The mail steamer Britannia, which left Boston on the 1st
instant, arrived at Liverpool late yesterday evening. There are advice* from Vera (Non'
to the 18th July; but they consist chiefly of reports that seem to demand further authentication. No great event had occurred at the seat of war. Colonel Pearce, on his way to General Scott at Puebla, with a detachment of 2,500 men' had been attacked at the National Bridge, by guerillas, and compelled to fall back; but the Mexicans lost 150 men. Generals Cad- wallader and Pillow are reported to have "defeated the Mexicans at La- begs.." The Mexican Government is said to have appointed three Corn- misioners, named Garastiso, Baranda, and Tomei, to treat with Mr. Trist, the American Plenipotentiary, for a peace; and Santa Anna is understood to be in favour of that object.
In the United States, the reports of the wheat harvest are, that it was over in the South and West, begun in the North, abundant, and good; maize, enormous in quantity. At New York flour had risen about 2s. per barrel, and stood at 36s. and 37s. The rate of exchange on London was s# to 65- premium.
From Canada we learn that the session of the local Parliament was closed on the 28th of July, after the Legislature had repealed all the differential duties."