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.

The Dayton and Michigan Railroad was completed last fall, placing us within a few hours' ride of the Queen City of the West. This is justly regarded as a most important route to our city, and will develop new features to some of our leading business interests. The consumer of our State will have the benefit of lower prices for the products of Kentucky, Tennessee, Louisiana, and the West Indies. The want of direct communication between Detroit and New Orleans has long been felt. Sugars and molasses can now be laid down here for fifty cents per 100 lbs., including all charges from New Orleans, via the Mississippi and Ohio Rivers, and D. and M. Railway, giving us, in a word, the benefits of as low freights in winter as in summer. With the cost of transportation thus reduced to a merely nominal standard, prices of Southern products will be upon an average no higher here than in Louisville. It is more than probable, nay, quite certain, that the advantages which must ultimately accrue to the State from our connection with Cincinnati per se, if not so general, will be even more marked and important than those to which we have above referred. The prices of provisions will be equalized, giving our lumbermen and miners the benefit of reduced rates throughout most of the year, and when speculation is rampant, and the price of pork, the great staple of our neighbors, reaches an extreme figure—as has been the case for two successive seasons, and will be the case again—our farmers will reap the benefit of the movement. The growth of Cincinnati is altogether without parallel in the world, taking into account the character of that growth—its quality, so to speak. All its great interests, particularly its manufactures, have kept pace with its numerical increase. It is indeed difficult to determine whether manufactures or commerce is most intimately identified with its prosperity. The connection with her will give us new and desirable customers for some of our surplus products, particularly our choice lumber.

The entire line of the Flint and Pere Marquette Railroad, as located, is 172-½ miles; track laid and completed, 7-¾ miles; additional length graded 24-½ miles, the ties for which have all been delivered.

It is thought that hereafter twenty miles per year will be completed without difficulty until the whole is completed. This road will be important in developing the resources of a very rich tract of country.

On the line of Amboy, Lansing, and Grand Traverse Railroad, the entire distance from Owasso to Lansing, twenty-six miles, is ready for the iron, except three miles. On the division from Lansing to Albion, thirty-six miles, the work of grading and furnishing ties is progressing, and some one hundred men at work. Between Owasso and Saginaw, thirty-three miles, arrangements are nearly completed to start the work. The work of grading and preparing for the iron is done by local subscriptions, of which $3,000 per mile has been subscribed and is being paid.

The existence of copper on the shores of Lake Superior appears to have been known to the earliest travelers, but it has been only a few years since it has entered largely into Western commerce. But the country had long been a favorite resort for fur traders, and as long ago as 1809, and perhaps still further back, the Northwest Company (British) owned vessels on Lake Superior. This organization was at that period the great trading company of the region in question, the operations of the Hudson's Bay Company being confined chiefly to the region further north. At the period of which we speak, the bulk of the trading was done by means of birch canoes, some of them large enough to carry two or three tons. With these, the traders passed up to the Indian settlements in the fall, with goods, provisions, and trinkets, usually returning to the trading posts during the month of June with the furs which they had procured in exchange. Mackinac and the Saut were trading posts at an early day. At a somewhat later period, the Northwest Company had an agency on an island in Lake Huron, not far from the month of Saut river. The formation of the American Fur Company was of more recent date, that company dating its origin during the war of 1812, or soon after.

Prior to the building of the canal, a number of steamers had been taken over the portage to Lake Superior, but so far as our knowledge extends, only one or two craft larger than a canoe were ever taken over the rapids, one of which was the schooner Mink. She was built of red cedar, on Lake Superior, about the year 1816, and was of some forty tons burden. She became the property of Mack & Conant, who had her brought down the rapids. In making the descent she suffered some injury by striking against a rock, but, notwithstanding this mishap, she lived long enough to ride out many a stormy sea, running for several years in the trade between Buffalo and the City of the Straits. Shubael Conant, Esq., at this day an honored citizen of Detroit, was one of the firm that purchased the Mink.

In the spring of 1845, the fleet on Lake Superior consisted of the schooner White Fish, belonging to the Hudson's Bay Company, the Siscowit, belonging to the American Fur Company, and the Algonquin, owned by a Mr. Mendenhall. The same year the schooners Napoleon, Swallow, Uncle Tom, Merchant, Chippewa, Ocean, and Fur Trader, were all added. In 1845, the propeller Independence, the first steamer that ever floated on Lake Superior, was taken across the portage, and the next year the Julia Palmer followed her, she being the first side-wheel steamer. In the winter of 1848-9, the schooner Napoleon was converted into a propeller. In 1850, the propeller Manhattan was hauled over by the Messrs. Turner, and the Monticello in 1851, by Col. McKnight. The latter was lost the same fall, and Col. McK. supplied her place the next winter with the Baltimore. In 1853 or 1854, E. B. Ward took over the Sam Ward, and Col. McKnight took the propeller Peninsula over in the winter of 1852 or 1853.