CRY 



rather tender annuals in our gardens, of no ftriking 

 appearance. 



CRYPTOSTYLIS, xfi/^loc, concealed, and rl'^K, a fmall 

 /.///dr.— Brown Prodv. Nov. HoU. v. i. 317.— Clafs and 

 order, Gynandria Monandria. Nat. Ord. Orchidcce. 



Eff. Ch. Calyx-leaves and petals linear, fpreading. 

 Flower reverfed. Lip ereft, feffile, dilated, undivided ; 

 concave at the bafe, concealing the very fhort column. 

 Anther parallel to the ftigma, iiibtended at each fide by a 

 lobe of the eoliimn. 



Bulis cluftered. Leaves few, radical, ftalked, flat. 

 Floivers in a terminal fpike, dull red, fcentlefs. 



1. C. longifolia. (Malaxis fubulata ; Labill. Nov. HoU. 

 V. 2. 62. t. 212,) found at Port Jackfon, as well as on the 

 fouth coaft ; 



2. C. ovata; and 3. C. ereda ; are the only defcribed 

 fpecies. 



CRYSTAL, col. 5, 1. 19, for changed r. charged. 



CRYSTALLOGRAPHY is the fcience which treats 

 of the form and ftrufture of cryftals. (See Crystal.) 

 The beautiful fymmetrical forms, which frequently occur 

 in the deep receltes of mines or the fiffures of alpine rocks, 

 cannot fail to ftrike the moft common obferver with fur- 

 prife. Amidft the almoft infinite variety which they prefent, 

 it will be found, on a more attentive examination, that there 

 are certain definite forms which fome minerals moft fre- 

 quently affume, and which are rarely, if ever, feen in other 

 minerals. Hence we might at firft be led to infer, that 

 cryftallization depends on the definite aftion of fome gene- 

 ral law, by which the conftituent parts of each mineral 

 fpecies are invariably arranged in the fame form. When, 

 however, it is farther difcovered that, befides the prevailing 

 forms peculiar to certain minerals, the fame fpecies are not 

 unfrequcntly cryftallized in a variety of diffimilar forms, 

 and that minerals of different fpecies often prefent cryftals 

 of the fame form, we muft retraft our firft conclufion, 

 and ftiall be more difpofed to believe that the mineral king- 

 dom has not yet emerged from a chaotic ftate, or that the 

 reign of order is fubjedt to the invafion of difturbing forces, 

 the extent of which we have no means of afcertaining. 



The labours of a few enlightened and indefatigable phi- 

 lofophers have recently removed, in a great degree, the 

 obfcurlty in which this department of fcience was nivolvcd, 

 and have demonftrated that the laws by which the particles 

 of the minuteft cryftal are arranged aft with unerring pre- 

 cifion, and are not lefs regular than thofe which govern the 

 motions of the planets or the folar fyftem. 



Under the article Crystal (which fee), fome account is 

 iven of the difcoveries of Rome de Lifle, Bergmann, and 



aiiy. The latter has ably demonftrated that all the varie- 

 ties of cryftalline forms are reducible to a few fimple primi- 

 tive forms, fome one of which may be regarded as the 

 nucleus of each cryftal, however complicated its form may 

 be. The conftituent particles, or what Haiiy denominates 

 the integrant molecules, of all cryftals, may be conceived as 

 arranged in rows, and a number of thefe rows as forming 

 thin laminse or plates. When thefe laminae are parallel with 

 all the faces or planes of a cryftal, they may be removed 

 without changing the form of the cryftal ; but if the larninse 

 divide in any other direflion than that which is parallel to 

 ihc faces, a change of form will be produced by every divi- 

 fion, until at laft we obtain a nucleus which is divifible in a 

 direftion parallel to its fides. 



In the former cafe, the primitive form is the form of the 

 cryftal itfelf. Thus, if a cubic cryftal be di'/ifible only by 

 Jsminae parallel to its fix fides, we may continue diminifhing 



i 



CRY 



the magnitude of the cryftal, as long as mechanical divifwti 

 is polfible without any change of form. 



When the laminx of a cryftal divide in any other direc- 

 tion than parallel to its faces, it is called a fecondary form 

 or derivative cryftal. 



The primitive forms of all cryftals which have been 

 hitherto examined are fix. 



1. The parallelopiped, bounded by fix planes, the oppo- 

 fite planes being parallel. This includes the cube, and 

 varieties of the reftangular prifm, the oblique angular 

 prifm, and the rhomboid. 



2. The odflahedron. This is a double four-fided pyramid. 

 When the triangular faces are equilateral, it is called a 

 regular oftahedron. (PlateVll.Jig. 2"], Cryjlallography.) 

 There are, befides this, other varieties of the primitive 

 oftahedron, in which the pyramids are longer or fhorter 

 than the regular one, or have a rhomboidal bafe, or a reft- 

 angular bafe, longer in one direftion than the other. 



3. The regular tetrahedron [Plate VIL ^g. 13.) is 

 bounded by four equilateral triangles. 



4. The regular hexahedral prifm, or equiangular fix- 

 iided prifin, Jig. j. 



5. Rhomboidal dodecahedron, bounded by twelve equal 

 rhombs, ^g. 12. 



6. The pyramidal dodecahedron, confifting of tv/o fix- 

 fided pyramids joined bafe to bafe, ^g. 14. 



The primitive forms which moft frequency occur are,, 

 the parallelopiped and the oftahedron. The tetrahedron 

 and dodecahedron are very rare as primitive forms, though 

 common as the fecondary forms of cryftals. 



The divifion of fecondary cryftals by feftions in the 

 direftion of the laminoe is, in foffle minerals, effefted with 

 facility ; in others, the jdints ire indiftinft, and require the 

 cryftal to be heated and plunged into cold water to make 

 them vifible. The direftion of the laminas is frequently 

 rendered obvious by turning a mineral flowly round in the 

 funfhine, when the refleftions firom the internal parts will 

 fhew its ftrufture. Where no joints are difcoverable, Haiiy 

 determines their direftion and the form of the primitive 

 nucleus by conjefture, from the appearances offered by the 

 fecondary cryftal. 



The aftual mechanical dilTeftion of an hexahedral cryftal 

 of calcareous fpar, and the extraftion of. the primitive, is 

 reprefented in PlateW.Jigs. 17, 18, 19, 20, Cryjlallograpby, 

 and is defcribed under the article Crystal ; but the re- 

 ferences arc erroneo\illy made to Plate \.Jigs. 3, 2, 3, 4, 5. 



The primitive nucleus is reprefented Jig. 21, E A, O T, 

 G H, A K. The difcovery of it in this cryftal was firft 

 made by the abbe Haiiy in looking over the cabinet of M. 

 Defiance, a hexahedral prifm of calcareous fpar having 

 fallen from the group to which it was attached. M. De- 

 fiance made him a prefent of it. One of the corners being 

 off from the bafe, he attempted to detach fimilar corners 

 from the othrr angles, and after fome time he fucceeded in 

 bringing to view its rhomboidal nucleus. This firft fug- 

 gefted to him the theory of the ftrufture of cryftals. The 

 fituation of the primitive form, in another variety of cal- 

 careous fpar, called the dog-tooth fpar, may be feen 

 Plate W. fgu 22 and 23. This is defcribed under the 

 srticle Crystal, with the mode of extrafting the nucleus; 

 but the reference is erroneoufly made to Plate l.Jigs. 6 and 7. 

 The angles of the primitive rhomb arc invariably ioj'^5' 

 and 74° 55'. Rhomboids of calcareous fpar, indeed, oeciir 

 with different angular admeafurements ; but thefe are fe- 

 condary cryftals, and will not fplit in direftions parallel to 

 their faces- One of thefe, with the primitive nucleus, is 



reprefented 



