J 7 2 On Crys lallog rap hy . 



rior and the oihcr inferior, faces which alternate 

 among each other, but which correspond on both sides. 

 Ex. Ahernate quartz. 

 Bisaltermite^ when in the foregoing case the alternation 

 takes place, not only among the faces of one and the 

 same part, but also among those of the two parts. 

 Ex. Bisalternate carbonated iin)e, bisalternate quartz. 

 Biiisalternate, when there are on both sides two orders 

 of bisalternate facets. Ex. BibisaUcrnate sulphurated 

 mercury. 

 I, Annulary, when a, hexahedral prism has six marginal 

 facets ranged in form of a ring around each base. Ex. 

 Annulary emerald. 



We say the same of an octahedral prism with eight 

 marginal facets around bases. Ex. Annular oxidated 

 tin. 



c. Monastic, when a prism of any given number of panes 



has, in the contour of each base, a row of facets in 

 number diflerent from that of the panes, and which 

 may be all marginal, or some marginal and others an- 

 gular. Ex. Monosiic topaz. 



Dislic, when in the same case there are two rows of 

 facets around each base. Ex. Di^tic topaz. 



Siibdistic, when among the facets arranged on one and 

 the same row around each base, two are surmounted 



. each by a new facet, which is as it were the rudiment 

 of a second row. Ex. Subdistic peridot. 



d. Plagt/iedral, when the crystal has facets situated in a 



slanting direction. Ex. Plagihedral quartz, plagihe- 

 dral zircon. 



e. Dissimilar, when two rows of facets, situated the one 



above the other, towards each sunnnit, have a defect 

 in svmmetry. Ex. Dissimilar topaz. 



f. Squared {tncadrt)^ when it has facets which form kinds 



of squares around faces of a simpler form already ex- 

 isting; in ttie same species. Ex. Squared fluated lime. 



g. Slighfly promintui [proyniiiuie), when it has ridges 



which form a very slight eminence. P^x. Slightly 

 prominent sulphated lime. 



h. Zonnry, when it has around its middle part a row of 

 facets, which form a kind of zone. Ex. Zonary car- 

 bonated lime. 



i. Jpophamms, i.e. »??</«?/<?>/, when certain facets or certain 

 ridges i)resent some indication useful for ascertaining 

 the position of the nucleus, which would otherwise be 

 difficult to find out, or even to determine, either in 



point 



