large Crystals of Enstatite. 



383 



On the enstatite 

 of Breitenbach. 



On the hypersthene 

 of Laach. 



38i 

 34i 



Makrodiagonal edge =125 52 125 58i 



Brachydiagonal edge =127 36 127 



Lateral edge . . = 78 42 78 

 These angles give the following axis : — 



a (brachvdiagonal) : b (macrodiagonal) : c (vertical) 

 = 6-97016 : 1 : 0*57097 



for the Breitenbach meteoric enstatite, or 



=0-971326 : 1 : 0*57000 



for the hypersthene of Laach. 



The faces represented in the figures receive the following 

 formula if we refer to the preceding axes : — 



Des Cloiseaux. 



u = 

 x = 

 m — 



a : ■#( 



: b : c), 2P2 ... 

 2b: c), P2 



c), §P| ... 

 Ja : & : c), 2P ... 

 aib: 00c), ccP .., 

 ocP2 

 00 P2 



bi 

 a 3 

 n 



yon Lang-. 

 112 

 122 

 124 



111 

 110 

 120 



iPoo e 4 



iPoo.... e 2 



QcPod h 1 



ooPco 



OP 



104 

 010 

 100 

 001 



= (2a : b : ccc), 



a : 26 : occ), 



h =( cca : Ah : c), 



( cca : 2b : c), 



a = {cc : cob : 00c), 



b = ( cca : b : ccc), <xr co g J 



c ={cca : ccb : c), OP p 



There was only one angle on the crystals of Kjorrestad which 

 could be measured with the reflection-goniometer — that is to 

 say, the angle of the two cleavage-faces, =91° '25'-91° 40'. 

 Yon Lang determined this angle on the enstatite of Breiten- 

 bach = 91° 44 x . On the hypersthene of Laach I found this 

 angle = 91°40 / ; whilst Des Cloiseaux gives the angle = 91°32J / 

 for the hypersthene of Capucin, as the mean of several mea- 

 sures. All the other angles of the Kjorrestad crystals can 

 only be measured with the contact-goniometer, and even 

 that only approximately, in consequence of the striation, the 

 arching, oscillation, and repetition of the faces, sometimes 

 already decomposed. 



One of the largest crystals in the Museum of Christiania 



