CRY 



[118] 



CRY 



the form of the molecules of which 

 it is composed. Crystals are sym- 

 metrical forms. "It hasbeen said of 

 crystals," says the Abbe Haiiy, "that 

 they are the flowers of minerals; " 

 an observation concealing a very just 

 idea beneath the air of a comparison 

 which appears to be only ingenious. 

 The importance of their form will 

 become more evident if, in pursuing 

 our enquiries into the niceties of 

 the mechanism of structure, we 

 conceive all these crystals as the 

 assemblages of integrant molecules 

 perfectly resembling each other, 

 and subject to the laws of regular 

 arrangement. Thus although, by 

 a superficial notice of crystals, we 

 might adjudge them to be only the 

 sports of nature, a more intimate 

 acquaintance with them leads to 

 this conclusion, that the Deity, 

 whose power and wisdom prescribed 

 the unerring laws of the planetary 

 motions, has also established those, 

 which are obeyed with the same 

 fidelity, by the molecules compo- 

 sing the various substances concealed 

 in the recesses of the earth. There 

 are six primitive forms of crystals. 



1 . The regular tetrahedron, having 

 four equilateral triangles for its 

 faces. 



2. The regular cube of six squares 

 for its faces. 



3. A dodecahedron, or solid of 

 twelve faces, each being a rhombus. 



4. The octohedron, having eight 

 triangles for its faces. 



5. A six-sided prism. 



6. A parallelepiped, or a solid of 

 six faces, each two of which are 

 parallel and equal, as a cube, a 

 rhomboid, &c. Prom these six 

 primitive forms of crystals every 

 variety may be supposed to be 

 produced, by cutting away itsangles 

 or edges in various manners ; or by 

 additions supposed to be made on 

 its faces. The regularity of the 

 figure will be influenced by the 

 rapidity of the evaporation, as 



when the evaporation is hurried 

 the crystals will be confused, and 

 wanting in regularity; sometimes 

 the evaporation must be sponta- 

 neous, or not assisted by the addi- 

 tion of heat, for procuring regular 

 and large crystals. It must not be 

 supposed that every mineral crys- 

 tallizes naturally in, or can be cut 

 into, all the forms which might 

 be deduced from its primitive form ; 

 but it never occurs that the same 

 mineral is found assuming a form, 

 which cannot be shown on these 

 principles to be related to its 

 primitive, or in which primitive 

 it either is occasionally found, or 

 to which the other forms in which 

 it occurs may not be reduced. 

 Mm. and Metals. 



When bodies dissolved in any 

 fluid are separated by crystalliza- 

 tion, they are always found to 

 retain a part of the fluid. The 

 water thus retained by saline crys- 

 tals is called the water of crystalli- 

 zation. This water appears to be 

 essential to the transparent crys- 

 talline form of salts." Most salts 

 may be deprived of their water of 

 crystallization by heat ; some lose 

 it in the common temperature of 

 the atmosphere, and fall into a 

 pulverulent mass ; others attract 

 moisture so strongly that they, 

 from exposure to the atmosphere, 

 deliquesce. 



CRY'STALLINE HUMOUR. } (KpvaTa\ivo<s t 

 CRY'STALLINE LENS. j Gr. crystal- 

 linus, Lat.) A solid body of a 

 lenticular form, being a part of the 

 eye. It appears most absurd ever 

 to have given to this solid body the 

 name of humour. The crystalline 

 lens is situated behind the aqueous 

 humour, opposite to the pupil, and 

 its posterior portion is received into 

 a depression on the fore-part of 

 the vitreous humour. It has two 

 convex surfaces, like a common 

 lens, the anterior being the less 

 convex ; the two being formed of 



