It has already been shown that a ton of any kind of freight cannot be laid down at Portland from Detroit, by rail, under $8.80, without a loss to the stockholders, nor to Boston under $9.65, except with the same result; nor at New York _via_ the Great Western, New York Central, and Hudson River roads under $6.82, without actual loss to those roads, so that the case would stand thus:--Detroit to Portland, per ton, _via_ G. T. R., $8.80; Detroit to Boston, do. do., $9.85; Detroit to New York, $6.82. Add $4.00 per ton for ocean freights, and we have in each case respectively, $12.80, $13.85, and $10.82 per ton to Liverpool. Now we maintain that a screw steamer of 1800 tons burden, costing, when completed, $150,000, can carry much cheaper than a road like the Grand Trunk, costing $60,000,000, or the New York Central and its connections. A steamer of that capacity would carry 1,500 tons of freight; 600 tons of coal would run her across the Atlantic, and she could coal from Chicago or Detroit to Newfoundland, and from the latter point to Liverpool. By doing this, she could carry 300 tons more freight than if she coaled for the entire voyage from Chicago to Liverpool. All the principal exports and imports of Michigan, Indiana, Western Ohio, Kentucky, &c., would find their way to Detroit, and this point would of necessity become the great centre of the direct trade between Europe and the States above mentioned. Two steamers per week could be run with profit on the route during the season of navigation; each steamer would make two round trips and a half per season of seven months' navigation, allowing two months for each round trip. At this rate sixteen ocean steamers would be required to make up a semi-weekly line, and were the Canadian canals enlarged and ready for use by the middle of next April, there would be at once sufficient trade to sustain them, at much cheaper rates for freight and passage than is now charged by any route or combination of routes in existence, as the following will show conclusively: Each round trip would give the following sums for freight and passage:--1500 tons of freight at $6 per ton, $9,000; 40 cabin passengers at $50 each, $2,000; 50 steerage do. do. $25 each, $1,250. Total for the trip out, $12,250. Inward bound:--600 tons freight at $6, $3,600; 75 cabin passengers at $60, $4,500; 300 steerage do. do., $30, $9,000--$17,100. Add outward receipts, $12,250. Total, $29,350. The total cost of the trip, including insurance, would not exceed $14,000. Total net profits, $15,250.