it became the custom to confer this title, as well as that of sevir, upon the probable successor to the throne, when he first entered into public life, and was presented with an equus publicus. The practice of filling all the higher offices in the state from these equites appears to have continued as long as Rome was the centre of the government and the residence of the emperor. After the time of Diocletian, the equites became only a city guard, under the command of the praefectus vigilum; but they still retained, in the time of Valentinianus and Valens, A.D. 364, the second rank in the city, and were not subject to corporal punishment. Respecting the _Magister Equitum_, see DICTATOR. ĔQUŬLĔUS or ĔCŬLĔUS, an instrument of torture, which is supposed to have been so called because it was in the form of a horse. ĔRĂNI (ἔρανοι), were clubs or societies, established for charitable, convivial, commercial, or political purposes. Unions of this kind were called by the general name of ἑταιρίαι, and were often converted to mischievous ends, such as bribery, overawing the public assembly, or influencing courts of justice. In the days of the Roman empire friendly societies, under the name of _erani_, were frequent among the Greek cities, but were looked on with suspicion by the emperors, as leading to political combinations. The _gilds_, or fraternities for mutual aid, among the ancient Saxons, resembled the _erani_ of the Greeks. ERGASTŬLUM, a private prison attached to most Roman farms, where the slaves were made to work in chains. The slaves confined in an ergastulum were also employed to cultivate the fields in chains. Slaves who had displeased their masters were punished by imprisonment in the ergastulum; and in the same place all slaves, who could not be depended upon or were barbarous in their habits, were regularly kept. ĒRĪCĬUS, a military engine full of sharp spikes, which was placed by the gate of the camp to prevent the approach of the enemy. ĔRŌTĬA or ĔRŌTĬDĬA (ἐρώτια or ἐρωτίδια), the most solemn of all the festivals celebrated in the Boeotian town of Thespiae. It took place every fifth year, and in honour of Eros, the principal divinity of the Thespians. Respecting the particulars nothing is known, except that it was solemnised with contests in music and gymnastics. ESSĔDĀRĬI. [ESSEDUM.]