SEDITIOUS MEETINGS ACT.—The town of Petersfield was thrown into great confusion on Sunday last, by the appearance of a number of persons marching in military array; armed with muskets and sticks; and who, after parading the town, and exciting universal dismay, attacked a house occupied by a cooper, of which they took forcible possession. We understand, the authors of this outrage, which is said to have been committed under the direction of a celebrated Radical Reformer, in Hampshire, are known; and that an information, under the Seditious Meetings Act, has been laid against them. This will be the first instance of prosecution under this Act.