1012 CUBE ORE 



CROTTLES. A name given to certain lichens in Scotland which fire usod for 

 dyeing woollen stuffs brown. 



CROWBERRY. The berries of Empctrum nigrum, eaten in tho north of 

 Europe, and used in Greenland in the preparation of a fermented beverage. 



CROWN GLASS. See GLASS. 



CRUCIBLES (Creu-sets, Fr. ; Schmelztiegel, Ger.) are small conical vessels, 

 narrower at the bottom than the mouth, for reducing ores in assaying by the dry 

 way, for fusing mixtures of earthy and other substances, for melting motals, and 

 compounding metallic alloys. They ought to be refractory in tho strongest heats, not 

 ivudily acted upon by the substances ignited in them, not porous to liquids, and 

 capable of bearing considerable alternations of temperature without cracking; on 

 which account they should not be made too thick. See ASSAY ; MELTING POTS. 



CRUSHING AND GRINDING MACHINERY. See GRINDING AND C HUSH - . 



ING MACHINERY, under DRESSING OF OSES. 



CRYOIiITE. (Kryolith, Eisstein, Ger.) This mineral derives its name from 

 xpvos, ice, from the circumstance of its being fusible in the flame of a candle. It is 

 a double fluoride of aluminium and sodium, represented by tho formula APF S + 3NaF 

 (AT-F fi .6M'aX 1 ), which corresponds to aluminium 13'00 ; sodium 32'8 ; fluorine 54 - 2 

 per cent. Tho mineral usually occurs in cleavable masses of snow-white colour, 

 having a specific gravity of about 3. Cryolite is found only at Evigtok, in Arksut- 

 fiord in West Greenland, where it forms a large deposit in gneiss, associated with 

 galena, pyrites, and spathic iron ore. It is now obtained in large quantities, and is used 

 in the preparation of sulphate of alumina and alum; it has also been used in Germany 

 in the manufacture of soda and soap, and of late has found a new application in 

 America for the production of cryolite glass. Tho mineral is also employed in the 

 manufacture of aluminium, and was at one time the chief source of the metal. See 

 ALUMINIUM. 



CRYOLITE GLASS. At Pittsburg in Pennsylvania an opaque milk-white 

 glass resembling porcelain is made with cryolite. This glass may be obtained by 

 melting together the following ingredients : silica, 67'19 ; cryolite, 23'84 ; and oxide 

 of zinc, 8 - 97 per cent. 



CRYPTIIJINE, C 22 H"N (C'^^w). A volatile base homologous with chinoline, 

 found by Greville Williams in the less volatile portion of coal-tar. 



CRYSTAL. A crystal is a body which has assumed a certain geometric form. 

 It is produced by nature, and may be obtained by art. 



The ancients believed quartz to be water converted into a sblid by intense cold, and 

 hence they called that mineral crystal from Kp{iffTa\\os, ice. This belief still lingers, 

 many persons thinking that rock crystal is, in fact, congealed water. The term crystal 

 is now applied to all solid bodies which assume certain regular forms. A crystal is 

 any solid bounded by plane surfaces symmetrically arranged. Each mineral has its 

 own mode of crystallisation, by which it may be distinguished, and also its own pecu- 

 liarity of internal structure. 



We may have a mineral in a considerable variety of external forms, as pyrites, in 

 cubes, octahedrons, dodecahedrons, &c. ; but these are all related to a single type 

 the cube. Thus galena, whatever external form it may assume, has an internal 

 cubical structure. Fluor-spar, usually occurring in cubical forms, may be cleaved 

 into a regular octahedron. A little reflection will enable the student to see that 

 nature in her simple arrangements maintains an unvarying internal type, upon which 

 she builds up her varying and beautiful geometric forms. There are certain imagi- 

 nary lines which are called the axes of the crystal : these may be 



llectangular and equal, as in the cube. 



Rectangular and one unequal, as in the right square prism. 



llectangular and three unequal, as in the right rectangular prism. 



The three axes unequal, vertical inclined to one of the lateral, at right angles to the 

 other, two lateral at right angles with one another, as in the oblique rhombic prism. 



The three axes unequal and all the intersections oblique, as in the doubly oblique 

 prism. 



Three equal lateral axes intersecting at angles of 60 and a vertical axis of varying 

 length at right angles with tJie lateral, as in the hexagonal prism. 



Upon these simple arrangements of tho axial lines all the crystalline forms depend. 

 the particles of matter arranging themselves around these axes according to some law 

 of polarity which has not yet been developed. For an outline of Crystallography, see 

 Watts's ' Dictionary of Chemistry.' 



CRYSTAL. A name given to flint glass. See FLINT GLASS. 



CUBE ORE. ( Wiirfelers, Ger.) A common name for Pharmacosidcrite : a hydrous 

 arsenate of sesquioxide of iron, occurring in some of the Cornish copper-mines, and in 

 Saxony, in the form of small cubes, generally of a green colour. 



