1202 
Although the obtained patterns were very regularly built, they 
appeared to be too feeble for immediate reproduction. However, in 
fig. 1 to 3 of Plate VI their stereographical projections are published. 
In a quite analogous way crystals of cane-sugar: C,,H,,O,, were 
studied; their parameters are: a:b:¢=1,2595:1:0,8782, and 
3 = 76°30'. In the case of the erystal-plate parallel to (100) the 
thickness was: 1,86 mm.; that parallel to (O10) was 1,88 mm., 
and that parallel to (001) was 1,81 mm. thick. The obtained photos 
are reproduced in fig. 1 to 3 of Plate i, and in stereographical 
projection in fig. 4, 5, and 6 of Plate VI. 
From an aqueous solution of d-rhamnose, magnificent Instrous and 
faultlessly shaped erystals were obtained, and here also plates parallel 
to the three pinacoides were cut out of them. The axial ratios of 
these crystals, whose chemical composition is :C,H,,0, + H,O (mtpt: 
93° C), were: a@:6:¢c=0,9998:1:0,8435, and @= 84°35’. The 
erystal-plate parallel to (100) had a thickness of 1,91 m.m. ; that parallel 
to (010), of 1,95 m.m., and that parallel to (001) of 1.93 m.m. The 
obtained patterns are reproduced in fig. 4 on Plate I, and in fig, 5 
and 6 on Plate II; their stereographical projections in fig. 7,8, and 
9 on Plate VI. 
From all these experiments it can be clearly seen, that notwith- 
standing the fact, that these crystals possess only a single binary 
axis, their R6nreEN-patterns parallel to (100) and (001), however, 
always manifest a plane of symmetry, while that parallel to (010) 
shows a binary axis, manifesting itself in the image as a centre of 
symmetry. Thus it is proved, that these patterns possess the same 
symmetry, as if they were obtained with monoclinic-prismatic crystals. 
§ 3. LU. Monochnic-domatic Class. 
After many tentatives we were able to get some crystal-plates 
from a small, simple scolezite-erystal from Teigarshorn in Iceland. 
It is very difficult to find crystals of this mineral, — whose com- 
position is: CaAl,Si,O,, + 3H,O, and whose axial ratio is: a: b:¢= 
0,9764 : 1: 0,8434, with @ = 89°18', — which appear not to be twins 
or multiplex crystals. The thickness of the small plates was as follows : 
for that parallel to (100), it was 0,78 m.m., for‘that parallel to (010) 
0,76 m.m., and for that parallel to (001), 0.83 m.m. 
Of the resulting photograms we have only reproduced here the 
image parallel to (001), in fig. 7 and Plate II, while the correspond- 
ing stereographical projections are reproduced in fig. 10 and 11 
on Plate VL. 
Notwithstanding the close approximation of the symmetry of this 
