"Three great canals, (one of them longer than the Erie Canal,) embracing in their aggregate length about one thousand miles, are to connect the Ohio with Lake Erie; while another deep and capacious channel, excavated for nearly thirty miles through solid rock, unites Lake Michigan with the navigable waters of the Illinois. In addition to these broad avenues of trade, they are constructing lines of railroads not less than fifteen hundred miles in extent, in order to reach with more case and speed the lakes through which they seek a conveyance to the seaboard. The circumstance, moreover, is particularly important, that the public works of each of these great communities are arranged on a harmonious plan, each having a main line, supported and enriched by lateral and tributary branches, thereby bringing the industry of their people into prompt and profitable action; while the systems themselves are again united, on a grander scale, with Lake Erie as its common centre." The various streams of the trade from the interior being thus collected in the lakes--which form, as it were, the heart of the system--there are two great channels for its redistribution and dispersion through the markets of the world. These are the St Lawrence, and the Erie Canal with the Hudson; and the vital question as regards the prosperity of Canada is, by which of these outlets will the concentrated traffic of the lakes find its way to the ocean? Mr Johnston has devoted considerable attention to this subject, and assigns two good reasons for believing that the St Lawrence is destined immensely to increase the share which it has already secured. In the first place, the American artery is already surcharged and choked up;--notwithstanding all the efforts that have been made to expedite the traffic on the Erie Canal, it has been found wholly inadequate to accommodate the immense trade pouring in from the west; and, secondly, the route of the St Lawrence, besides being the more expeditious, is now found to be the cheaper one. In a document issued by the Executive Council of Upper Canada, it is mentioned that the Great Ohio Railway Company, having occasion to import about 11,000 tons of railway iron from England, made special inquiries as to the relative cost of transport by the St Lawrence and New York routes, the result of which was the preference of the former, the saving on the inland transport alone being 11,000 dollars. There seems good reason to expect that a considerable portion of the Mississippi trade may be diverted into the Canadian channel; but putting this out of view altogether, it is certain that the navigation of this glorious river is every year becoming of greater importance to the United States, as well as to Britain: let us hope that it is destined ever to bear on its broad breast the blessings of peace and mutual prosperity to both nations.