REPORT OF THE DIRECTOR I917 



159 



Forms. The following forms were recorded on the twenty crystals 

 studied : 



b (010), c (001), m (no), y) (320), X (210), /1 (034), 



(on), ; 3 (053)*, J (102), w (101), v (115),/ (113)1 z i 111 ), 



y (122), w (313), <f 2 (165)*, ^ (166), ^ 3 (167)*. 



The forms marked with an asterisk (*) are new. 



/1 (034). This brachi dome was present on most of the crystals 

 measured, as a series of narrow faces, giving poor reflections. 

 Although rare, (034) has been observed by Samojloff 1 on geodic 

 barite crystals from the .beds of the rivers Ischma and Uchta, 

 northern Russia, and by Slavic 2 from Mies, Bohemia. 



U (°53)- This new brachi dome was present on a number of the 

 crystals measured, as slightly rounded planes of fair development. 

 Although dim, the signals yielded consistent readings and there 

 seems to be little doubt regarding the validity of the indexes as 

 assigned. 



The above rare domes were identified from the following measure- 

 ments upon a single circle Feuss goniometer : 



Letter 



c:ji 



c:'h 



Symbol 



001 :034 

 001 :053 



Number 



of 

 readings 



Measured 



44" 29' 

 65 35 



Cal- 

 culated 



44" 34*' 



65 27 



Developing the zone of the brachidomes into an harmonic series 

 and splitting at the obvious knot point (on), we have for the 

 recorded brachidomes of barite: 



■ 6 5 A ? Y 1", £ 2 B £ 3 £ 



oc 



oc 



a 



Forms 

 Symbol 



V-Vi 



v 2 -v 



Forms 

 Symbol 

 v-i 

 2 



001 0.1. 1 2 018 016 014 013 025 012 047 035 023 034045 056067 08901 1 



1 



1 2 



1 1 



2l o- O 



5 6 8 



1 



on 053 021 



1 I 2 



3 



031 

 3 



x 

 041 



4 



_3 

 2 



/ 



07I 



7 



g 



O.IO.I 



10 



A 



0.16. 1 



16 



A, 



0.20.1 



20 



_1J_ 

 2 



b 

 010 



00 



00 



1 Samojloff, J., Verh. Min. Ges. Petersb. 1900, 2, 38, 323. 

 ' l Slavic, Fr., Abh. d. bohm. Akad. 1905. 19, 11. 



