ISO 
Mr Levy on Euclase. 
the primitive form, because they are always brilliant, and free 
from striae, whilst it is just the reverse with all the other planes 
in the same direction ; and I have determined the base by as- 
suming, that the faces b , marked V, are the result of a decre- 
ment by one row upon the edges b of the primitive. This sup- 
position gives simpler signs for the rest of the modifications, 
than several others I have tried. I have found the incidence 
of m on m 114°.50', that of b' on m 91°.35', and that of the two 
faces b' 143°.50'. By means of these data, and the supposition 
mentioned above, I have calculated the dimensions of the primi- 
tive ; and from the parallelism of edges, where it was sufficient, 
or from observed incidences where it was not, I have calculated 
the other modifications. 
Fig. 2. represents a crystal of a pale green, in which the faces 
i"" = (b 3 dj g 1 ) are very dull, and, consequently, this sign is 
only given as an approximation. 
Fig. 3. represents a very well defined crystal, of a still paler 
green, and especially remarkable, by shewing both summits. 
Fig. 4. represents a remarkably well defined crystal, nearly 
white. 
Fig. 5. is the crystal which belonged to the Marquis de Dree’s 
collection, and which has been mentioned in almost every trea- 
tise on mineralogy. The small triangular faces i' are dull, and 
I could not determine them either by parallelism of edges, or 
by measurements. 
Dimensions of the Primitive Form and Table of the Modifi- 
cations. 
m,m- 11 4°. 50'. P, m = 118°. 46'. b:h::l: .5233. 
Plane angle of the base, ~ 104°. 12'. 
Plane angle of the later faces, — 110°.32'. 
Modification g 1 
* n,g l = 
122°. 35' 
?>,<?'= 90° 
Mod. 
h 1 
m, h 1 = 
147°. 25' 
g\h 1 = 90° 
Mod. 
¥ 
m , ¥ — 
165°. 8' 
g\ h s : 107°.43' 
Mod. 
h 5 
m, h 5 — 
170°.30' 
g i ,h 5 = 113°.20' 
Mod. 
b l 
m, b 1 = 
91°.35' 
b\ b 1 = 143°.. 50' 
Mod. 
H 
m,b\~ 
139°.44' 
bl, bl = 105358' 
Mod. 
d l 
712, d 1 = 
1 38°.23' 
d\ d 1 = 156M0' 
Mod. 
a % 
m,a Q — 
131°. 38' 
a Q ,a e = 151°.47' 
Mod. 
m> a, x = 
154°.32' 
a i ,a i = 130°.15' 
