SEMITONE, an interval in music, whose ratio is 16 : 15, as c c Z. SENATUS, according to the etymological meaning of the word, is "an assembly of elders," and this is the sense which the Roman writers attach to the earliest senate of Rouse. The number of senators in the Greek republics, as well as at Rome, always bore a certain relation to the number of tribes of which the state was composed. Hence, as long as Attica was divided into four tribes, the number of senators was 400; and when Cleisthenee divided the country into ten tribes, he increased the number of senators to 500. As long as Rome only comprehended one tribe, the Latins of the city on the Palatine, their senate consisted of only 100 members. After the accession of a second tribe, the number of senators was raised to 200 ; and when a third tribe was united with them, the number of senators was increased to 300. Each of the three Roman tribes was divided into ten curiae, and each curia into ten gentes, and the same number of decuries, containing, according to Gottling, parts of several gentes, and made for purposes of representation. At the head of each gene there was a decurio, who, according to Niebuhr, by virtue of this office was a senator, or a representative of his Bens in the senate. But Walter (' Gesch. des Rom. Rechts,') justly observes that the age of a decurio, who was at the same time a military officer, and consequently must always have been a young man and able to bear arms, does not appear to be consistent with the age and duties of a senator. It is much more probable that each decury elected from its own body one by whom it was represented in the senate. Each curia was thus represented by ten senators, who were called a "decuria aenatorum" (Liv., i. 7). At the head of this decuria senatorum was a curio, and the ten heads of the decuries, when the senate consisted of only 100 members, or ten decuries, were the "decent primi," from among whom the king chose one as princeps senatus. It appears that when the Ramnes and Titles became united, and the senate consisted of twenty decuries, the ten decuries of the Ramnes with their decent priori still retained for a time a kind of superiority over the 'Pities. (Dionys. Hal., ii.; Plut., 'Num.,' 3.) The senators representing the Ramnes gave their votea first, and the princeps aenatus was chosen from among them alone_ But the first two tribes must soon have been placed on a footing of equality, no that some of the decent primi, as well as the priacepa senatus, might belong to either of the tribes. (Dionys., 1. c.) After the union of the third tribe, the senators representing the facet two are supposed by Niebuhr to be the "patres tuajorum gentium," and those representing the third to be the " patres minorum gentium," Malin Geseh. d. Rhin. Staatsv. ) on the other hand considers the " patres minorum gentium" to have been the noble plebeiaus whom Tarquinius Priscus admitted into the three old tribes, and who, in con sequence of this, became eligible to the senate. (Cie, ' De Rep.,' 20.) The patres minorum gentium had at first, as Niebuhr (ii., p. 114) supposes, no right to speak in the senate, but merely voted by going over to either party ; and he therefore conceives that they were the " senatorea pedarii." (Gelling, iii. 18 ; Dionys., vii., p. 453.) This name of senatores pedarii might in subsequent times, when all the senators had equal rights, be applied to all senators indiscriminately, as it was their general custom to vote by discessio, or a division. All writers agree that Tarquinius Priscus raised the number of senators to 300, but theemanner iu which this was effected is stated differently-.
Cicero (1. c.) says that the king doubled the existing number et aerators (which would accordingly have been 150), while others (Lite, i. 35 ; Dionys., p. 199) state that he merely added 100 senators, to the existing number of 200. Niebuhr ingeniously reconciles these two statements by the suppositiou that before the time of Tarquinius Priscus some of the gcntes of the first two tribes had become extinct, though it does not follow that the number of the extinct gentes amounted exactly to fifty. But if, as we have supposed, senators were not elected by each gene, but by a decuria, Niehuhr's, supposition must fall to the ground, as it cannot be conceived hoer docuries could become extinct, as they might be formed in such a manner that one large gene would comprehend several decuries, while smaller ones united in forming one decury, and thus were always able to make up a certain number of decuries. The statement of Cicero appears to rest upon a misconception. (Gottling, p. 22S.) Serviva Tullius did not introduce any change in the composition of the senate, but in the reign of the last king, Tarquinius Superbus, the number of senators is said to have become greatly diminished, as many of them were put to death, and others were sent into exile. These vacancies however were filled up immediately after the establishment of the republic by electing into the senate the principal plebeians of the equestrian order. Livy (ii. I) ascribes this completion to L. Junius Brutus; Dionysius (v., p. 287), Plutarch (' Popl.; 11), and Festus (a. v. " qui patres"), to Valerius I'ublicoLs. The number of these new ple beian senators is said to have been 164, but this is utterly incompatible with the subsequent history of Rome. The new plebeian senators. were called Conacripti, in contradistinction to the patrician senators, or patres ; hence the mode of addressing the whole senate " patres i conscripti," that is, " patres et conscripti." The word patres, although in later times used to designate senators in general, was originally another name for patricians. (Liv., ii. 1 ; Fest., a. v. " adlecti Niebuhr, i., p. 327, &c.) The number of 300 senators henceforth remained unaltered fur several centuries. C. Gracchus was the first who attempted an alteration. Livy (' Epit.,' lib. 60) says that he I wished to increase the senate by adding 600 equitea, hut this seems a mistake, and the reading is probably corrupt. Plutarch (' C. Creech.; 5, &c.) says that he added 300 equitea to the 300 senators, and trans ferred to this body the Judicia (publica). All the other writers who mention these events (see the pessages in Gottling, p. 237, noto 3) du not allude to an increase in the number of senators, but merely state that he transferred the Judicia to the equites. A similar attempt was made by the tribune Livius Druaus. (Appian, Civil.,' i. 35.) Sae added 300 equites to the senate, and thus increased its number to 600. [ Sucmc, in Moe. Div.) Four hundred senators were after this time present in a case when many were absent. (Cie. ad Att.', i. 14.) Julius Cesar increased the number of senators to 900, and elected men of the lowest rank into the senate. (Dion Cas., )ill. 47.) This mode of filling up vacancies or increasing the number of senators with freedmen and common soldiers was con tinued after the death of Cesar, and at one time there were more than 1000 senators. (Suet., 'Aug.,' 35.) Augustus again reduced the number to 600. (Dion Cass., lie. 14.) Respecting the number of senators during the empire, we posiesr no direct information. During the latter period of the empire the number of senators appears to have become greatly diminished.