15538 
appear completely wrsymmetrical, with every orientation of the 
investigated crystal-plates. 
Of the triclinie-pedial class we had no representatives at our 
disposal; of the triclinic-pinacoidal class we investigated only the 
erystals of coppersulphate (5H,O), and of potassiumbichromate. 
Coppersulphate: CuSO, + 5H,O, possesses the following para- 
meters 206 —O121 212 0.5054) a $2254. == 1072384. y= 
= 102°41’. Potassiumbichromate: K,Cr,O,, can likewise easily be 
obtained in good, homogeneous crystals. They have the parameters: 
sore 0,00 to 10.551 1 se — OA Orr P9025 14 - 3 and 
a perfect cleavability parallel to {010}. Of both crystals planeparallel 
sections were prepared, parallel to the three pinacoides {100}, {010} 
and {001}; those of coppersulphate had a thickness of resp.: 1,08, 
1.03, and 0.94 mm., those of potassiumbichromate of: 0.68, 0.67, 
and 0.65 mm. 
The obtained Röntgen-patterns are reproduced in figs. 1, 2 and 3 
on Plate I, and in figs. 5, 6, and 7 on Plate Il. The unsymme- 
trical structure of these six diffraction-images is immediately discern- 
ible; it may be remarked, that in all six cases the superficial 
habit of the images is closely similar to those of monoclinic crystals, 
as far as those images are characterised by a single plane of sym- 
metry. However, the distribution of the spots and of their intensity 
is such, that there can be no doubt whatever about the lack of 
symmetry in the diffraction-images. 
The concordance of theory and experiment thus is proved suffi- 
ciently also for the case of triclinic crystals. It is of no importance 
to investigate more representatives of this kind and in the same 
way; thus our systematical experiments in this direction have reached 
an end here. 
§ 2. Only as a completion of our previous investigations we 
wish to publish however here again some results obtained with a 
number of rhombic minerals, namely with bronzite, diaspore, man- 
ganite, antimonite and olivine. 
After that we will again draw attention for a moment to the dif- 
fraction-images of dextrogyratory quartz, and this with respect to 
the anomalies of them formerly stated by us *). Some remarks on the 
RÖNTrGEN-pattern of brucite, and, as a completion of our previous 
investigations on monoclinic erystals®), — of lthiumsulphate, will 
end this paper. 
Bronzite is a rhombic pyroxene with the composition: (Mg, Fe),(Si0,), 
1) These Proceed., 18, 550. (Sept. 1915). 
2) These Proceed., 18, 1201. (Jan. 1916). 
