184 Robinson — Octahedrite and Brookite.' 



the following table. The scheme is that of Goldschmidt as 

 given in his " Krystallographische Winkeltabellen." 



Faces. 



Measured. 





Calculated. 



Error. 





<P 



P 









P 







P 



c (001) 



















a (100) 



89° 58' 



89° 58' 



90 c 



0' 



90° 0' 



¥' 



2 r 



m (110) 



49 55 



a a 



49 



55 



CC iC 







2 



a (320) 



60 50 



u a 



60 



42 



a u 



8 



2 



I (210) 



6V 13 



c< a 



67 



10 



(( tt 



3 



2 



h (410) 



77 52 



(C it 



78 



07 



a a 



15 



2 



d (043) 







51 28 











51 32 





4 



t (021) 







62 







62 06 





6 



2/ (104) 



89 57 



15 37 



90 







15 40 



3 



3 



x (102) 



u a 



29 15 



(i 



u 



29 18 



3 



3 



r (101) (new) 



a a 



48 18 



a 



u 



48 17i 



3 



o* 



v (146) " 



16 30J 



33 23| 



16 



32J 



33 18 



2 



H 



e (122) 



30 47 



47 38 



30 



43 



47 41 



4 



3 



z (112) 



49 53 



36 12 



49 



55 



36 15 



2 



3 



o (111) 



49 54 



55 47 



a 



a 



55 43 



1 



4 



fi (5-4-10) (new) 



55 55 



34 05£ 



56 



03 



34 04£ 



8 



1 



v (326) 



60 43 



32 44 



60 



42 



32 45 



1 



1 



o- (324) (new) 



60 46^ 



43 49 



a 



a 



43 59 



4i 



10 



s (322) 



60 42 



62 35 



a 



a 



62 36 







1 









Average error, 



81 



3 



In calculating the values of the four new forms given in the 

 foregoing table the axial ratio of a : 1 : e = 0*84158 : 1 : 0-94439, 

 as determined by Kokscharow,* was used. The form /3 (5-4*10) 

 was observed on one crystal (figure 5), three faces being pres- 

 ent on one end and two on the opposite, out of a possible four 

 in each case. The dome t (101) was observed but once on the 

 same crystal. The pyramids a- (324) and v (146) were observed 

 on but one crystal (figure 6), the first form being represented 

 by two and the second by three faces. 



Sheffield Laboratory of Mineralogy, 

 Yale University, New Haven, Conn., May, 1901. 



* Mineralogie Russlands, I, 61, 1853. 





