SiO On Crystallography* 



Wc say irhhomhoidal in the same manner. Ejc^ 

 Trirhoniboidal carbonatLci lime. 



«i. Bfform, triform, when it contains a combination of 

 two or three remarkable forms ; such as the cube, the 

 rhoniboid, the octahedron, the regular hexahedral 

 prism, Sec. Ex. Triform su]|>hated alumine. 



n, CuhO'Octahedraly cuho'dodt'cakedral, cubo-tetrakedral, 

 &c., when it contains a combination of the two forms 

 indicated by these expressions. Ex. Cubo -octahedral 

 fluated lime, cubo^dodecahcdral sulphurated iron, 

 cubo-tetrahedral gray copper. 



h. Trapezia?ii when its lateral surface is composed of tra- 

 pezia situated on two rows between two bases, Ex. 

 Trapezian sulphated barytes. 



p. Diieirahed/al, \.G. iw'ict telrahedral, when its form i* 

 that of a tetrahedral prism with dihedral summits, 

 Ex. Ditetrahedral grammatite. 



q. Diliexahedral, when it forms a hexahedral prism \vitb 

 trihedral summits. Ex. Dihexahedral feldspar. 



We say in the same manner, diocialiedral, d/de- 

 cahedralf didodecakedraL Ex, Dioctahedral topaz, di- 

 decahedral feldspar, didodecahedral phosphated lime. 



r, Trihexahedral, ietrahexalwdral, pentahexahedral, hepta- 

 hexahedral^ when its surface is composed of three, 

 lour, five, seven rows of facets disposed in sixes the 

 one above the other. Ex. Trihexahedral nitrated 

 potash, pentahexahedral quartz, heptahexahedral ni- 

 trated potash. 



We also say in the same manner, iridodecahedraL 

 Ex. Tridodecahcdral sulphurated antimoniated silver. 

 — Trloctahedral. Ex. Trioctahedral sulphated lead. 



Sy B'lgeminated, when it presents a combination of four 

 forms, which, taken by twos, are of the same species. 

 Ex. Bigeminated carbonated lime. 



t. Amphikexahcdral, i.e. hexahedral in two ways, when 

 by taking the faces according to two diflfercnt direc- 

 tions, we have two hexahedral contours. Ex. Am- 

 phihexahedral axinite. 



a., Scxdec'irnal, when the faces which belong to the prism 



or to the middle part, and those which belong to the 



two summits, are the former six in number, and the 



latter ten in number, or vice versa. Ex. Sexdecimal 



feldspar. 



In the same manner we say octodechncL Ex. Oc- 

 todecimal feldspar. ScxduodecimaL Ex. Sexduode- 

 ciinal Ctjrbonaled lime. Octodaodeclmal. Ex. Ocio- 



* duodecimal 



