On Crystallography, 271 



duodecimal sulphated copper. Deciduodecimal. Ex. 

 Deciduodecimal feldspar. ' 



jc. Peripolygoval, when the prism has a great number of 

 panes. Ex. Peripolygonal tourmaline. 



y. Super composite, when the form is very much com- 

 pounded. Ex. Supercomposite tourmaline. 



rs. Antiemieahedrnl, i. e. having nine faces on two oppo- 

 site sides, is a name peculiar to a variety of the tour- 

 maline^ in which the two summits are of nine faces, 

 and the prism of twelve panes j whereas^ generally, 

 the prism is enneahedral. 



aa, Prosenneahedral, i. e. having nine faces on two adja- 

 cent parts, is another variciy of the tourmaline, ia 

 which the prism and one of the two summits have 

 each nine faces. 



II, Recurrent, when, on taking the faces of the crystal 

 by annular rows, from one extremity to the other, 

 we have two numbers, which succeed several times, 

 as 4, 8. 4, 8, 4. Ex. Recurrent oxidated tin. 



cc. Eiiuid'ifferent, when the numbers which designate the 

 faces of the prism and those of the two summits^ which 

 in this case differ from each other, form the commence- 

 ment of an arithmetical series, as 6_, 4^ 2. Ex. Equi- 

 different amphibolus. 



dd. Converge7it, when in the foregoing case the series 

 is sensibly convergent, as 15, 9, 3. Ex. Convergent 

 tourmaline. 



ee. Unequal {Impair), when the numbers which designate 

 the panes of the prism and the faces of the two sum- 

 mits, considered as different from each other, are all 

 three unequal, without being in other respects in pro- 

 gression. Ex. Unequal tourmaline. 



ff. Hyper- oxidated, i.e. aaite to excess, is a variety of 

 carbonated lime, which contains the combination of 

 two rhomboids ; the one acute, which is the inverse ; 

 the other incomparably more acute. 



gg. Spheroidal, is said of the diamond with 48 bombaled 

 faces. 



hh. Plano-convex, is the diamond with' some plane and 

 some curvilinear faces. 



3. Secondary forms considered relatively to certain facets, 

 or certain ridges, remarkable for their arrangement 

 or position. 



The crystal is called, 

 «. Alternate^ w'h^n it hasonitst\^o parts, the one supe- 

 rior 



