ard. -y JOURNAL OF SCIENCE. 
I was gratified, however, to observe the fine crystal represented 
in Figs. 5a and 5b—a penetration twin of two crystals of the 
general form just described, but more symmetrically developed, 
and showing in addition the planes z and 6, the former of which, 
according to measurements with the hand goniometer of angle o: 
n=144°30' (Naumann 144°56’) agrees with the hemi-pyramid % 
P 2 (123); ‘whilst 6, which could not be satisfactorily measured, 
may possibly be the rare plane % P 4/; (4.36) determined by 
Hessenberg. The indented angle y: y’ was found to be about 
120° (Naumann 120° 34), and that of x: x’ about 102° (Nau- 
mann I0I° 26’). Owing to the brittleness of the mineral this 
crystal suffered considerable damage in transport. Judging 
from the impression left in the chlorite rock it must originally 
have been of an uncommonly large size, viz. good 11%” long, 
1” broad, and nearly 1%” thick ; the parts broken away are in- 
dicated by dotted lines in Fig. 5b. The breaking away of 
certain portions revealed, however, the interesting fact, conclu- 
sively proving the secondary nature of the mineral, namely, that 
one half of the twin has grown over a crystal otf orthoclase pro- 
truding from the chlorite rock ; the exposed feldspar portion is 
shown in Fig. 5b by shading. As all the specimens of the 
mineral have hitherto come from the chlorite rock cropping out 
on the seabeach, within range of the tide, which no doubt con- 
tributed to their fractured character and the injuries they sus- 
tained, it is very probable, in view of the fine development and 
size of the crystal just described, that at greater depth in the 
rock, or out of reach of the sea, really fine crystallizations of the 
mineral will be met with. 
Epidote.—Of this mineral Mr. Docherty found two varieties, 
both rather uncommon in form, colour, and lustre. 
Ist variety: This occurs in stout prismatic crystals, and largish 
patches of irregular outline in a large reef of white granular quartz, 
traversing Cooper’s Island, Dusky Sound. -It is of a greyish green 
colour, and has a strong greasy lustre in fracture. The prismatic 
crystals show no determinable planes at the ends, and owing to 
one appearing in cross-section in the quartz like a square prism 
with truncated vertical edges, I mistook the mineral at first for 
Vesuvianite, to which determination its behaviour before the 
blowpipe also conformed.* Finding later on that the mineral 
has avery good cleavage parallel to one of the faces of the sup- 
posed square prism—a property absent in Vesuvianite—I pre- 
pared a thin section as nearly as possible normal to the vertical 
axis of a prism, and on examining this with the polariscope, the 
absence of the interference figure proved at once that the crystal 
could not belong to the tetragonal system. On trying to break 
crystals out of the quartz matrix only portions of prisms 
could be secured ; however, these sufficed for determining by 
means of the hand-goniometer (for the reflecting goniometer the 
*Mr Cox fell into the same error, as his description of Idocrase (Vesuvianite), 
p 402, Vel. XV., Trans. N. Z. Inst., refers, according to Mr. Docherty, to the 
identical mineral. 
