Z I 



[468] 



Z D 



width is nearly equal to the length 

 of the body. Dr. Maniell. 



ZINC. ] (sink, Germ.) A metal of a 



ZINK. ) bluish-white colour, with a 

 fine granular fracture. Zinc was 

 not obtained in its metallic form 

 till the sixteenth century, though 

 its ores were known to the ancients, 

 and used by them in the formation 

 of their brass or bronze. It does 

 not occur native ; its most abundant 

 ore is the sulphuret, called Blende, 

 common in most veins which con- 

 tain sulphurets of iron, lead, copper, 

 &c. in every country. The structure 

 of zinc is foliated. As regards its 

 hardness, it may be easily cut with 

 the knife. Specific gravity from 

 6-9 to 7-2. It is malleable, but its 

 malleability is greatly increased by 

 heating it to a temperature of 300 

 Fahrenheit. By exposure to the 

 air it tarnishes and loses its lustre, 

 but it is but little oxidated. Uni- 

 ted with copper it forms brass. The 

 ores of zine are few. Its presence 

 may be determined by roasting the 

 ore, and then fusing it by the 

 blow-pipe on charcoal with filings 

 of pure copper. If zinc be present, 

 the copper will be converted into 

 brass. The ore called calamine is 

 a carbonate of zinc. 



ZI'PBTTJS. The name assigned by 

 Cuvier to a genus of cetacea; it 

 contains three species, and appro- 

 ximates lo the cachalots and hy- 

 peroodontes. The head differs from 

 that of the hyperoodon, in the 

 maxillary bones not forming verti- 

 cal partitions on the sides of the 

 muzzle, and in the partition behind 

 the nostrils not only rising verti- 

 cally, but also curving, so as to 

 form a kind of half cupola over 

 these cavities. Pidgeon. 



ZI'RCON. (By some the word zircon 

 is deemed of Indian origin, others 

 derive it from the French word 

 jargon, esp&ce de diamantjaune.J A 

 mineral occurring in rounded grains 

 or fragments, or in regular crystals. 



The primitive crystal of zircon is, 

 according to Haiiy, an obtuse octo- 

 hedron; the common base of the 

 pyramids is square. The measure- 

 ments, as afforded by the reflecting 

 goniometer, are 84 20' by 95 

 40'. It is harder than quartz, and 

 possesses double refraction in a 

 high degree. It is transparent, or 

 sometimes only translucent. Spe- 

 cific gravity from 4-3 to 4*7 Before 

 the blow-pipe it is infusible, but 

 loses its colour. It may be dis- 

 tinguished from garnet, idocrase, 

 staurotide, &c., by its infusibility, 

 specific gravity, and strong double 

 refraction. There are two varieties 

 of zircon, called zircon jargon and 

 zircon hyacinth. Zircon jargon 

 consists of zirconia 69, silica 26'5, 

 oxide of iron 0'5. Zircon hyacinth 

 of zirconia 70, silica 25, oxide of 

 iron 0'5 Some mineralogists divide 

 zircon into three subspecies, name- 

 ly, zirconite, hyacinth, and jargon. 

 The finest specimens are brought 

 from the island of Ceylon. It 

 occurs in primary and transition 

 rocks, but is usually obtained from 

 the sand of rivers. 



ZIRCO'NIA. An earth, when pure, 

 white and tasteless, supposed to be 

 a compound of zirconium, its me- 

 tallic basis, and oxygen. An oxide 

 of zirconium. 



ZIBCO'NITE. A subspecies of zircon, 

 consisting, according to the analy- 

 sis of Klaproth, of zirconia 69, 

 silica 26-5, oxide of iron 0'5* It 

 occurs in reddish-brown and nearly 

 opaque prismatic crystals. Itishard- 

 er than quartz, but softer than dia- 

 mond. Sp. gr. from 4'5 to 4*7. 



ZIECO'NIUM. The metallic base of 

 zircon. 



ZOANTHA'RIA The third order of the 

 class actinozoa, comprising six-star- 

 red corals, sea-anemone, beroe, &c. 



ZO'DIAC. (zodiaque, Fr. zddiaco, It. 

 zodiacus, Lat. gwdicuco?, Gr.) A 

 broad circle or region in the hea- 

 vens, remarkable, not from any thisg 



