MOBILE, August 5, 1864.

Brigadier- General LIDDELL,

Clinton, La:

Let General Dick Taylor and General Smith know that a large naval force and a large force under Canby, estimated at 10,000, are attacking Mobile.

D. H. MAURY,

Major- General, Commanding.

CLINTON, August 5, 1864.

Major HART,

Trans- Mississippi Department:

Department commander exceedingly anxious to know where General Taylor is. Where the troops are. Communicate in cipher.

ST. JOHN R. LIDDELL.

[Inclosure Numbers 15.]

HEADQUARTERS TRANS- MISSISSIPPI DEPARTMENT,
Alexandria, August 7, 1864.

Lieutenant General R. TAYLOR,

Commanding, &c.:

GENERAL: The importance of expedition in crossing the infantry under your command to the east bank the river must have impressed itself upon you. Lieutenant-Colonel Douglas, chief engineer of the department, informs me that he has now forty- two pontoons ready for use, which can be transported to any point on the Mississippi River which may be selected for the crossing. In a few days he expects the arrival of twelve additional pontoons. These boats will cross twenty men each, exclusive of the oarsmen, and without the additional boats expected you will be enabled to cross between 800 and 900 men at a single crossing. If any good is to result from the crossing of this force it rests in the speedy execution of the movement and in the their rapid transportation to the scene of action. By crossing beef- cattle and carrying breadstuffs and salt in the haversacks of your men you can, though with some privation, traverse the country from the east bank of the Mississippi River to the country where supplies can be obtained. By taking the artillery to pieces and by swimming the horses you many be enabled to cross a sufficient amount of artillery for your column. General Walker is instructed to designate four batteries of light artillery to accompany your column. If no serious interruption is offered you may be enabled also to cross your trains with supplies, but first crossing your men and artillery. If the way should be closed you can push on with beef- cattle and salt. In the dispatches (copies of which were furnished you) General S. D. Lee promised to have supplies collected east of the Mississippi River forth use of your column. It was, moreover, suggested that you should send commissaries in advance across the river. You will therefore make your arrangements for the immediate crossing of the Mississippi with the force which is to operate under your command. You can consult with Lieutenant-Colonel Douglas, the chief engineer of the department, in regard to the point and mode of crossing. He is directed to report to you for that purpose, in the event you desire his services, and under the instructions contained in the dispatches the troops are tao cross under your orders. You will conduct the operation of crossing in person. Major- General Walker,