THE 



335 



THE 



and by his talents he became one of the principal supports 

 of the aristocratic party. So long as Alexander the Great 

 lived, his adversaries could not venture anything openly 

 against him ; hut no sooner had the king died than the 

 popular party again expelled Theopompus. He now took 

 refuge in Egypt under the protection of Ptolemaeus, the 

 son of Lagus, during whose reign he remained unmolested. 

 But his successor Ptolemaeus Philadelphus was ill disposed 

 towards him, and if Theopompus had not been advised by 

 some friends to quit the country, he would have been put 

 to death. Whither he now fled, what were his subsequent 

 fortunes, and where he died, are questions to which no 

 answer can be given, though it is highly probable that he 

 died about, or shortly after 308 B.C. 



The loss of the works of Theopompus, of which we now 

 only possess numerous fragments, is one of the greatest 

 that antient history has sustained. The following list con- 

 tains the works he is known to have written : 



1. An abridgement of the work of Herodotus ('ETrirn/i?} 

 rwv 'Hj.or.'TLi' iTropiwi/). This epitome is mentioned by 

 Suidas and several other grammarians. Modern critics 

 think it highly improbable that Theopompus should have 

 undertaken such a task, and that it was probably the work 

 of some grammarian, who published it under the name of 

 the historian. The reasons adduced for this opinion are 

 not satisfactory, and it is not improbable that Theopompus 

 mav have made this abridgement as a first attempt at his- 

 torical composition. A few fragments of it are still 

 extant. 



J. A more important work was a history of Greece 

 "KXXrp'ticai ioropiai, or SuiraSic 'EXXTjvucwi'). It took up the 

 history of Greece where Thucydides breaks off, B.C. 411, 

 and carried the events down to the battle of Cnidus, B.C. 

 394. The work consisted of twelve books, and many frag- 

 ments are still preserved. 



:;. The history of Philip of Macedonia and his time 

 (*i\iT77W, or simply 'i<rropi'ai\ It contained in 58 books 

 ice from the accession of Philip, or 

 more properly from the foundation of Philippi, down to 

 his death. Five books of it were lost as early as the time 

 of Diodoms Siculus fxvi. 3), and they were probably the 

 same which Photius (Cod., 176, p. 390) mentions as being 

 .1 his time, viz. books 6, 7, 9, 20, and 30. This volu- 

 minous work not only embraced the history of Greece in 

 (lie of the word within the period mentionrd. 



but also treated of those earlier parts of Greek history and 

 of the history of such barbarous nations as he had occasion 

 to mention. These things formed numerous and long 

 digressions in the work, and of their extent we may judge 

 from the fact that Philip III. of Macedonia, alter cutting 

 out these digressions, reduced the work from 58 to 16 

 books. fPhotius, Cod., 176.) We still possess many frag- 

 ments of the work, which the antient writers refer to and 

 quote. 



Besides these historical works, Theopompus wrote many 

 orations, and we know that he also composed Panegyrics 

 on Mausolus, Philip, and Alexander. As regards his 

 character ;us an historian, the antients praise him as a lover 

 of truth, but they also state that he was extravagantly 

 severe in his censure, and unbounded in his praise. His 

 ardent and vehement temper did not allow him to pre- 

 serve that calmness which becomes the historian. He is 

 also charged with having been too fond of the marvellous, 

 and with having for this reason dwelled too much upon 

 the mythical stories of Greece wherever he had occasion 

 to mention them. 



The fragments of Theopompus have been collected by 



Wirhers: ' Theopompi Chii Fragmenta, collegit, disposuit, 



iilicavit, fjusdemque de Vita et Scriptis Commenta- 



;n praemisit,' &c., Lugduni Batavorum, 1829, 8vo. 



, i /s _i T Ti/T"ii * i t* i_ 



pare F. Kocn, Prolegomena 



tin, 1803, 4to. ; A. J. E. Pflugk, De Theopompi Chii 

 l'it'li'1 Scriptis, Berlin, 1827, 8vo. ; Asehbach, Dissertatio 



<npO ''hin n/*torirr>, Frankfort, 1823, 4to. 

 TIIKORBO, a musical instrument of the lute kind, which 

 has long fallen into disuse. The latest employment of it 

 that we can trace was in Handel's oratorio of Esther ( 1720), 

 where it is introduced, with the harp, as an accompani- 

 ment to the air 'Watchful Angels.' This instrument has 

 been called the ' </"A'". > ts tvvo hea(ls having been 



erroneously considered as two necks : and it was commonly 



known under the name of Arch-lute on account of its 

 magnitude. The upper and middle strings were attached 

 to the lower head or nut ; the lower, or base strings, to 

 an upper or additional one. According to Maister Mace 

 (1676), the Theorbo was the old English lute veiy much 

 enlarged, and used chiefly, if not only, as an accompani- 

 ment to the voice. [LuiE..] 



THEOREM (Siupvpa) means properly a thing to be 

 looked at or seen ; and is used in mathematics to signify 

 any proposition which states its conclusion or makes any 

 affirmation or negation ; as distinguished from a PROBLEM, 

 which demands or requires a conclusion to be arrived at, 

 without so much as stating whether that conclusion is even 

 possible. Thus, ' Required to draw a tangent to a circle at 

 a given point,' is a problem ; but ' If a straight line be 

 drawn at right angles to a diameter from its extremity, that 

 straight line is a tangent to the circle,' is a theoerm. The 

 problem asks discovery both of method and demonstration ; 

 the theorem asks demonstration only. 



This distinction, as noticed in detail in PROBLEM, was not 

 made by the older Greek geometers ; Theodosius is the 

 first, as far as we know, who uses the word theorem, but 

 none of his propositions are problems: Pappus is the fust. 

 who uses both terms in the distinctive sense. 



THEORIES OF MOLECULARITY. This important 

 branch of science is directed to connect the known mecha- 

 nical, dynamical, and hydrodynamical laws with those 

 which govern the crystallization of solids, the operation of 

 heat in producing liquidity and gaseity, the action of ca- 

 pillary tubes on fluids, and several other phenomena of 

 constituted matter. The laws which regulate the motions 

 of great masses taken as continuous bodies have been ex- 

 plored with success to an astonishing degree by the genius 

 and labours of -such men as Newton, D'Alembert, and La- 

 place. On the contrary, those law's which govern the con- 

 stitution or elementary arrangement of such bodies are to a 

 great extent absolutely unknown. The ordinary senses of 

 sight, touch, &c. are sufficient to take cognizance of the 

 facts from which the former laws are deduced ; but for the 

 latter it is necessary to apply the most delicate instruments 

 supplied by nature, namely, heat, light, and electricity. 

 The minute world is of more difficult research than the 

 great, the plane sections of a crystal than the elliptic 

 orbits of the planets, the infinitely small than the infinitely 

 great. 



It is not therefore wonderful that this branch of science, 

 which should connect on one uniform basis the phenomena 

 of chemistry, of crystallography, and of the mechanical 

 action of masses, should have attracted the attention of the 

 most able philosophers from the sixteenth to the nineteenth 

 century ; from Boyle to Berzelius, from Newton to Navier 

 and Poisson ; and the present unsatisfactory state of our 

 knowledge on this subject must to a great degree be attri- 

 buted to the neglect of the inductive method, to the sub- 

 stitution of hypotheses for the results of observation. 



The first theory on this subject may be thus stated, that 

 the particles of matter possess the attraction of cohesion, 

 but are repulsed by the action of heat or caloric : when the 

 former preponderates, the body is solid ; when both are 

 equal, it is in a fluid state ; and when the latter exceeds the 

 former, the body is a gas, and prevented from total disper- 

 sion only by the action of gravitation. This is purely hy- 

 pothetic, and forms no more ground for mathematical cal- 

 culation in relation to the phenomena alluded to above, 

 than does the definition of a straight line in Euclid's Ele- 

 ments for the properties established in geometry. The 

 second hypothesis, which of late has been more generally 

 received both by chemists and mathematicians, is that the 

 particles of matter are mutually attractive by a law ana- 

 logous to that of gravitation, but are surrounded by atmo- 

 spheres repulsive one of the other, in the same manner as 

 the particles of elastic fluids. From this hypothesis the equa- 

 tions of equilibrium and of progressive and rotatory motions 

 are deducible ; but as the constitution of such atmospheres 

 mav be modified very much at the will of the calculator, so 

 as still to obtain the same mechanical results (in the manner 

 in which the distribution of the fluid of light in crystal- 

 lized bodies has been by those analysts who have developed 

 the undulatory theory), it seems probable that it will be 

 long before the phenomena of crystallization, liquefaction, 

 &c will from this hypothesis be explained, and the absence 

 of all external action in solids, with the exception of gra- 

 vitation. The difference of the calculations of Navier and 



