828 
lamellae were crossed at 120°, while attention was given to prevent 
a rotation of them through 180° about an axis perpendicular to the 
plane of cleavage. In these and the following preparations, the 
longer sides of the lamellae were always parallel to the geometrical 
plane of symmetry of the muscovite-crystal, contrary to what 
occurred in the mica-piles studied before. A normal image with a 
trigonal axis and three planes of symmetry passing through it, could 
be expected here beforehand. Because of the not wholly irreproachable 
material available, the patterns obtained were not suited for photo- 
graphical reproduction; but notwithstanding this, it was possible to 
confirm the exactness of this prediction completely. A schematical 
projection of these patterns, which also in this case appeared to be 
identical for the dextro-, and laevogyratory complexes, is reproduced 
in fig. 5. 
Fig. 5. Stereographical Projection (schematical) of the Réntcenpattern of 
dextro and laevogyratory Mica-piles, with Lamellae crossing at 120°. 
Finally in fig. 6 the stereograpbical projection is reproduced 
(schematically) of two diffraction-images, obtained by two different 
muscovite-piles. In the first complex the lamellae crossed at 
60°, and a rotation of the lamellae was carefully prevented; in the 
second preparation, however, the subsequent Jamellae included angles 
