I 



SoLLAS — Oil the Crystalline Form of Riehecldte. 519 



marked anomalies of form. In none does the angle between the basal 

 plane and clino-pinacoid measure exactly 90° ; it is almost always in 

 excess to tbe extent of from 2' to 15', and thus might lead one to 

 imagine that the mineral should be referred to the anorthic system. 

 Further examination shows, however, that the defect of symmetry is 

 as little consistent with the anorthic as with any other system. Thus 

 measurements in the [100] zone gave the following^ : — 



010 



: 001, 



I. 



89°41' 



II. 

 89° 57' 



HI. 



89° 57' 



IV. 



89° 48 



001 



010, 



89 bb 



89 50 



89 37 



89 54 



179° 36' 179° 47' 



179° 34' 179° 42' 



In the zones [110] and [110] :— 



180° 19' 



In the zone [101] ;- 



110 



001, 



I. [110] 

 77° 47' 



I. [110] 

 77° 53' 



III. [110] 

 78° 15' 



110 



001 



001 



111, 



34 10 



34 2 



34 21 



001 



ill 



111 



110, 



68 22 



67 44 



68 3 



111 



110 



179° 39' 180° 39' 



010 



111 



74° 14' 



Til 



ill 



31 14 



111 



olo 



74 7 





179° 35' 



the zone [112] :— 





110 



021 



65° 28' 



021 



111 



31 37 



111 



201 



27 54 



201 



110 



54 42 



179° 41' 



^ The Roman numerals i. ii., &c., refer to the number of the specimen 

 measured. 



