820 
Fig. 35. Stereographical Projection of the abnormal Diffraction-image of a dextro- 
or laevogyratory Complex of Muscovite-lamellae, crossing at 45°. 
of fig. 1 of this plate, while the text-figures 2a and 26, respectively 
3a and 35, represent stereographical projections, immediately relating 
to these diffraction-images. In all experiments the time of exposure 
of the photographic plates was two hours. 
Secondly, we can remark, that the normal RöNtGEN-images of 
fig. 2a and 3a show a perfect hexagonal, respectively octogonal sym- 
metry, evidently consisting of a pattern repeated siz, respectively 
eight times, the structure of which is, however, in the hexagonal 
image clearly diferent from that in the octogonal image, although 
the absorption of the RönrceNrays in these very thin lamellae plays 
only an insignificant part. Evidently the character of the composing 
patterns is here dependent in some way or other on the special 
way in which the secondary waves, emerging from the upper 
lamella, are modified by their passage through the next following 
lamella; and from this experience it seems, that this influence varies 
with the magnitude of the crossing-angle of two subsequent lamellae’). 
1) On the modifications of a primary RöNTGeN-pattern, if a secondary ray of 
it passes through a second and identically orientated crystalplate of the same sub- 
