i 4 8 On Cnjstallographtf, 



11. Every letter, whether large or small, marked with a 

 cypher which has a zero after it, shows that the decrement 

 indicated by this cypher is null on the particular angle or 

 edije to which this letter refers. 



We have omitted the applications which would be neces- 

 sary for understanding these rules, if they had been pre 

 sented on our first setting out. These applications are 

 found already in the detailed explanation, which we have 

 previously given, of the principles of the system, and the 

 perusal of which is presumed to hare preceded that of 

 these same rules. 



OF INDETERMINABLE CRYSTALLIZATION, 



When the crystalline molecules disseminated in a liqiiid 

 experience obstacles which affect their tendency to reunite 

 in conformity to the laws of their mutual affinity, the 

 forms which result from their aggregation have no longer 

 that regularity which belongs to an exact and precise deter- 

 mination. Their ridges are obliterated, their faces are 

 curved, tlseir pyramids are sharpened. Hence the crystals 

 called lenticular, or which imitate the form of a lentil ; 

 cylindroids^ the prism of which is rounded off^ acicular, 

 or similar to needles ; Sec. 



If a multitude of small indeterminable crystals are so in-- 

 timately connected with each other that they form only 

 one body, we then consider this body as a particular being, 

 and hence the substances which we call striated, fibrous, 

 he, and which are formed by the junction of an infinite 

 number of crystalline needles, sometimes parallel, some- 

 times divergent, and at other limes crossing; in different di- 



rections. 



Lastly, The appellation amorphous hs^shetn given to sub- 

 stances which present, as it were, the last degree of con- 

 fused crystallization, and the vague and indefinable form 

 of which is, as it were, mzite to the eye of the observer. 



Of CoNCR.ETfONS. — ^The formation of the bodies which 

 we have hitherto mentioned, particularly of crystals pro- 

 perly so called, essentially depends on two conditions only : 

 one of which is, that the molecules of these bodies should 

 be in the state of integrant molecules ; and the other, that 

 they should be kept in suspension in a liquid capable of 

 abandoning them to the attraction which solicits them to- 

 wards each other. In short, every thing is regarded as 

 passing in the same manner as if, the force of gravity being 

 null, the liquid was not coerced by the sides of any sur- 

 rounding waiter^ and as if the crystal iiself remained iso- 

 lated 



