184 



faces being too poor to give a reflection; the necessary 

 angles were eitiier measured with the contact goniometer 

 or with a microscope. The observations made with the 

 mineral, which is imbedded in the neighboring rock were by, 

 far not as good as the above and therefore cannot be taken 

 into consideration. The mineral being extraordinarily brittle, it 

 is impossible to separate it from the surrounding minerals, with 

 which it is connected, without breaking it. The impressions of 

 the faces of the epistolite , which were found , are always 

 too indistinct to make it possible to measure them with exact- 

 ness, and consequently the following results can only be con- 

 sidered approximately accurate: 



Fig. 1. Epistolite. 



Crystallisation monoclin i с 

 ß = 7/1° 45' = (001) :(I00) 

 à:b:c = 0-803 : I : 1-206 



The following were used as fundamental angles: 



Average value 

 (001): (110) = 78° 0' 

 (001): (Oil) = 49° 20' 



Number of 

 measurements 



4 



Variations 

 76°— 80° 



48°— 50° 



further on cleavage faces the angle, which the traces of (llO) 

 and (iTo) make on (00 1): 



Number of 

 measurements Variations 



13 99° -105° 30' 



Average value 

 = 102° 30' 



