Mr. J. N. Lockyer's Spectroscopic Notes. 



r 



325 



Fig. 4. 



Fig. 5. 



5. Although, in the preceding drawings, I have represented this 

 unilateral widening exclusively on the more refrangible side of D, 

 I have observed it on the other, though scarcely so frequently. 



6. Accompanying these appearances, but generally best visible 

 when the absorption with curved boundary is visible on both sides 

 of D, is a brilliant boundary replacing the mere change of shade. 



7. At times the brilliant boundary is continuous across D, as 

 shown in fig. 6 ; but I append figs. 7 and 8 to show that the phe- 

 nomena on either side of D are independent of each other. 









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