The State Convention will meet in the hall of the House of Delegates at 12 o'clock to-day, the Convention bill having provided that the body shall first assemble at the Capitol. Subsequent sessions will be held in the Mechanics' Institute, where a choice of seats was made yesterday by a large number of delegates.--The general arrangement of the hall, of which we have before given a description, is excellent, and no other place which could have been obtained combines so many advantages for the purpose required. The decorations are appropriate, and not profuse. A large painting of Washington crossing the Delaware, a portrait of Chief Justice Marshall, and busts of Calhoun and Clay, with a tasteful display of drapery over the President's platform, constitute the adornments of the hall. The ladies' gallery, we apprehend, will be more attractive than any other point.