88 



Dr. L. Vegard on 



Now in order that the oxygen atoms may considerably 

 reduce the intensity of the first order spectrum ft + a 2 must 

 be considerably smaller than tt, and we should expect both 

 a 2 and ft to be in the first quadrant, somewhere between 

 25° and 90°. 



To determine ft and « 2 more accurately we could calculate 

 the intensities for varying values of /3and a 2 . We can arrive 

 at fairly good values more quickly by means o£ a graphical 

 method. We can very quickly draw curves representing 

 cos nft ■+■ cos noc 2 for various values of ft, ot 2 and n. In fig. 7 

 the curves are given for ft = 60° and for values of a 2 varying 

 from 0° to 180°, and for n=l, 2, 3, 4, 5, 6. 



In this way I have found that the following values will 

 give the best agreement with observations : 



ft = 30°, a 2 = 60°. 



In the formula for f\(n) of the face (111) and also for the 



