This compromise having been accepted, the period from 311 to 350 was one of incessant agitation on the part of the plebeians, of incessant opposition on the part of the patricians, of incessant shifting between the consulship and the military tribunate, according as the patricians or the plebeians were the stronger. On the whole, however, the plebeians gained ground. In 321, the active authority of the censors was limited to eighteen months out of the five years for which they were appointed. In 328, the tribes obtained the right of deliberating on questions of peace and war. In 334, the number of the quæstors was increased to four, to be chosen indiscriminately from either order. Lastly, in 350, or B. C. 404, the system of payment for military service became common. During these forty years the patricians had frequently had recourse to the expedient of appointing a _Dictator_, or supreme magistrate, with unlimited authority for six months. Such an appointment almost always proved a temporary check to the political advancement of the plebeians. In cases of difficulty also, arising from external danger, it was usual to appoint some able man dictator; and it was at such a juncture, in the year 359, that, determined to bring the siege of Veii to a close, the Romans appointed Camillus to this high office. The siege of Veii having terminated so successfully, the Romans were prepared to resume their career of conquest without, and their political agitations within, when both the one and the other received a check from an unexpected quarter. Some cause, now unknown, had thrown the Gauls, or Celtic populations inhabiting the western portion of Central Europe, into commotion; and bursting from their native haunts, a mass of these savages crossed the Alps in quest of plunder and settlements, established a permanent abode in the country adjacent to the Po, and pushed their destructive way through almost the whole length of the peninsula. Rome suffered more severely than any other city. For several months (364-5, or B. C. 390-89) it was in the possession of the savages――its rightful inhabitants, routed in the battle, having dispersed themselves for safety through the surrounding country. At length, however, the Gauls were bribed to return to their homes in the north, leaving Rome in ruins. GRADUAL CONQUEST OF THE PENINSULA――ITALY UNDER THE ROMAN RULE.