[ 95 1 



XIV. On CnjstaUograph}/. By M. Haw. Translaiedjiom 

 the last Paris EdUion of' Ids Tra.\i6 de Mineialogie. 



[Continued from p. 09] 

 OF CRYSTALLIZATION. 



W E have been led bv observation and reasoning to ascer- 

 tain tliat minerals were composed of similar integrant mole- 

 cules. The way in which they are mechanically divided has 

 besides provexl to us, that the cause which solicited these 

 molecules to be mutually attracted, reunited them in rows 

 ■upon plartes situated in the direction of their different 

 faces. These considerations were useful for preparing the 

 development of another very remarkable result of the laws 

 of affinity, which is referred to the external configuration 

 of miTierals, and has given birth to one of the most fertile 

 branches of the science of which they are the objects. 



Such therefore is the action of these laws upon integrant 

 molecules, that, when nothing disturbs it, the assemblages 

 of these molecules are tern)inaled by plane surfaces, whence 

 result regular forms similar to those of geoiricirical solid-. 

 We have frequent examples of this regularity in the garnet, 

 topaz, emerald, carbonated lime, sulphated barytes, &c. ; 

 and in a great number of metallic substances. The sight of 

 these polyhedrons alwavs excites the surprise of a person to 

 whom they are for the first time presented, and they must 

 frequently be shown to him inerusted with their native earth 

 beibre he can believe in the geometry of nature. 



All these regular bodies have been recei\ ed under the coin- 

 mon denomination of rrj/j/a/j"*. The term cryiialiizatiori, 

 vv'hich would at first sight appear to apply onlv to the species 

 of operation from which crystals are produced, hasgeneially 

 a more extensive signification. Tt expresses in general every 

 assemblage of molecules in solid masses by the help of afiB- 

 nity. If these masses have a symmetrical aspect, they will 

 be the products of regular crystallization properly so called. 

 If their form is vague, and crainot be determined in a precise 

 manner, they will belong to confused crvstallizalion. 



The attractive forces which "solicit the molecules of a mi- 

 neral, suspended in a liquid, have a certain reference with 

 the figure of these molecules, and it is in this relation that 

 the tendency consists which the nn)lecule3 have of them- 

 selves to unite conformably to the laws of a regidar aggre- 

 gation. Bill in order that they may attain this object, they 



* The origin of thii word will be found under the article of Quartz. 



must 



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