HORNBLENDE HORNEMANN. 



talline particles, and of its exceedingly diversified 

 colours, thus giving rise to almost numberless 

 varieties, many of which have obtained distinct ap- 

 pellations. The primitive form of the species is an 

 oblique rhombic prism of 124 30' and 55 30', in 

 which the terminal planes are inclined to the obtuse 

 lateral edges, under angles of 105 and 75. The 

 former planes are easily developed, by cleavage 

 from its crystals and crystalline masses ; but the lat- 

 ter have never been obtained in this* way, having 

 been inferred from calculation. The crystals of 

 hornblende are generally long, and destitute of re- 

 gular terminations ; they are often deeply striated 

 longitJdinally, and much disposed to intersect each 

 other, sometimes in such a manner as to give rise to 

 a sheaf-like or to a stellular composition. Perfectly 

 regular, implanted crystals do occur occasionally; 

 and these present, for the most part, the following 

 shapes : six-sided prisms, from the truncation of the 

 acute lateral edges of the prism, acuminated by four 

 planes, corresponding either to the lateral edges or 

 to the lateral faces of the prism ; the same with an 

 acuin ination of three planes ; the same with dihedral 

 summits ; and the primitive form with dihedral ter- 

 minations, of which the faces correspond to acute 

 edges of the prism. The massive varieties frequent- 

 ly offer a granular structure, in which the individuals 

 are of various sizes, and strongly coherent, often with 

 a tendency to a slaty fracture ; more commonly, 

 however, the composition of massive varieties is co- 

 lumnar, the individuals being sometimes very long, 

 parallel, or diverging, and, when delicate, producing 

 a silky lustre. The lustre of hornblende is vitreous, 

 inclining to pearly, upon the faces of cleavage, in 

 the varieties possessing pale colours. Colour, vari- 

 ous shades of green, often inclining to brown, white, 

 and black, with every intermediate shade ; nearly 

 transparent in some varieties ; in others opaque ; 

 Vittle ; hardness about the same with feldspar ; 

 specific gravity, 3.00. Three varieties, analyzed by 

 Bonsdorf, gave the following results : 



A white 

 Variety. 

 60.31 

 24.2 

 13.66 

 0.26 

 0.15 

 0.00 

 0.94 

 0.10 



A green 

 fiiriety. 

 46.26 

 19.03 

 13.96 

 11.48 



3.43 



9.36 



1.60 



1.04 



A black 

 Variety. 



45.69 



18.79 



1H.85 



12.18 

 7.32 



OJN 



1.50 . 

 O.OJ 



Silex, 

 Magnesia, 

 Lime, 

 Aluminp, 

 Protoxide of iron, 



do. of manganese, 

 Fluoric acid, 

 Water and foreign > 



substances, j 



Of those varieties of the present species which have 

 obtained distinct names, and which, in some systems 

 of mineralogy, have even been regarded as forming 

 separate species, the following are the most remarka- 

 ble, viz., hornblende, tremolite, actynolite, and cer- 

 tain kinds of asbestos. Hornblende differs from the 

 rest principally by its dark, blackish, or greenish 

 colours, and is divided into three sub-varieties, 

 basaltic hornblende, common hornblende, and horn- 

 blende slate. The first consists of black and perfect- 

 ly-cleavable crystals, which are always found imbedded 

 in basaltic or volcanic rocks ; the second refers to 

 imbedded crystals of various colours, but always of 

 dark shades, and in which cleavage is less easily 

 obtained ; it includes, besides, all massive, granular, 

 or columnar varieties, except such as are black, 

 easily cleavable, and of a shining lustre, which have 

 been distinguished by the name of carinthin. Horn- 

 blende slate comprehends such varieties as consist of 

 minute and closely-aggregated particles, united in 

 such a manner as to produce a slaty fracture. Tre- 

 molite consists of the pale green, gray, bluish, and 

 white varieties, and has been subdivided into com- 

 mon, glassy, asbestiform and granular tremolite. 

 The first occurs in crystals, rarely with perfect ter- 



minations, and in massive varieties ; the second in 

 columnar compositions, or coarsely fibrous, with a 

 high degree of transparency ; the third refers to 

 very thin or capillary crystals ; and the fourth con- 

 sists of granular particles. The varieties of actyno- 

 lite differ from those of tremolite by their deep (often 

 grass-green) colours. The asbestiform tremolite and 

 asbestiform actynolite form a passage into asbestos, 

 which term is applied not only to minute columnar, 

 and variously-interwoven individuals of this species, 

 but to those also of augite or pyroxene, and may be 

 said to denote rather a peculiar state of aggregation 

 in these species than the substance of a distinct mine- 

 ral. (For an account of the varieties of asbestos, see 

 Asbestos.) The best crystals of basaltic hornblende 

 come from near Teysing and Teplitz, in Bohemia. 

 Common hornblende abounds at Arendal, and other 

 places in Norway and Sweden ; a light greenish 

 variety, imbedded in granular limestone, at Pargas, 

 in Finland, has received the name of pargasite. 

 The varieties of actynolite and tremolite abound in 

 numerous places in Europe ; the former occurring in 

 talcose slate, and the latter in limestone and dolo- 

 mite rocks. In America this species is also widely 

 disseminated. 



HORN-BOOK is a copy of the alphabet, set in a 

 frame and covered with a thin plate of horn, to pre- 

 vent the paper from being thumbed to pieces by the 

 children who were made to study it. It is now 

 almost, if not quite, antiquated, as an instrument of 

 elementary education. 



HORNECK, OTTOCAR of, one of the oldest histor- 

 ians in the German language, lived in the latter half 

 of the thirteenth and the beginning of the fourteenth 

 century. His native country was Stiria, where his 

 family castle, Horneck, is still to be found. He was 

 instructed in the art of a minnesinger by Conrad o> 

 Rotenburg. He died after the decline of the Hohen- 

 staufen, when the golden age of chivalric poetry 

 was past. After having been present at the battle 

 of Weidenbach, and accompanied Rodolph of Haps- 

 burg to Bohemia, he returned to his native country, 

 which was delivered from the Bohemian yoke, and 

 enjoyed the favour of the Stirian governor, Otho of 

 Liechtenstein, who resided in the castle at Gratz. 

 He employed his talents in writing and rhyming on 

 historical subjects, for which the German prose was 

 not yet adapted. About the year 1280, he composed 

 a work on the great empires of the earth, which con- 

 cluded with the death of the emperor Frederic II., 

 and is still extant in manuscript, at Vienna. Being 

 encouraged to note down the important events of his 

 own time, he wrote a chronicle, consisting of more 

 than 83,000 verses, which the Benedictine friar Pez, 

 in 1745, published as the third folio volume of his 

 Scriptores Rerum Austria. It extends from the death 

 of Manfred to the emperor Henry VII., and is there- 

 fore important as illustrative of the history of Ro- 

 dolph and Ottocar, Adolphus of Nassau, and Albert 

 of Austria. It is rich in remarkable events, which 

 the author witnessed, in portraits of eminent men 

 whom he had known, and in description of festivals, 

 tournaments, and battles, at part of which he was 

 himself present. See the Aus und Uber Ottokars von 

 Horneck Reimchronik, by Th. Schacht, Mentz, 1821. 



HORNEMANN, FREDERIC CONRAD, a celebrated 

 traveller, was born in 1772, at Hildesheim, studied 

 theology at Gottingen, and received an appointment 

 in Hanover. An ardent desire to visit the interior of 

 Africa, induced him, in 1795, to request Blumenbach, 

 the famous naturalist in Gottingen, to recommend 

 him to the African society in London. After having 

 fully convinced himself of the great zeal and capacity 

 of the young aspirant, Blumenbach wrote to Sir 

 Joseph Banks, and Hornemann's proposal was ac- 



