The letter from Captain E. Jones, signal officer, is dated Camp E. Kirby [Smith], Mississippi River, 5th of September, 1864, in which he reports at least 6,000 or 7,000 troops as having "passed up yesterday," therefore the 4th of September, 1864. If at least 6,000 or 7,000 men passed Camp E. Kirby [Smith] on the 4th of September, and at least 10,000 passed Morganza on the day and night of the 7th of September, I cannot have estimated the enemy's force too largely. The 10,000 are especially reported as having gone to "re-enforce Steele." General Smith estimates the re-enforcements under Mower at 5,000. Thus the information derived from department headquarters is that Steele was re-enforced by at least 22,000 men, excluding Grierson's cavalry; count these at 1,500, and we have 23,500; add General Smith's estimate of Steele's effectives, 10,000, and we have 33,500 total, excluding the enemy's force at Fort Smith. I have information from several sources, deemed by me reliable, that Thayer has been ordered from Fort Smith to Little Rock, and separate information that all but a small garrison, estimated at 1, 5000 men, have left Fort Smith. It is not likely that Thayer would go to Little Rock without some portion of his troops, say 3,000, and this would make Steele's whole force in hand 35,500. If any mistake has been made at department headquarters about the 10,000 men, and that number should be underrated, we shall still have 25,500 effective men. I think, however, that Steele had more than 10,000 men before the arrival of his re-enforcements, and that Grierson's and Mower's numbers are rather underestimated.

I have not yet heard of the seventeen transports of troops which are reported from department headquarters as having passed up on the 27th of September. I will send information of them as soon as received. In the meantime I should like to receive any additional information as to their destination which may have reached department headquarters. I have this day learned, as I consider, with certainty, that eight regiments of infantry and seven of cavalry, say 8,000 men, have gone into Missouri in pursuit of General Price. They marched west of Back River, and must long since have entered Missouri. I have great uneasiness as to the fate of Price and his expedition. It seems beyond a doubt, notwithstanding this, that Steele is preparing an expedition on a large scale. If there be any offensive demonstration in Louisiana at any point please inform me, always without delay, so that I may have all the information to enable me to detect the plans of the enemy. I have just received (a few moments since) the order to send Harrison's brigade to Louisiana, and issued at once the necessary orders, but I had left that brigade at Monticello, Mount Elba, &c. It must first be relieved. For this purpose I have had Major-General Wharton intercepted in progress at Magnolia, and ordered him to cause Colonel Parsons' brigade, now about crossing the Ouachita at Moro Landing, to march back and relieve Colonel Harrison's brigade, with orders to the latter to proceed, on being relieved, to Alexandria. It will be, therefore, some days before Harrison can take up his line of march. I think it more than probable that the enemy will make a demonstration or feint in Louisiana in order to cause troops to be detached from this district, which, for the autumn at least, must be the real field of operations. I think his design is to occupy if possible the Ouachita River in Arkansas, and at Monroe in Louisiana.

I am, general, very respectfully, your obedient servant,

J. B. MAGRUDER,

Major-General, Commanding.