1213 
patterns obtained are reproduced. When perpendieular to the c-axis, 
the photograph, remained very feeble even after 34 hours’ exposure ; 
in both the other principal directions however, even after much 
shorter exposure, the photographs were very sharp. 
The plate perpendicular to the c-axis, in fact shows two normal 
planes of sy LoS ONE as well as the binary axis: in the direction of 
i 1 5 a — LANAANNN Nonnen Je |) Wein inten dn 
ERRATA. 
In the paper of F. M. Jarcrr: A new Phenomenon accompanying 
the Diffraction of R6nrGEn-rays, ete. the following errors must be 
corrected : 
On Table IV Fig. 10. Plate parallel (010). Read: Plate parallel (001). 
Fig. 11. Plate perpendicular to the c-axis. Read: Plate 
parallel to the 6-axis. 
A comparison with the photo’s 8 on Table II and 9 on Table III 
will also immediately make this evident. 
In connection herewith, on p. 1213, in the 19" line from the 
top, in stead cf Fig. 11 should be read: Fig. 10. 
a- and b-axis 15 only sligttly different in it. 
Both pinacoides {100} and {010} have thus in an optical sense 
about the same relation to the direction of the c-axis, and therefore 
we observe that the plane of symmetry parallel to (001) disappears 
on the corresponding photos. In both plates the spots which lie 
in directions parallel to the greater elasticity have thus disappeared 
completely, just as in the case of hambergite. 
$ 7. Finally we point out the peculiarities found in the study 
