A new system of Crystallographic Symbols. 259 
These will serve as a specimen of his longest and shortest terms, 
and of the greater conciseness, in every instance, of the proposed 
substitutes. 
The following is the description of a modified right rhombic prism, 
taken from page 426 of the work above referred to. 
1G1 MB E (B1 H1 B2: B2 HI B/1)(B1 H3 B2 : B2 H3 B/1)P. 
4 3.1 
Translated it becomes e P e a a® w&? P. 
~ 
The following symbols describe a crystal of Boracite, the edges 
and half the angles of which are replaced, each by tangent planes. 
According to the system of the 
OL) Cy AO) 
Abbé Haiiy, its representative sign is P BAacE. 
Brooke a6 ee PB oA? 1AQ 1g) 03°, 
Mohs ue oe ete H.O.D. 
Whewell “© 2(3)1,0,0) +2(6)(41,1,0) +(4)(41,1,1). 
The proposed substitute is Pe ($a). 
The most important advantage of this system is, that the symbols 
may be applied tothe figures of crystals. It is frequently quite dif- 
ficult for the student to determine the situation of secondary planes 
relative to the primary, particularly when the form of the nucleus 
is entirely concealed. ‘The secondaries of the Rhombohedron may 
be instanced as peculiarly difficult. ‘This difficulty evidently van- 
ishes, when the figure is so lettered, that each plane may be ea- 
sily referred to its situation on the primitive form. This as has been 
already shown, will be accomplished by the proposed system. 
Even if the rate of decrement is not determined, still nearly an 
equal advantage is obtained. ‘The planes on any particular edge or 
angle, may be distinguished by numerals, thus 1é 2é 3é, &c. In 
this manner the edge or angle on which a plane is situated, and the 
plane on which it inclines, may be pointed out. 
Fig. 1, has already been explained. If it is remembered that the 
posterior planes, angles and edges have the same symbols as their 
diagonally opposites, no difficulty will appear in any part of it. 
Fig. 2. A crystal of Iron pyrites. Primitive form. Cube. 
SER 
Description. Pa? Oe cc SLES 
