Goldschmidt and Nicol — New Forms of Sperrylite. 455 



complied with ; that is, the numbers form a legitimate series. 

 We have the following discussion of the numbers :* 



Letters 





C 



g' 



b- 



6 



e 



Symbol 

 P 



pq 





 



|0 



2 

 "5" 



fo 



2 

 3 



10 



1 



20 



2 



P 



2 



— 







JL 

 5 



1 

 3 



* 



1 



vf 



1 -V 



= 







JL 



4 



1 

 2 



1 



00 



2v 



=z 







1 



1 



2 



00 



normal series JN"2. 



h = + f (305) observed on the peculiar crystal ]N"o. 6 (fig. 5), 

 along with the form c = 0. The faces are very narrow 

 and in consequence of this the signal reflections are some- 

 what extended in the zone ; still the form may be con- 

 sidered as established since it occurs on all the edges, and 

 the middle position corresponds to that obtained by calcu- 

 lation. Confusion of this form with the neighboring one 

 e == .+ \ is not possible and, moreover, e occurs beside h 

 on two edges. For determining the symbol the angle 

 formed with the adjoining cubic face suffices. This gave 

 for the nine faces capable of being measured the follow- 

 ing values : 



h:c = 30° 33; 30° 35 ; 30° 28 ; 31° 02 ; 31° 37; 31° 39; 31° 58 ; 



30° 29 ; 30° 53 

 Average, measured =30° 53 

 calculated = 30° 58 



This crystal is peculiar in that the form p, the octahedron, 

 is entirely wanting and the form e as compared with h is 

 unimportant. 



k = i (114) observed on crystal No. 5 with two small faces, the 

 better of which gave the position : 



measured : cf>p = 13° 46 ; 76° 01 

 calculated : d>p= 14° 02 ; 76° 22 



This form occurs again on crystal JNo. 7 with one face 

 which is uncertain, however. 



m = i (113) observed on crystal jNTo. 1 with two small faces in 

 the zone c p, the better of which gave the position c m = 



* Concerning such a discussion of numbers compare Zeitschr. f. Kryst., 

 xxviii, 24, 1897. 



f v indicates always the member of the previous series which is to be 

 transposed to the corresponding one of the following series. 



