424 



Dr. L. Vegard on 



the amplitudes calculated from the lattice and those found 

 from the observed intensities. 



The arrangement would give a normal spectrum for the 

 (001) face, which is in good agreement with observations. 

 The expressions for the amplitudes of the other four faces 

 are given in equation (12), p. 85, of my second p;iper. 

 Inserting the values of the atomic numbers, and putting 



«, = 135, 



« 2 = 75, 

 we find the amplitudes given in Table VII. 



Table VII. 



ai = 135°, * 2 = 75°. 





Face... 



(HI). 



(110). 



(100). 



(101). 



Order. 













H 



A . 



A z - 



A - 



A f 



A, 



Az- 



A . 



1. 



19 



15 



100 



100 



100 



100 



100 



100 



2. 



35 



30 



105 



121 



114 



138 



87 



100 



3. 



40 



40 



in 



132 



135 



127 



116 



95 



4. 



100 



100 















Az is the amplitude calculated from the lattice. 

 A „ ,, ,, intensities. 



s/l 



As mentioned in my previous paper, there may be some 

 uncertainty with regard to the value k for the various 

 orders. Even for the same crystal, k may show a different 

 variation with the order number for different faces. 



In the previous papers I have put 



ifej = 1, k 2 = 0-2, h = 0-07, k A = 03. 



In the case of tetramethyl-ammonium iodide, we found 

 that the best agreement was obtained by supposing that 

 k n did not decrease quite so rapidly with increasing order. 



Also in the case of xenotime the values above, as already 

 stated in my previous paper, would give a much too strong 

 first-order spectrum as compared with that of the fourth 



