194 Mr. K. W. James on the 



2. The observations were made with the X-ray spectro- 

 meter, arid the K a radiation from a Ooolidge bulb with a 

 rhodium anticathode was employed. The spectra from the 

 (100), (111), and (111) faces were examined. Owing to 

 the high absorption-coefficient of bismuth for the rhodium 

 rays, the spectra were not particularly intense, and not more 

 than three orders could be observed from any face. Metallic 

 bismuth is rather soft, and the crystals are easily distorted, 

 so that it was found impossible to prepare a good face by 

 grinding. All the ground faces examined gave reflexions 

 over a large range, in many cases over six or eight degrees, 

 as the crystal was turned, and for this reason it was not 

 possible to obtain reliable intensity measurements. The (100) 

 face used was ground on a crystal, the face being afterwards 

 etched with nitric acid to remove the distorted fragments of 

 metal produced by the grinding. The (111) and (111) faces 

 were obtained by cleavage from a large mass of crystals. 

 The relative intensities of the different orders of spectra 

 from these faces are probably fairly reliable, but very little 

 idea of the relative intensities of reflexion from the different 

 faces could be obtained. 



The positions and relative intensities of the spectra are 

 given in Table A. 



Table A. 



Face. Order. Glancing Angle. Relative Intensities. 



(100) 1st. 5° 25' 100 



2nd. 10° 52' 40 



3rd. 16° 30' 10 



(HI) 



(Hi 



The intensities are only approximate, and are expressed in 

 terms of the strongest spectrum for each face. No com- 

 parison of the relative intensities for different faces is given. 

 The first-order spectrum (100) is almost certainly too low in 

 comparison with the second, since the effect, due to a distorted 

 surface layer will be far greater for the smaller glancing- 

 angles. 



3. The observed glancing-angles for the first-order spectra 

 were 



(111) (100) (ill) 



4° 29' 5° 25' 4° 45' 



1st. 



4° 29' 



29 



2nd. 



8° 54' 



100 



3rd. 



13° 26' 



24 



1st, 



4° 45' 



10 



2nd. 



9=27' 



100 



3rd. 



— 







