On the 31st of August, General Fremont issued a Proclamation from St. Louis, declaring, among other things, that "The property, real and personal, of all persons in the State of Missouri who shall take up arms against the United States, or who shall be directly proven to have taken an active part with their enemies in the field, shall be confiscated t the public use, and their slaves, if any they have, are hereby declared free men." We have now a Proclamation from Provost-Marshall McKinstry, dated the 13th, giving practical effect to that of General Fremont, in the case of Thomas L. Snead, of St. Louis, convicted of having"taken an active part with the enemies of his country," whose two slaves, Frank Lewis and Hiram Reed, are, consequently, "declared to be free, and for ever discharged from the bond of servitude." This is the first proceeding under the act of the late Congress, entitled, "An Act to confiscate property used for insurrectionary purposes," of which section 4 is as follows:

"Sec. 4. And be it further enacted, That whenever any person claiming to be entitled to the service or labor of any other person, under the laws of any state, shall employ such person in aiding or promoting any insurrection, or in resisting the laws of the United States, or shall permit him to be so employed, he shall forfeit all right to such service or labor, and the person whose labor or service is thus claimed shall be thenceforth discharged therefrom , any law to the contrary notwithstanding.

A literal construction of this law would only authorize the emancipation of such slaves as have been individually employed by their masters in the3 rebel service, to prove which would provably in most cases be impossible, or at least involve long and complicated investigation. General Fremont, rightly interpreting the sentiment of the nation, and adverse to half measures, has given the law the only application which can be at all practical and useful in the present emergency. For it is idle, discouraging to all earnest men, and damaging to our cause throughout the world, to discriminate , or to appear to discriminate, between the different kinds of rebel property and unfavorably to the slave. We stultify ourselves, and justly incur the charge of weakness and vacillation, and, what is worse, treachery to the holy cause of human freedom, when we boldly confiscate the ships, and houses, and cattle of the rebel in arms, and yet refuse freedom to his slave, whom he claims as property, except such slave has actually been employed against the nation.

It has been intimated that the government would disapprove of General Fremont's proclamation. We discredit the report. Considerations of policy, or false notions of conciliation, may have hitherto induced the Administration to treat certain "delicate questions" --for it is in this dainty way that a portion of the press speak of the atrocity of Slavery--with great circumspection, and to affect a desire to keep them entirely out of the contest, just as if the whole world does not know that Slavery is at the beginning and the end, is the very essence and body, the motive and sustaining power of the present struggle on the part of the rebel States. But we hope the stern teachings of the past five months have taught it the folly of masking a purpose which must sooner or later be avowed, and through the execution of which alone can the country be restored and its peace and prosperity secured.

We have sung paeans to the Union right loudly, and flaunted our Star Spangled Banner right grandly, and proclaimed to mankind that it was only to uphold the one and perpetuate the other, that we have rushed to the red fields of war, and poured out freely our treasure and our blood. But we have failed to arouse the enthusiasm of men abroad, and have not always secured their sympathy.