EUROPEAN NEWS.; Advices of August 25 by the Ocean Telegraph. Arrival of the Steamship City of Paris at this Port. Definite Conclusion of Peace in Europe. Prussia, Italy, Austria and Bavaria Unite in It. All Troops to Return Home Within Three Weeks. Venetia Freely Ceded to Italy by Austria. A Constitutional Government to be Granted to Hungary. Our Naval Officers Still Enjoying Themselves at St. Petersburgh. The Downfall of Maximilian's Government Conceded. OUTBREAK OF CIVIL WAR IN JAPAN. Extraordinary Demand for U. S. 5-20s in Paris. Large Amount of Gold Shipped to New-York. BY OCEAN TELEGRAPH. THE PEACE NEGOTIATIONS. Conclusion of Peaces--The Treatics Officially signed. The Treaties to be Ratified Immediately. ITALY. Vonetia Freely and Unreservedly Ceded to Victor Emmanuel by Austria. SOUTH GERMANY. The Frankfort Assembly Sanction a Loan of Twelve Millions of Florins. The Prussian Troops Evacuating Mainz. SAXONY. Instructions to the Saxon Ministry. SPAIN. Suspension of Export Duties on Goods Shipped to Cuba. HUNGARY.