342 



University of California Piibl ications. 



[Geology 



The elements according to the system of Goldschmidt, as 

 a: c = 1: 0.7344 (GJ, are as follows: 



(10) 



c = 0.7344 | lg e = 9.86593 | lg a = 0.37263 | lg p„= 9.68984 | a =2.3585 | p„= 0.4890 Gr 2 



or by selection of the other set of axes, 



c = 1.2720 | lg c = 0. 10449 | lg a„=0. 13407 | lg p =9. 92839 | a =1.3617 I p o =0.8480 G 



Table of Angles. Gi. 



No. 



Let. 



Gi 



o 2 



Bravais 



<t> 



P 



Co 



Vo 



f 



V 



X 



Prisms 



X 

 !l 



(1 



V 



d 



=tgp 



1 



c 











0001 





0°00' 



0°00' 



0°00' 



0°00' 



0°00' 













2 



. a 



OO 



oo 



1120 



30° 00' 



90 00 



90 00 



90 00 



30 00 



00 00 



0.5773 



oo 





CO 



3 



in 



4-eoO 



4- CO 



10T0 



II 00 



90 00 



00 



90 00 



00 



90 00 











oo 



4 



M 



-ooO 



00 



01 To 



60 00 



90 00 



90 00 



90 00 



60 00 



30 00 



1.7321 



oo 





oo 



5 



V 



+ 10 



+1 



loll 



o oo 



40 18 



00 



40 18 



00 



40 IS 



1) 



0.8480 



0. 



8480 



6 



7T 



— 10 



-1 



OlTl 



60 00 



40 18 



36 19 



22 59 



34 04 



18 52 



0.7349 



0.4240 







8480 



7 



r 



+io 



+* 



10T2 



00 



22 58 



00 



22 58 



00 



22 58 







0.4240 



0. 



4240 



8 



d 



9 



60 



2241 



30 00 



71 12 



! 55 45 



68 32 



28 15 



55 ill 



1.4087 



2.5440 



2. 



9375 



A number of crystals show a more complicated form that 

 lies vicinal to v and in the angle where v, m and p meet. These 

 faces may occur complete for the symmetry as far as one face ir 

 and its corresponding face vertically below are concerned — that 

 is, one in each of the corresponding p, it, m corners; but they 

 have not yet been found corresponding to the complete sym- 

 metry of a whole crystal. They are uniformly dull, and give 

 no opportunity for accurate measurement. Many attempts at 

 measurement were made with unsatisfactory results, and the fol- 

 lowing approximation may be given : x = — (10 1 9 10) . At 

 least one other was observed, and recognized as different by the 

 different triangular trace that it produces, but it is so near tt in 

 its attitude and so dull that no approximation is attempted. 

 x seems to be the more common of the vicinal forms and was 

 observed on a number of crystals. It is of interest as the best- 

 defined representative of a general form yet observed. 



The positive set of planes give much better reflections than 

 the negative set. ft (1010) gives generally unsatisfactory re- 

 flections. The unit pyramid faces ± should show the simple 

 relation that one appears at each (</>-)-n60) with the same 



