20 TERMINOLOGY. . 21. 



crystallisation. The assemblage of those properties, is the 

 mineral, or the natural production itself; at least, in as 

 far as it is an object of Natural History. 



Minerals, upon which the power of crystallisation has 

 not exercised its action, are without individuality, and 

 therefore do not possess any of the properties connected 

 with this state of existence. They want unity of space ; 

 they are not single bodies, and, as such, by themselves fit 

 objects of Natural History. As mere shapeless masses, 

 with certain inherent properties, they can be considered as 

 objects of Natural History, only because they are natural 

 productions (. 4.). 



Temperature has a great influence over the power of 

 crystallisation. Several minerals, as water, fluid mercury, 

 &c. pass into the state of individuality, and become solid, 

 if the degree of temperature be sufficiently reduced ; on 

 the contrary, by an increase of temperature, hexahedral 

 silver, octahedral bismuth, &c. leave this state, and become 

 liquid, and others elastic. * For that reason, in treating of 

 Natural History, it is necessary to fix the degree of tem- 

 perature in which the productions of the mineral kingdom 

 are considered; and this is the ordinary temperature, at 

 which water is fluid, and the most fusible crystals are solid. -j- 



. 21. MINERALS DECOMPOSED AND IMPERFECTLY 

 FORMED. 



The productions of the power of crystallisation 

 continue to be objects of natural-historical conside- 

 ration, so long as they retain the properties pecu- 

 liar to them, which they have derived from the ac- 

 tion of this power. By the loss of some or of seve- 



* If the change produced on a mineral by the application 

 of heat, affects more than the mere state of aggregation, 

 the consideration of this change makes part of another sci- 

 ence, and has no reference to Natural History. 



f This is the reason why water, and not ice, has received 

 a place in the system. 



