THE 



of Dan. Heinfius, Gri-ek and Latiu, fol. Lugd. Bat. 

 1613. Of his hidory of plants, the moft complete is that 

 of Budxus, Greek and Latin, fol. Amft. 16+4. Among 

 tlie moll elleemcd editions of his " Charaaers," which are 

 numerous, we may reckon thofe of If. Cafaubon, of Need- 

 ham, with the notes of Duport, Cantab. 17 12, and of 

 I. Fr. Fifcher, Coburg. 1763. Diog, Laert. Brucker 

 by Enfield. Haller Bib. Bot. 



THEOPHYLACT, named Simocattn, a Greek hiftorian, 

 a native of Greece, but of Egyptian origin, flouriihed about 

 A.D. 612. His liiltory of the reign of the emperor Mau- 

 rice is comprehended in eight books, and terminates with the 

 maflacre of this prince and his children by Phocas. Cafau- 

 bon reckons Simocatta one of the bell of tlie later Greek 

 hillorians. The work juft mentioned was printed at the 

 Louvre, in 1647, fol. and forms a part of the Byzantine hif- 

 torians. An edition of his " Epiftles, Moral, Rural, and 

 Amator)'," was given by Aldus. His " Phyfical Pro- 

 blems" were publilhed firll by Vulcanius at Leyden, and 

 afterwards by Andrew Schottus. Hit " Hiftory of the 

 Habitable Worid" is cited by Euftathius, in his Commen- 

 tary on the Periegefis of Dionyfius. Gen. Biog. 



TiiEoriiYLACT, archbiiliop of Acris, the capital of 

 Bulgaria, was a native of Conftantinople, and flouriflicd 

 under the emperors Michael Ducas, Nicephorus Botoniates, 

 and Alexis Comnenus. After his elevation to the arch- 

 biftiopric of Acris, by the perfuafion of the wife of Ducas, 

 he diligently laboured in propagating the Chriftian faith, 

 and compofed feveral works, which give him r.ink among 

 the principal ecclefiaftical writers of his age. The time of 

 his death is not known; but he was living in 1071. His 

 " Commentaries on the Four Gofpcis, the Acts of the 

 Apoftlcs, and the Epiftles of vSt. Paul," which are his 

 chief work, are for the moft part abridged from Chryfof- 

 tom and others. He alfo wrote " Commentaries on the 

 Minor Prophets." Several editions of his Commentaries 

 have been publilhed in Greek and Latin, and alfo in Latin 

 only. " Seventy-five Epiftles" of this author were publilhed 

 by Meurfuis, in Greek, in 161 7, and a Latin tranflation in 

 1622. Some other trafts have been attributed to this author. 

 Dupin fays, that the Commentaries of Thcophylaft are very 

 ufcful for the literal explanation of the Scriptures : and 

 Lardner obferves, that he quotes no forged writings or 

 apocryphal books of the New Teftament, many of which 

 he excludes by his obfervation on John, i. 31 — 34. that 

 Chrill wrought no miracle in his infancy, or before the 

 time of his public miniftry. Dupin. Lardner. 



THEOPNEUSTiE, e^OTvturai, formed of Qior, God, 

 and ■ativu!, I breathe, an epithet given to enthufiaftical 

 diviners. 



THEOPOLIS, in jineient Geography, a town of Gallia 

 Narbonnenfis, belonging to the Aventici, N.E. of Forum 

 Novum. 



THEOPROPRIA, ©!o~po7n«, formed of ©so;, Go</, and 

 ■sjp!57i, / excel, a defignation given to oracles. See 

 Oracle. 



THEOPSIA, ©EOTTiK, formed of ©io.;, God, and oT.-of/rji, 

 I fee, in Mythology, denoted the appearance of gods. Cicero, 

 Plutai-ch, Arnobius, and Chryfoftom, mention appeai'ances 

 of this kind. 



THEORBO, TiiiORBA, or Tiorba, a mufical inftru- 

 ment, made in form of a large lute ; except that it has two 

 necks, or juga, the fecond and longer of which fuftains the 

 four lall rows of chords, which are to give the deepeft 

 founds. See Lute. 



The word is formed from the French ieorbci or theorbe. 



THE 



and that from the Italian t'lorbe, which fignifies the lame, 

 and which fome will have to be the name of the inventor. 



The theorbo is an inftrument which for many years fuc- 

 ceeded to the lute, in the playing of thorough bafles ; it is 

 faid by fome to have been invented in France, by the fieur 

 Hotteman, and thence introduced into Italy, &c. 



The only difference between the theorbo and the lute is, 

 that the former has eight bafs or thick ftrings twice as long 

 as thofe of the lute ; which cxcefs of length renders their 

 found fo exceedingly fott, and keeps it up fo long a time, 

 that it is no wonder many prefer it to the harpfichord itfelf. 

 At leaft it has this advantage over it, that it is ealily removed 

 from place to place, &c. 



All its ftrings are ufually fingle ; though there are fome 

 who double the bafs-ftrings with a little oclave, or the fmall 

 ftrings with an unifon ; in which cafe, bearing more re- 

 femblance to the lute than the common theorbo, the Italians 

 call it the arcileuto, or arch-lute. 



THEOREM, in the Mathematical Method, a propofition 

 which terminates in theory, and which confiders the properties 

 of things already made or done. 



Or, a theorem is a fpeculative propofitipn, deduced from 

 feveral definitions compared together. Thus, if a triangle 

 be compai-ed with a parallelogram ftanding on the fame bafe, 

 and of the fame altitude, and 'partly from their immediate 

 definitions, and partly from other of their properties already 

 determined, it is inferred, that tlie parallelogram is double 

 the triangle : that propofition is the theorem. 

 Theorem ftands contradiftinguiftied from problem. 

 There are two things to be chiefly regarded in every 

 theorem, ijiz. the propofition and the demonftration : in the 

 firft is exprefr^d what agrees to fome certain thing under 

 certain conditions, and what does not. 



In the latter, the reafons are laid down, by which the 

 iinderftanding comes to conceive, that it does or does not 

 agree to them. 



Theorems are of various kinds : as, 



Theorem, Umverfal, is that which extends to any quan- 

 tity without reftriftion, univerfally. As this, that the 

 reftangle of the fum and difl"erence of any two quantities 

 is equal to the difference of their fquares. 



Theorem, Particular, is that which extends only to a 

 particular quantity. As this: in an equilateral right-lined 

 triangle, each of the angles is fixty degrees. 



Theorem, Negative, is that which expreffes the impofli- 

 bility of any aflertion. As, that the fum of two biqua- 

 drate numbers cannot make a fquare number. 



Theokem, Local, is that which relates to a furface. As, 

 that triangles of the fame bafe and altitude are equal. 



Theorem, Plane, is that which either relates to a reftili- 

 near furface, or to one terminated by the circumference of a 

 circle. As, that all angles in the fame fegment of a circle 

 are equal. 



Theorem, Solid, is that which confiders a fpace ter- 

 minated by a folid ; that is, by any of the three conic 

 feflions. E. gr. this : that if a right line cut two afymp- 

 totic parabolas,' its two parts terminated by them fliall be 

 equal. See Solid. 



Theorem, Reciprocal, is one whofe converfe is true. 

 As, that if a triangle have two equal fides, it muft have 

 two equal angles : the converfe of which is likewife true, 

 that if it have two equal angles, it muft have two equal 

 fides. 



Theorem, in Algebra and Anahfts, is fometimes tifed 

 to denote a rule, particularly when that rule is expreffed 

 in fymbols or formula, of which there is of courfe a great 

 number j but of thefe, fome few, either from their im- 

 portance. 



