some Carbonates of the Calcite Group. 



329 



In the case of calcite and rhodochrosite only those 

 planes are f onnd reflecting for which the value of H K • L 

 fulfills the following conditions 



211 + K + L 



= whole number 



K- H + L 



= whole number 



-2K-H + L 



= whole number 



d 



r 



M 

 •it 



i i 



•-n 



i-l-4- 

 I I I 

 ! — h— 1— 



ri~f- 

 j-Li 





^ 



I L4-- 



tCW-H- 



I , f — 4 — — — ' 



-M-r .. 



-H-M-- ••• 



-i 



-i 



'--^-r 



— I- — 



L-L-v— 



4-1 ' 



— I- 



I I 



-H-" 



I 



I 



r~— r--J 





-H--L 



r 



i i 



-+-- . 



K4. 



-M 



i 



-t-Hfc-j 



I 



T—4— 



-it J 



H 



~n-- 



--— 1 



-—*" 



I 



— -r 

 i 

 — *-- 



i 



_---t-- — n 



— -H * 



-t T" f 



I 



H% 



!• il- 





h— -- 



V' 



-U. 



7-- 

 I 



I 



I 



'^^ 



--J 



Fig. 7. — The gnomonic projection of an unsymmetrical Laue photograph. 

 The rays were passed through the section of rutile used for Figure 6 at a 

 considerable inclination to the c-axis. There is no difficulty in getting the 

 indices of these planes. 



The preponderance of such planes is to be expected when 

 the fundamental lattice is rhombohedral but not when it 

 is hexagonal, and serves as a convenient criterion for 



