The three staunch and magnificent steamers belonging to the company, the Plymouth Rock, Western World and Mississippi, owing to the hard times have been laid up at their dock since the fall of 1857, to the great regret of the public generally, as well as to the detriment of the business interest of our city. With the return of a more prosperous era they will doubtless be again placed in commission. The line formed by these boats is the most pleasant and expeditious medium of communication between the East and the West and Southwest, and cannot fail to be well patronized, especially now that the Dayton and Michigan Railroad is completed, which will bring a large amount of both freight and passenger traffic by way of Detroit that formerly sought other routes. The rolling stock now on the road consists of ninety-eight engines, seventy first class passenger cars, twelve second class cars; twenty-nine baggage cars, and two thousand seven hundred and seventy-eight freight cars, making a total of two thousand eight hundred and eighty-nine cars and all of which were built in the company's own shops. This road is one hundred and eighty-eight miles long, and has been in operation throughout its whole extent since November, 1858. It is deserving of the distinctive appellation of the _Back Bone Road of Michigan_, having been of incalculable value in developing the resources of the region through which it is located, decidedly one of the richest and most important in the West. The principal towns and cities upon its line are Pontiac, Fentonville, St. Johns, Ionia, Grand Rapids and Grand Haven. The growth of these places has received a great impetus since its completion, while numerous villages have also sprung into being as if by magic at various points along the line. These changes are plainly visible in the improved trade of our city, and the increase from the same cause, must continue to be strongly marked. Last season over one-fourth of the wheat and wool received here was by this new route, and a number of vessels loaded at the company's noble and spacious wharf for European ports direct. Within the year past, the company have completed one of the finest railway wharves in the world. It is 1,500 feet long by 90 broad, the west end of which is occupied by the freight house, the dimensions of which are 450 by 132 feet. One of the most important events to Detroit and the entire West, that has transpired for many years, is the completion of this great thoroughfare. The link from Port Huron to this city was opened to traffic on the 21st of November, since which date the businesses crowding upon it has fully equaled its capacity. It is the Minerva of railways, having reached at a single bound a condition of prosperity outrivaling many of the oldest established roads on the continent.