The completion of this stupendous bond of connection between the Eastern and Western States, Canada and Europe, will render markets available which were before difficult of access, and enable far-distant countries to exchange their products at all seasons. The Grand Trunk may be called the first section of the PACIFIC RAILROAD, as it already communicates with the Mississippi through Michigan, Illinois and Wisconsin Railroads, and we expect to see the line completed from the Mississippi to California. It is not easy to form an estimate of the amount of traffic and intercourse that the 1,150 miles of Grand Trunk Railway will bring to Michigan and the neighboring States. A junction has been already formed with that model of western lines the Michigan Central by which freight and passengers reach Chicago and the numerous lines which diverge from that great commercial city. It is probable that another junction will be made with the Detroit and Milwaukee Railway by means of a branch from Port Huron to Owasso. In this case there will be a direct line across Michigan connecting with the Milwaukee railroads by the ferry across the lake, and penetrating into Iowa, Minnesota, Nebraska, and Oregon by lines which have not yet been traced on the railway maps of the United States. The ostensible western terminus of this road is at Windsor, opposite our city, but it is practically as much a Detroit road as any that can be named. The connections with the other routes centering here is made by a number of ferry boats of the most staunch and powerful description. The receipts by this route of general merchandise consigned to the cities and points westward of us is immense, and it enjoys a large and growing local traffic. The main line of the Southern Michigan and Northern Indiana Railroad, which taps a rich and important portion of Michigan, is 461 miles in length. The business on this line has recently shown a decided improvement. The D. and T. Road, which is 65 miles in length, was opened to traffic in January 1857. It was built by the "Detroit, Monroe, and Toledo Railroad Company," who leased it to the Michigan Southern Road. It is now an important link in the great railway system extending from the East to the Great Southwest, of which system, Detroit, from its favorable position, has become the centre and soul. Since the opening of the Grand Trunk, in November, a large amount of freight has passed through, billed for Liverpool direct, a species of freight which must steadily increase. L. P. Knight is agent at Detroit. The office is in the depot building of the Detroit and Milwaukee Railway.