1554 
and the parameters; a: 6: ¢ = 0,9702: 1: 0,5701. Three plates parallel 
to (100), (010) and (O01) and resp. 1,09, 1.10, and 1.06 mm. thick, 
were cut from a beautiful erystal of Kupferberg, Bayreuth. The 
plate parallel to (O10) showed a slight deviation from its normal 
orientation; the RÖNTGEN-patterns are reproduced in fig. 9, 10, and 
11 on Plate Il, and in stereographical projection in fig. 1, 2, and 
3 on Plate V. The symmetry with respect to two perpendicular 
planes is immediately discernible. 
For the purpose of comparison of diaspore and manganite, also 
from these minerals sections parallel to the three pinacoides were 
cut and radiated through. In the case of diaspore: AlO(OH), with 
the parameters: a: b:c =0,4686:1:0,3019, and originating from 
Emery Mines (Mass.), only the image parallel to (010) was suitable 
for direct reproduction (fig. 4 on Plate I); the corresponding stereo- 
graphical projections, also for an image parallel to (001), are repro- 
duced in fig. 4 and 5 on Plate V. The thickness of the used plates 
of diaspore was resp. 0,96, 0,93 and 1,02 mm. In the case of 
manganite (from Llfeld, ijd Harz) patterns were obtained, showing 
instead of spots, long radiating stripes. This fact was also stated by 
us in the ease of godthite; it seems to be connected partially with 
contusions of the material, and with intergrowths and twinning of 
fibre-shaped individuals in these crystals. Hitherto we were not able 
to get undisturbed diffraction-images suitable for clear interpretation. 
Of manganite: MnO(OH), whose parameters are: a: 6: c = 0,8441 : 
1: 0,5448, only a somewhat reliable projection could be made for 
the image obtained parallel (100); the thickness of the erystal-plate 
used was here 1,04 mm., and the figure is shown in fig. 6 
on Plate V. 
Of antimonite: Sb, S,, with its parameters: a:6:c=0,9844:1: 
1,0110, we had the very beautiful crystals of Shikoku Japan, at 
our disposal, the same, which were formerly used in the investiga- 
tions of one of us‘), on the influence of the light-radiation upon the 
electrical conductivity of this in so many respects remarkable mineral. 
We studied a lamella, obtained by cleavage parallel to (010), which 
was not thicker than 0.43 mm. Notwithstanding the presence of a 
number of folds parallel to the sliding-plane (OO1) the obtained 
diffraction-image yet appeared to be perfectly undisturbed; it is 
reproduced in fig. 16 on Plate IV, and as a stereographical projection 
in fig. 7 on Plate V. This fact could be used as an argument in 
favour of the correctness of the view, according to which such 
sliding along perfect sliding-planes, does „ot alter the internal arran- 
DF. M. Jareer Zeits. f. Kryst. 44. 45. (1908); these Proceed. 9. 809. (1907). 
