Let the Nashville and Chattanooga Railroad receive due credit for the part it has played in promoting the success of the campaign and 'saving the Army of the Cumberland.' Railroads and all other channels of commerce contribute most efficiently to the success of the great effort of our Government to restore the integrity of the Union: let them receive due credit, and be rightly remembered when the great conflict is ended. These facts may serve to suggest the value of the various commercial facilities as means of political unitization. A country without the means of travel and transportation may readily separate into independent fragments whenever any arbitrary institution, as that of slavery, develops antagonism between different geographical sections; and in that case the arbitrary institution would triumph, and civilization would be thrown backward. But in a country which speaks the same language, and is checkered all over by the pathways of commercial and social intercourse--since there is no place for division except by the rupture of innumerable ligaments--the integrity of its oneness will maintain itself; and if necessary to this end, the arbitrary institution, or cause of attempted rupture, whatever It may be, will be swept out of existence. The vindication of national unity is the great issue; the abasement of slavery a subordinate one. Here, then, may we perceive some reasons why our labor and sacrifice for the restoration of the Union are not given in vain; that we are not struggling to sustain a structure which will be liable at any time to pass into the history of the 'fall of empires.' We have the encouragement of new conditions--of conditions which give a warrant, wherever they obtain, for the permanence of political unity. Subdue the present rebellion, reinstate the Union, multiply the facilities for social intercourse and the mutual exchange of products, especially railroads, wherever there is sufficient promise of a need; and our country, thus knit together and united, has nothing to fear from the madness of local factions. Permeate the body politic in all its members by the nerves, veins, and arteries of a vital circulation, and it becomes an organized unity which is not susceptible of division into upper or lower, right or left, except by the destruction of the entire organism. But admitting that continental unity is to obtain some day, still the question as to whether now is or is not the time for it to assume a more distinct form, brings us by a rational necessity to a brief notice of the influence of European diplomacy and the contingency of foreign intervention.