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Transactions of the lioyal Society of South A frica. 
In order to test this, two specimens of Apopliyllite were irradiated 
nornially to their planes of cleavage. The first specimen showed a dis- 
continuity along a plane of cleavage. This discontinuity did not extend 
throughout the crystal, and could only be detected microscopically after 
very careful examination. The second specimen, for which I am indebted 
to Prof. Shand, was perfect. 
The interference pattern of the first showed a slight distortion of the 
points, which presented a nebular appearance (PL IV, Fig. 7), whereas the 
second specimen showed well-defined elliptic spots. 
{d) Diamond Tests by Eadiation Patterns. 
1. Made. 
± " Spotted Stone." 
3. Spotted Eejection Stone. 
4. Inferior Brown Block with black spot in it. 
I. The Made, 
which was examined some years ago, showed the usual pattern, together 
with a second one similar to the first, but rotated through 180°. This 
shows that the second lattice is similar to the first, but that it is rotated 
through two right angles. The spots in the pattern do not indicate any 
discontinuity in the lattice in the particular specimen (PI. IV, Fig. 8). 
2. " Spotted Stone.'" 
This stone, apparently perfect but for a small black spot in the interior, 
showed after an exposure of three hours that some of the spots in the 
regular pattern were affected by the presence of the spot in the crystal. 
The slight discontinuity in some of the spots is only revealed when the 
photographic plate is placed at a considerable distance from the crystal. 
The discontinuities in the various spots show that the disturbing 
influence is not the same for all the spots affected, but that the lattice of 
this stone as a whole remains perfect ; that is to say, that there is neither 
a fracture in the lattice nor a rotation of its component parts {vide PI. V, 
Fig. 9). 
At this point we wish to express our indebtedness to the De Beers 
Consolidated Mines for the loan of this stone. 
3. Spotted Rejection Stone. 
This stone, bounded by a fairly smooth octahedral cleavage plane, was 
irradiated normally to it. After an exposure of three and a half hours the 
pattern showed that the lattice was ruptured, so much so that the usual 
elliptic spots were represented by irregular discontinuous markings, spaced 
at various intervals. The diamond as a whole seems to consist of units 
