The St. Lawrence River is the natural outlet of the Lakes, and, if rendered accessible to us by canals, must be the cheapest outlet. It is well known that a few years ago corn was worth on the prairies of Illinois only ten cents per bushel, when the same article was selling in New York at seventy cents, six sevenths of the price being consumed in transportation. The consequence was, that many farmers found it more for their interest to use their surplus corn for fuel than to sell it for ten cents. The great disturbance in values caused by the war, and the vast demand for grain and forage for the army, have reduced this disproportion in prices very much for the time, but it may be looked for again on the return of peace. Now it would seem that one of the most important questions to be settled in this country is how to cheapen food. If, by the construction of these canals to give access to the St. Lawrence, grain can be laid down in New York ten cents a bushel cheaper than it now is done, the saving on the present shipments of breadstuffs from the Lakes would be ten millions of dollars annually. It is probable, however, that the saving in freight would be much greater than this, if the canals were built of sufficient capacity to admit the largest class of Lake vessels. This direct trade between the Upper Lakes and Europe was commenced a few years before the breaking out of the Rebellion, and was beginning to assume important proportions, when the war put a stop to it, as it has to so much of our foreign commerce. While the present article was in preparation, the bill for the construction of these canals passed the House of Representatives, as also one for the deepening of the Illinois and Michigan Canal, concerning which the report of the Hon. Isaac N. Arnold of Illinois, chairman of the committee of the House on the defence of lakes and rivers, thus remarks:--"The realization of the grand idea of a ship-canal from Lake Michigan to the Mississippi, for military and commercial purposes, is the great work of the age. In effect, commercially, it turns the Mississippi into Lake Michigan, and makes an outlet for the Great Lakes at New Orleans, and of the Mississippi at New York. It brings together the two great systems of water communication of our country,--the Great Lakes and the St. Lawrence, and the canals connecting the Lakes with the ocean on the east, and the Mississippi and Missouri, with all their tributaries, on the west and south. This communication, so vast, can be effected at small expense, and with no long delay. It is but carrying out the plan of Nature. A great river, rivalling the St. Lawrence in volume, at no distant day was discharged from Lake Michigan, by the Illinois, into the Mississippi. Its banks, its currents, its islands, and deposits can still be easily traced, and it only needs a deepening of the present channel for a few miles, to reopen a magnificent river from Lake Michigan to the Mississippi."