is J 



Hence a limited beam of long waves entering this medium would tend 

 to split into two of opposite polarization and traverse different paths. 



In the special case for which ^.~- = -, — r~ throughout the medium, 

 .\ (is h ds 



there will be no such separation of the beam. 



F~or verv short waves 



" 2no=L 





Hence if the most effective cause of refraction is the variation in the 

 ionic density both components tend to remain together and to travel 

 with a rotation of the plane of polarization. If variation in the 

 magnetic field is appreciable the two components tend to diverge as 

 in the case of long waves. 



F'"or propagation at right angles to //, sav along .v, we have 



Mr =«•.!= 1- -.7. (!•■>) 



(16) 



