CALCITES OF NEW YORK Byut 
is that it provides a symbol of comparatively more simple indexes for the 
more important forms. Its principal disadvantage compared with the 
Bravais system consists in the failure of the Miller indexes to express the 
zonal relations to be discussed on page 33. 
Lévy’s system of symbols. The notation of A. Lévy! which is based 
upon the well known principle of the Abbé Hatty, is still used by French 
crystallographers. To develop the symbols of Lévy assume the unit 
rhombohedron lettered as in figure 18, that is the capital letters A, B, D 
and E are disposed on the angles and edges of the rhombohedron as 
follows: | 
The terminal solid angles are denoted by A 
The terminal or polar edges are denoted by B 
The lateral edges are denoted by D 
The lateral solid angles are denoted by E 
It is evident that the planes of every crystal form of calcite will truncate 
or bevel one of the elements. The Lévy symbol consists of one or more 
lower case letters corresponding to the edges or angle of the rhombohedron 
intersected by the plane of the form in combination with the rhombohedron, 
these letters being followed by figures placed as exponents which figures 
express the relative length of the edge or edges intercepted by the plane. 
The basal pinacoid shown in figure 2 which truncates the angle A and which 
intercepts equally the edges B is designated in the Lévy system by the 
symbol a‘. Similarly the prism of the first order [fig. 3] is designated by 
e’ and the prism of the second order [fig. 4] which bevels the edge D is 
designated by d'. Scalenohedrons having for the rhombohedron of the 
middle edges the unit rhombohedron, also bevel the edges D but since their 
initial planes intercept the edge B above at a greater distance than the edge 
B below the exponents of d in the Lévy symbols for these forms which 
express this ratio will be greater than one. Thus for the scalenohedron 
R3 (Naumann) the Lévy symbol is d’ since the initial plane of R38 intercepts 
‘Lévy, A. Description d’une collection de mineraux formée par M. H. Heuland. 
London 1837. 
