Notes on Radiatioyi Patterns. 
61 
The pattern clearly indicates that the lattice of Serpentine has symmetry 
in a definite direction relative to the threads ; hence it cannot be triclinic, 
which shows no symmetry whatsoever,* in interference patterns, except 
when it is uniformly twinned. 
Malachite. 
Secondly, a plate of Malachite, cut parallel to the slightly radiating 
fibres, was examined. After an exposure of three hours, the pattern showed 
three lines parallel to the threads and a number of secondary lines perpen- 
dicular to the principal line. 
The two lines parallel to the principal line are faint in comparison with 
the principal line and the short secondary lines {vide PI. Ill, Fig. 5). 
Pseuclomorph Quartz (Crocidolite). 
A plate of Pseudomorph Quartz was examined, and the photogram, 
after an exposure of six hours, showed an intense dispersion round the 
central spot, accompanied by thin radial lines, making a small angle in the 
direction of the threads. This seems to indicate that this substance is 
microcrystalline and that the miniature crystals are so orientated that their 
normals to their reflecting planes favour the direction of the threads 
(vide PI. Ill, Fig. 6). 
Experiments on minerals of a similar nature are still in progress. 
As far as these observations go, they seem to indicate that though the 
crystals show the characteristics of microcrystalline substances, nevertheless 
they also indicate that the elementary units still favour particular direc- 
tions, and these directions give an index to the nature of the original lattice. 
These radial lines indicate the loci of the principal points of the point- 
pattern of the original crystal, and also give an indication of the stability 
of the lattice. 
Thus a new field of research is opened with regard to the transition 
stages in crystals. We wish to thank Prof. Young for supplying us with 
the specimens. 
(c) BULTFONTEIN ApOPHYLLITE. 
In an earlier communication it was shown that a slight displacement 
of any cleavage planes within the crystal would cause an irregular distribu- 
tion of the intensity in any individual spot to which that plane under 
ordinary conditions contributes its share of reflection, i. e. the intensity 
which it would have added to a definite part of the spot is now reflected to 
some other position, consequently irregularities caused by cleavage cracks 
will produce irregular spots. f 
* Haga and Jaeger .- ' Proc. Kon, Akad.,' Amsterdam, 15, 1552, 1916. 
t ' Trans. Roy. Soc. South Africa,' vol. v, part 5, 571, 1916. 
