Wm. Lyon McKenzie, now a member ot the Canadian Legislature, has written a letter to the " New York Tribune," proposing a new route to Europe. The plan is to have lines of railroad ending in some harbor on the Atlantic, north of the Straits of Belisle,arid from thence steamships to Galway, in Ireland, the nearest European port. He ingeniously proposes to house in the line in those parts of our continent subject to heavy snow storms through which it may pass. He calculates that by this route communications could be received and transmitted to Europe in three days less than by any of the present established routes. We have no noubt of his correctness so far as time is concerned, and the proposition to house in a line of railroad with strong framing and coarse boards, is worthy ol consideration for more objects than protection from snow. But time is not the only economy to be considered in proposing any new route or plan for mercantile purposes, although it is a most important one. If it were so, neither the Collins' nor Cunard steamers could compete with a line established to run between Boston and Liverpool, for nearly a day's voyage can be saved by this route in comparison with that between New York and Liverpool. The rails are already laid to save one days' time in a voyage to Europe, and yet no particular advantage is taken of them. It would indeed be a good thing if a railroad line connected the nearest points of our continent, or one of its contiguous islands, with the nearest one in Europe, and also with the nearest point of Asia, but such a line, unless it could compete in economy with a longer route, would never be supported.