Meanwhile, Urquiza's term had expired. Dr. Derqui, his successor, was suspected of designs against the autonomy of the provincial governments. The assassination of the Governor of San Juan and the succession of a member of an opposite faction, was made the occasion for Federal intervention in the affairs of that province. The government of Buenos Aires protested and it became evident that this untoward event was soon to disturb the peace of the newly formed confederation. The Federal Congress, under Derqui influence, refused to admit the members from Buenos Aires. Mitre marched out at the head of her forces and at the battle of Pavon, September 17, 1861, he overthrew the provincial forces. Buenos Aires remained mistress of the situation. The governments of certain provinces had been imposed on their people by the Derqui administration, or they were obnoxious to the triumphant Buenos Aires party. They were overthrown and Derqui was deposed. Happily for the Argentine, Mitre was a sincere patriot and, though young, was moderate and conciliatory. Made president of the republic as the representative of the victorious Buenos Aireans, he set about the final reorganisation of constitutional government in a spirit of unselfishness and with a foresight and skill that greatly aided to save his country from the sterilising anarchy of civil war. The accession of Mitre in 1862 marked the end of the period of uncertainty. The government of the Argentine Republic was now finally and definitely established and fixed, after fifty-two years of conflict. The constitution of 1853 was left unamended, except that Buenos Aires became the seat of federal government without being separated from its province or ceasing to be the provincial capital. The free international navigation of the rivers was not interfered with, and Buenos Aires abandoned her pretensions to special commercial privileges. She was thenceforward more and more the centre of gravitation and power for the whole republic, but her influence came from legitimate natural causes and was exercised within constitutional limits. The autonomy of the provinces was not interfered with, and it was no longer possible, even in the remotest districts, for a caudillo to rally at his call the gauchos, always ready for a raid, a campaign, or an invasion. [Illustration: BARTOLOME MITRE. [From a steel engraving.]]