524 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 51). 



(2.10.5) Measured ^ = 18° 41' p = 69°41' 



Calculated tp = 17° 24' p = 69° 24' 



A= 1° 17' A = 0° 17' 



This form therefore is poorly established by the data obtained. 

 x t (342) occurred on crystal 27 as a small brilliant face yielding an 

 excellent signal. The angles are: 



(342) Measured «? = 49° 04' p = 75°41' 

 Calculated </> = 49° 45' p = 75° 41' 



A= 0°41' A = 0° 00' 



Although observed only once, the form is considered to be well 

 established. 



6 (343) occurs on crystal 33 as a distinct though narrow line face 

 between -k (231) and e (Tl2), as shown in figure 24. The signal, 

 owing to the narrowness of the face, was too faint for precise measure- 

 ment. The angles measured are: 



(343) Measured ^ = 49° 36' p = 70° 29' 

 Calculated <p = 49° 45' p - 69° 03' 



A= 0°09' A= 1° 26' 



The form is normal in zone No. 12, as shown below, and is con- 

 sidered as established, the indices being confirmed by zonal relations. 



T (351) occurred on crystal 33, as shown in figure 24, as a distinct 

 line face between it (231) and o (120). The very faint signal from 

 the partially etched face gave as angles: 



(351) Measured <p = 42° 32' p = 83°45' 



Calculated <p = 43° 17' p = 83° 26' 



A= 0°45' A= 0° 19' 



e t (353) occurred on crystal 33, as shown in figure 24, as a small 

 and very much etched face. The signal was very faint, and the 

 measurements are only approximate. The angles are: 



(353) Measured ^> = 44° 20' p = 68°58' 



Calculated ^ = 43°23' p = 73°58' 



A= 0° 57' A= 5° 00' 



The large discrepancy, A = 5° 00', is attributed to the difficulty of 

 measuring so badly etched a face. The indices are confirmed by the 

 zonal relations. 



