'We have reserved to the last the consideration of that possible outcoming of the war which is looked upon with most dread, both at the South and the North; from which both sections almost equally shrink as the possible issue; but which, nevertheless, may be forced on them by the logic of events, and that, too, at an earlier day than has been indicated by the expectations of either. While we write, the startling announcement is made from St. Louis that Major-General Fremont has been forced, by the threatening progress of the Southern armies, to declare martial law for the whole State of Missouri, coupled with the offer of freedom to the slaves. A military critic, writing from the Potomac and the lower counties of Maryland, is urging the application of the same policy to that region, as a means of defeating the contemplated passage of the river by the forces of the South. Whether the rumor so announced prove to be literally correct or not, it is hardly possible that the war can continue long, and grow desperate and earnest on any territory where slavery exists, without leading to this result. Tenderness and deference are sentiments which must soon give place to the stern struggle for life between hostile and desperate men. Already the South has not hesitated, in some instances, to muster her slaves into armed regiments, and in all cases to avail herself of their brawny arms as equally valuable assistants in the work of fortification, camp service, and all the other incidents of war. Still further, as a great body of laborers, undisturbed by the war, quietly conducting the general industry at home, and providing the means of sustaining immense armies in the field, the slaves are, in effect, an important auxiliary of the enemy's power. Already the Congress of the United States has passed a law for the confiscation of all property so used, so stringent in its terms that, without much strain of legal ingenuity, it might be made to cover the whole case. The threatened continuance of disaster to Northern arms may at any moment force upon our generals the military necessity of declaring emancipation within a given district or State, and finally, it may be incumbent on the Government to resort to the same policy in reference to the whole South. The contest is one of life and death for the greatest human interests ever brought face to face in hostile array. But a single step is wanting, and we may at any moment be forced over the boundary which hitherto has prevented it from being a conflict avowedly for the utter extinction of the institution of slavery on the North American continent, on the one hand, and for the triumphant establishment of the policy and power of that institution over the whole land on the other.