TOPAZ-TORA. 



Pyr"plivMli(e. P.cnitr. 



-V 74 51*00 



34-36 38'43 



7'77 --1 



long, and parallel, and their faces of composition 

 longitudinally streaked. Two varieties of tnpa/ 

 have, without sufficient reason, been treated as 

 forming separate species, viz. pyrophysalite and pi/c- 

 nitc. The first of these occurs in large individuals 

 of a pale greenish-gray colour, and faint translu- 

 cency, imbedded in round masses, in a granite com- 

 piiM-d of white quartz, feldspar and mica, at Fahliin 

 and Fmbo in Sweden. The pycnite (schorlite) con- 

 sists of thin and straight columnar particles of com- 

 position, forming masses of considerable size, in a 

 rock composed of quartz and mica, nt Altenberg in 

 Saxony, in Siberia, and at Kongsberg in Norway. 

 But these varieties are united with common topaz 

 by transitions, which render their distinction often 

 impossible. Topaz consists, according to Berzelius, 

 of 



Tepu. 



Alumina, . . 57-45 



v il.-\. . . 34-24 



Fluoric noid, . 7'75 

 In a strong heat, the faces of crystallization, but 

 not those of cleavage, arc covered with small blis- 

 ters, which, however, immediately crack. With bo- 

 rax it melts slowly into a transparent glass. Its pow- 

 der colours the tincture of violets green. Those crys- 

 tals which possess different faces of crystallization 

 on opposite ends, acquire different kinds of electri- 

 city, on being heated; by friction it acquires positive 

 electricity. Topaz enters into the composition of se- 

 veral granitic rocks ; thus it forms, with quartz and 

 tourmaline, the topaz rock of Saxony, and is found 

 crystallized in its drusy cavities. It occurs, also, in 

 irregular beds, either with quartz and mica, like the 

 variety called pycnite, or it is found in veins and beds 

 in gneiss, mica-slate, clay-slate, and porphyry, along 

 with tin ore, wolfram, fluor, beryl, quartz, &o. It 

 is met with besides in the alluvial deposits of rivers, 

 along with other gems. Among the varieties of 

 topaz, employed in jewelry, are the following, which 

 depend upon their colours : 1. colourless, or white to- 

 paz (called novi mina~) ; its localities are New Hol- 

 land, Brazil, and the Ural mountains, and it com- 

 monly occurs in rolled pebbles ; 2. blue topaz, or 

 Oriental aqua-marine ; it comes from Siberia, and, of 

 late, has been found in Brazil ; 3. straw yellow topaz, 

 found in the Urals, and at Mucla in Asia Minor ; 4. 

 wine-yellow topaz, found in Saxony ; 5. brownish- 

 yellow topaz, from Brazil ; 6. pink-coloured topaz, 

 which is produced by heating, in a sand bath, to a 

 moderate degree, the deep-yellow Brazilian crystals. 

 The topaz is now too abundant in nature to com- 

 mand the extravagant prices of some other gems ; 

 for it is not only afforded plentifully in Brazil, but 

 it is found also in the tin mines of Saxony, Bohemia 

 and Cornwall ; also at Cairngorm in Aberdeenshire, 

 where pieces of very extraordinary dimensions have 

 been found possessed of very rich brownish tints. 

 The mountains of Altai and the Urals produce an 

 immense quantity in like manner, of this gem ; and 

 large bags of pebbles and loose crystals are frequently 

 brought from Brazil and New Holland. The United 

 States have as yet furnished but a single locality of 

 topaz ; it exists at Munroe in Connecticut, and oc- 

 curs in a vein about one foot wide, accompanied by 

 fluor, mica, and quartz. The vein traverses gneiss. 

 It occurs both crystallized and massive ; but the 

 crystals are rarely transparent. They vary in size 

 from many pounds weight down to that of a few 

 grains. Their prevailing colour is white. 



TOPHET, OK HINNOM; a valley near Jerusa- 

 lem, called, also, in the New Testament, Gehenna 

 (rn,), by corruption from the Hebrew Ge (val- 



ley), and Hinnom. It was infamous as a spot in 

 which the Jews passed their children through the 



fire to Moloch, god of the Am lites. The name 



Tophet is from the Hebrew word for drum, bci-;iu>c 

 a drum was used to drown the cries of the victims. 

 The valley was watered by the brooks Kedron and 

 Silo, mi, and being a fertile and agreeable spot, was 

 at one time occupied with gardens, whence the pro- 

 priety of Milton's expression: 



The plna*mit. vnlloy of Ilinuom, Tophet thence, 

 And black QetMOM c iilli-d. 



It was, at a later period, shunned as unclean, by the 

 Jews, and made the receptacle of the filth of the 

 city. The Aceldama (q. v.) was adjoining it. The 

 (u'lii'ima of the New Testament is rendered hell in 

 the English version ; and with the Mohammedan.-> it 

 is the name of one of the circles of the fiery pit. 



TOPICAL, in medicine (from Tares, place), is 

 used of remedies applied externally to the suffering 

 part, and intended to have an effect there only, such 

 as ointments, cataplasms, &c. 



TOPICS. The ancient Greek and Roman teach- 

 ers of rhetoric designated by this word (derived 

 from Tetrei, place, passage) a systematic representa- 

 tion of certain general notions and proposition?, 

 which, as they thought, might be advantageously 

 used, by public speakers, in the selection and inven- 

 tion of arguments. They distinguished the loci 

 argumentorum (sources of proofs), and the loci com- 

 munes (common places). Under the first, they 

 comprised general notions, from which the orator 

 might deduce proofs by comparing with them the 

 case in question, e. g. the similar, the dissimilar, 

 the opposite, cause and effect, genus and species, 

 &c. Common places were general propositions, 

 formed by transferring the proofs, which were de- 

 duced from the loci argumentorum, and applicable 

 only to the special case, again to the genus. Such 

 a common place, in the forensic discourses of the 

 ancients, was the position, All legal causes are so 

 far of equal importance as the question is, What is 

 just and right ? Compare Aristotle's Rhetoric (lib. 

 i., particularly chap. 2, 3) ; the author of the rhe- 

 torical work Ad Herennium (1st, 2d, 3d book) ; 

 Cicero De Inventions (lib. i., chap. 6 15; chap. 

 24 52 ; and lib. ii.) ; Cicero's Topica and Parti- 

 tiones Oratories (chap. 1, 2, 3, 9 15) ; also De 

 Oratore (lib. ii., chap. 30 et seq.) ; Quintilian's 

 work Institutions Oratoria (lib. v.). The ancients 

 applied topics exclusively to political and forensic 

 oratory ; but some moderns, especially Germans, 

 have employed them for pulpit oratory, and call 

 them, in this case, homeletic topics. They used 

 topics and topology also to signify a theory of the 

 principles which the theologian should follow, in 

 selecting and applying the various passages of the 

 Bible, to prove important doctrines, or to judge of 

 those which are generally used for this purpose. 



TOPOGRAPHY (from ro*, ( , place, and ^afo, 

 I write) ; the accurate description of a country, 

 place, &c. going into details into which geography 

 does not enter. Rivers, rivulets, mountains, hills, 

 forests, rocks, roads, particulaily inhabited places, 

 bridges, &c., are proper subjects for topography. 

 Topographical maps are such as treat of all these 

 subjects, and even show the variety of soils, &c. 

 The angle of declination of elevated plains, moun- 

 tains, &c., forms a particularly important subject of 

 topographical surveys. Lehmann has invented a 

 very excellent mode of preparing topographical maps. 



TOR.A (Hebrew, the law) signifies the five 



