For many long months I have labored to prepare the Army of the Potomac to play its part in the programme. From the day when I was placed in command of all our armies I have exerted myself to place all the other armies in such a condition that they, too, could perform their allotted duties.

Should it be determined to operate from the Lower Chesapeake, the point of landing which promise the most brilliant result is Urbana, on the Lower Rappahannock. This point is easily reached by vessels of heavy draught; it is neither occupied nor observed by the enemy; it is but one march from West Point, the key of that region, and thence but two marches to Richmond. A rapid movement from Urbana would probably cut off Magruder in the Peninsula, and enable us to occupy Richmond before it could be strongly re-enforced. Should we fail in that, we could, with the co-operation of the Navy, cross the James and throw ourselves in the rear of Richmond, thus forcing the enemy in come out and attack us, for his position would be untenable with us on the southern bank of the river. Should circumstances render it not advisable to land at Urbana, we can use Mob Jack Bay; or, the worst coming to the worst, we can take Fort Monroe as a base, and operate with complete security, although with less celerity and brilliancy of results, up the Peninsula.

To reach whatever point may be selected as a base a large amount of cheap water transportation must be collected, consisting mainly of canal-boats, barges, wood boats, schooners, &c., towed by small steamers, all of a very different character from those required for all previous expeditions. This can certainly be accomplished within thirty days from the time the order is given. I propose, as the best possible plan that can, in my judgment, be adopted, to select Urbana as a landing place for the first detachments; to transport by water four divisions of infantry with their batteries, the regular infantry, a few wagons, one bridge train, and a few squadrons of cavalry, making the vicinity of Hooker's position the place of embarkation for as many as possible; to move the regular cavalry and reserve artillery, the remaining bridge trains and wagons, to a point somewhere near Cape Lookout; then ferry them over the river by means of North River ferry-boats, march them over to the Rappahannock (covering the movement by an infantry force near Heathsville) and to cross the Rappahannock in a similar way. The expense and difficulty of the movement will then be very much diminished (a saving of transportation of about 10,000 horses), and the result none the less certain.

The concentration of the cavalry, &c., on the lower counties of Maryland can be effected without exciting suspicion, and the movement made without delay from that cause.

This movement, if adopted, will not at all expose the city of Washington to danger..

The total force to the thrown upon the new line would be, according to circumstances, from 110,000 to 140,000. I hope to use the latter number by bringing fresh troops into Washington, and still leaving it quite safe. I fully realize that in all projects offered time will probably be the most valuable consideration. It is my decided opinion that, in that point of view, the second plan should be adopted. It is possible, nay, highly probable, that the weather and state of the roads may be such as to delay the direct movement from Washington, with its unsatisfactory results and great risks, far beyond the time required to complete the second plan. In the first case we can fix no definite time for an advance. The roads have gone from bad to worse. Nothing like their present condition was ever known here before; they are impassable at present. We are entirely at the mercy of the weather. It is by no means certain that we can beat them at Manassas. On the other line I regard success as certain by all the causes of war. We demoralize the enemy by forcing him to abandon his prepared position for one which we have chosen, in which all is in our favor, and where success must produce immense results.

My judgment as a general is clearly in favor of this project. Nothing is certain in war, but all the chances are in favor of this movement. So much am I in favor of the southern line of operations, that I would prefer the move from Fortress Monroe as a base as a certain though less brilliant movement than that from Urbana to an attack upon Manassas.

I know that his excellency the President, you, and I all agree in our wishes, and that these wishes are to bring this war to a close as promptly as the means in our possession will permit. I believe that the mass of the people have entire confidence in us. I am sure of it. Let us then look only to the great result to be accomplished and disregard everything else.

I am, very respectfully, your obedient servant,

GEO. B. McCLELLAN,

Major-General, Commanding.

Honorable E. M. STANTON, Secretary of War.

This letter must have produced some effect upon the mind of the President, since the execution of his order was not required, although it was not revoked as formally as it had been issued. Many verbal.