GREENSVILLE, March 12, 1864.

General S. COOPER:

General Longstreet is temporarily absent. Your dispatch relative to General Law will be laid before him on his return, as it is a matter on which I am incompetent to act in his absence.

S. B. BUCKNER,

Major-General, Commanding.

ATLANTA, March 13, 1864.

Lieutenant-General LONGSTREET:

GENERAL: I met your courier here, where I am on a tour of inspection.

I will obey any orders of the President zealously and execute any plan of campaign of his to the best of my ability. It seems to me, however, that the one suggested to you is impracticable to us, at least at any early day.

In the first place, the enemy could prevent our junction at Madisonville. If I attempt to march directly to tat point they can unite all their forces against me. If to avoid that I diverge into North Carolina, they can unite those forces upon you. If We unite for such an object it should be by our moving into Northwestern georgia to some point in rear of dalton.

In the second place, we must the means of moving from Madisonville with food for man and beast for at least ten days, for the march thence into the productive part of Middle Tennessee and getting the first supplies there would require at least as long. To enable us to do that the Quartermaster's Department must increase the supply train of this army, as well as yours, very much, and the Commissary department furnish the means of loading them. It is a greater undertaking, I think, than anything yet accomplished by those Department, and if they succeed it will not be very soon.

I have orders to prepare for a forward movement, but its precise object has not been imparted to me. It seems to me that we shall be compelled to wait for the grass of May, as we did on the prairies, and besides we ought to let the enemy advance of he will, that we may fight him as far as possible from his base and near to ours. If he will not advance, we must.

I writing to the President on this subject, I expressed the opinion that the only practicable mode of assuming the offensive here seemed to me to be to wait for the enemy's advance, and if we beat him, follow into Middle Tennessee, it being much easier to beat him in Georgia than beyond the Cumberland Mountains and the results of victory much greater. If, as seems probable, Sherman's troops should be brought to Chattanooga, we may have an opportunity to practice this theory. If they come, the union of your army with mine would be necessary.

I regret very much we cannot confer personally. You know how much I value your military opinions.

Most respectfully, your obedient servant,

J. E. JOHNSTON,

General.