H I P 



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H O R 



HI'PPURITE. A fossil bivalve, having an 

 under shell of great depth, and of a coni- 

 cal form, with a flat lid, or operculum. 

 This genus is believed to be wholly ex- 

 tinct. The operculum is sometimes con- 

 vex, but generally it is concave. The 

 particular economy of the inhabitant of 

 this shell is not known. Lamarck has 

 placed the hippurite among his chambered 

 cephalopoda. Specimens of the upper 

 chamber of hippurites have lately been 

 found in the chalk, near Lewes. Dr. 

 Mantell has named a species there dis- 

 covered Hippurites Mortoni, after Dr. 

 Morton, Secretary to the Academy of 

 Natural Sciences of Philadelphia. 



HIRSU'TE. (hirsutus, Lat.) Hairy ; rough ; 

 shaggy ; beset with strong hairs. 



HIRSU'TENESS. Hairiness ; shagginess. 



HISI'NGERTTE. A mineral of a dark co- 

 lour, occurring massive, found in the 

 cavities of calcareous spar. 



HI'SPED. ) (hispidus, Lat.) Hairy ; beset 



HI'SPID. $ with strong bristles. 



HOG-TOOTH SPAR. A dodecahedral variety 

 of calcareous spar. The Matastatique of 

 Hatiy. 



HOLOPTY'CHUS. A genus of fossil sauroid 

 fishes, discovered in the coal formation. 



HOLOPTY'CHUS HIBBERTI. A species of 

 holoptychus named after Dr. Hibbert, 

 and found by him in the limestone of 

 Burdie House. 



HOLOTHU'RIA. A zoophyte belonging to 

 the order Pedicellata, class Echinoder- 

 mata. The holothuria is covered with a 

 thick coriaceous skin, which, by means of 

 longitudinal and circular bands of mus- 

 cular fibres, the animal can shorten or 

 lengthen at pleasure. The body is ob- 

 long, and open at each end ; numerous 

 tentacula surround the mouth. There are 

 many species. 



HO'LMITE. A mineral, a variety of car- 

 bonate of lime, named after Mr. Holme, 

 who analysed it. Its constituents are 

 lime, carbonic acid, oxide of iron, silica, 

 alumina, and water. 



HOMOGENEITY, (homogeneite, Fr. omo- 

 ffeneita, It.) Of the same nature ; having 

 the same nature throughout. 



HOMOGE'NEAL. ^ (ofjLoytvrjQ, Gr. homo- 



HOMOGE'NEOUS. $ gene, Fr. omogeneo, 

 It.) Similitude of kind ; sameness of 

 nature. 



HOMO'LOGOUS. (fiomologue,Yr. omologo,lt. 

 o/i6Xoyoc, Gr. ) Having the same manner 

 or proportions. 



HONE, (keen, Sax.) Whetstone slate. 

 A variety of talcy slate, containing parti- 

 cles of quartz : when these particles are 

 exceedingly minute, and the slate pos- 

 sesses a certain degree of hardness with a 

 uniform consistence, it yields hones of the 

 best quality. Kirwan gave to this mine- 



ral the name novaculite, from novacula, 

 the Latin for a razor. 



HO'NEY -STONE. Pyramidal mellite. The 

 Honigstein of Werner ; Mellite of Haiiy 

 and Brongniart ; and Mellilite of Kirwan. 

 It is pyramidal, its primitive form being 

 a pyramid of 118 4' and 93 22'. It was 

 first discovered in Thuringia, between 

 the layers of wood-coal. It is of a honey- 

 yellow colour, sometimes a little tinged 

 with brown. Transparency considerable. 

 When heated it whitens, and in the open 

 air burns without being sensibly charred. 

 It yields neither flame, smoke, nor odour. 

 It is composed of alumina, water, and an 

 acid to which Klaproth gave the name of 

 mellitic acid : the latter constitutes 46 per 

 cent, of the whole. It differs from amber 

 in its weak electricity, double refraction, 

 and chemical character. 



HORIZO'NTAL. (horizontal, Fr. orizzon- 

 tale, It.) Parallel to the horizon ; flat. 



HORIZONTA'LITY. Flatness ; the state of 

 being horizontal. 



HORIZO'NTALLY. In a direction parallel to 

 the horizon. 



HO'RNBLENDE. The amphibole of Haiiy. 

 A mineral of a black or dark green 

 colour, often intermixed ; heavier than 

 either quartz or felspar, but less hard, 

 its specific gravity being between 3 '15 

 to 3*38. It enters largely into the com- 

 position, and forms a constituent part of 

 several of the trap rocks, and appears to 

 connect the primary with the volcanic. 

 When breathed on, it yields a peculiar 

 bitter smell. Before the blow-pipe it 

 melts easily into a black or grayish- 

 black, glass. There are many varieties 

 of hornblende, known as carinthine, tre- 

 molite, actynolite, calamite, amianthus, 

 &c. &c. The constituents of horn- 

 blende are, silica 45*60, magnesia 18*50, 

 lime 14, alumina 1'18, protoxide of iron 

 7'50, fluoric acid 1*50. Its colours are 

 produced by the oxides of chrome and 

 iron. Massive hornblende is generally 

 coarsely granular and lamellar ; when 

 intermixed with felspar in large lamellar 

 grains, it forms sienite. This very com- 

 mon mineral may, generally, be easily 

 recognized. Though sometimes in regu- 

 lar and distinct crystals, it is more com- 

 monly the result of a confused crystal- 

 lization, and appears in masses composed 

 of laminae, acicular crystals, or fibres 

 variously aggregated. Though inferior 

 to schorl in hardness, hornblende usually 

 will scratch glass, and, though with diffi- 

 culty, will yield sparks with steel. Its 

 laminated structure, its inferior hardness, 

 and its inability of becoming electric by 

 heat, distinguish it from schorl. It is 

 less hard and more easily fusible than 

 augite. It differs from epidote in hard- 



