The Oriental Republic of the Uruguay, like the greater part of the Republics of South America, was a prey to intestine disputes; and the occasion then was the pretension of two Generals to the Presidency, viz: Rivera and Ouribes. Rivera, being more successful, succeeded after several victories, in driving away Ouribes, and gained possession of the power which he had held. The latter, being expelled, took refuge in Buenos Ayres, where the Dictator, Rosas, received him, together with many Oriental emigrants, and employed them against his enemy, who were then under the command of General Lavalle. Lavalle being conquered, the ferocious Ex-president of Montevideo undertook to regain his lost power in his own country. In that Rosas found the object most agreeable to his wishes; that is, the destruction of the Unitarians, or Centralists, his mortal enemies, who were supported by the Oriental State; and the ruin of a neighboring Republic, his rival, which disputed with him the supremacy of the immense river, by throwing into her bosom the most terrible elements of civil war. At the time when I embarked on the river, the Oriental army was at San Jose de Uruguay, and that of Ouribes at La Bajada, the capital of the province of Entre Rios, both making preparations for a great conflict. The army of Corrientes then made arrangements for uniting with the Oriental. I was to go up the Parana to Corrientes, pass over a distance of more than six hundred miles, between two banks occupied by the enemy, where I would be unable to anchor, unless at islands and desert places. ------------------------------------------------------------------------ CHAPTER XVI. ORIGIN OF THE WAR BETWEEN MONTEVIDEO AND BUENOS AYRES.—CHARACTER AND CONDUCT OF ROSAS, OURIBES—THE CENTRALISTS, CALLED UNITARIANS, OPPOSED TO THE REPUBLICANS. As has been said, the war in Montevideo was caused by the personal ambition of the two generals, Ouribes and Rivera, who were aspirants for the Presidency of the republic. The former was defeated by the latter, about the year 1840, and obliged to emigrate to Buenos Ayres. At that time Rosas, the tyrant of Buenos Ayres, was engaged in war with the Centralists, or Unitarians, who were the national and liberal party, and were led by Generals Lavalle and Paz. Rosas received Ouribes and many of his partizans, and gave them immediate employment in his own army, while he conferred the supreme command of it upon the emigrant General. Ouribes, being able to bring many reinforcements to the tyrant's army, which was already strong, defeated Lavalle, who died in the upper provinces of the Argentine Republic (I think Mendoza,) in a surprise. General Paz, by intrigues and dissensions, was obliged to abandon the struggle, after the brilliant victory of Caguazú, and to return to Montevideo, where the greater part of the Centralists who had fought against Rosas had retreated.