There have been secessionists per se—men who have been plotting a dissolution of the Union, in some of the Southern States, for more than twenty years past. Until quite recently, however, they have remained in a meagre minority in every State except South Carolina, if, indeed, they ever were in a majority even in that State. Until within some two or three years past, the disunion sentiment at the South was limited to a class of ambitious politicians, who conceived that their chances for political preferment would be better in a new Southern Confederacy, than in the present Federal Union. This has been the ruling cause of the disaffection to the Union which has prevailed more or less in some of the Southern States, ever since Mr. Calhoun conceived the idea of attaining, in a Southern Confederacy, to that elevated position which he vainly strove for in the Union made by our fathers. But until recently, men who represented the property and enterprise of the cotton-planting States, and who were seeking to better their condition by other means than political preferment, have been slow to yield their sympathy and support to mere political schemers and agitators, for the advancement of their selfish and ambitious aspirations.

It is manifest, however, that within some two or three years past, the disunionists in the cotton States have been receiving large accessions from a new class of citizens—those who represent the great planting interests of that section. These gentlemen are, as a body, intelligent and enterprising, and act from motives, as much as mere politicians do. What new motive, then, has lately brought so many of them en rapport with the advocates of disunion? Every one knows that the election of a Republican President is not the cause of the great increase of disunion sentiment now so manifest in the cotton States. Every one knows that this has been merely seized upon as a pretext for a secession movement which the hearts of the people had been previously prepared for. If some new and powerful motive had riot been presented to the people of those States, to induce them to view disunion in some new light, the secession movement of 1860 would have received no more countenance from them, than did those of 1832 and 1850.

Now, what is this new motive, which has wrought so great a change in public sentiment? Every careful observer of the “signs of the times,” will recognise the truth of our averment, when we state that the disunion sentiment has been gaining ground in the cotton States, ever since the proposition to reopen the African slave trade began to be agitated, and viewed as a measure possible of attainment; and that it has advanced pari passu with the change of opinion in favor of that measure.

The increasing demand for cotton, and the high price of that great staple for some years past, has stimulated its producers to extend its cultivation to the utmost of their ability. The great check upon their enterprise in this direction has been the high and constantly—increasing prices of negro laborers. Slave labor being the principal ingredient in the cost of cotton producing, to cheapen the cost of that labor has of course been a great desideratum with those engaged in its cultivation. The proposition to reopen the African slave trade presented the only possible mode of effecting this desired result; and it was only necessary to inspire some degree of faith in the practicability of that measure, to arouse the wildest enthusiasm in its favor.

A little reflection, however, satisfied every man of ordinary sense, of the utter hopelessness of attaining this object in the Union. But in a Southern Confederacy, where the reign of “King Cotton” would be supreme, the measure was conceived to be perfectly feasible. The hope of obtaining negro laborers at one-tenth of their present cost, was a powerful argument addressed to men who were directing all their energies to the extension of cotton planting. The visions of wealth which this prospect opened up to their excited imaginations, did more to shake their loyalty to the Union in one single year, than all the appeals of ambitious politicians had previously done in twenty years. Herein, we think, lies the secret of the great progress of disunion sentiments in the cotton-planting States within the last two or three years.

We sincerely believe that this design of reopening the African slave trade is the most powerful motive now operating upon the Southern mind, in favor of a secession movement. This view of the case affords a solution of the fact, that the Secessionists of the cotton States do not desire the border or grain-growing slave States to join them, at first, in their revolutionary movement. They want the cotton States alone to secede, and set up a new Confederacy, which the border slave States may come into after a while. In other words, they want the cotton States alone to have the framing of the Constitution of the new Confederacy. They know that a Constitution made by all of the slaveholding States, would contain a prohibition of the slave trade. Hence, such States as Maryland, Virginia, North Carolina, &c., whose interests are directly opposed to the importation of slaves from Africa, are not to be trusted to aid in making the Constitution of the new Confederacy; but when the cotton States shall have made one to suit themselves, and gotten the slave trade fairly under way, they may come into it if they see fit.

The avowed motives of the secessionists, for the revolutionary movement now on foot, are so manifestly inadequate, as a justification or even an excuse for that movement, that every reflecting mind must be satisfied that their real motives are kept in the background. The most prominent of these real motives is, unquestionably, an avaricious passion for cheap negroes.