MOBILE, August 19, 1864.

(Received 20th.)

Honorable J. A. SEDDON:

Three thousand small-arms, with ammunition, required immediately for MISSISSIPPI State troops; every source has now been exhausted. Two thousand enfields are still within limits of Mississippi, en route to Arkansas; may I take them? Delay will lose us the State troops.

D. H. MAURY,

Major-General.

ENGINEER OFFICE, DISTRICT OF THE GULF,

Mobile, Ala., August 19, 1864.

Captain GEORGE W. HARRISON,

Commanding C. S. S. Morgan:

CAPTAIN: Your note urging the more efficient obstructions of Blakely and Apalachee Rivers has just been received. In answer, I beg leave to state that I fully share your opinion. In fact, I am so thoroughly convinced of all you say that I am bending all energy toward strengthening the one weak point in our defenses. From the amount of labor done by the engineers during the course of last week you will easily be convinced of the earnestness of our desire to render the tow channels impracticable to any enemy, however active or energetic and enterprising he may be. I have pointed out repeatedly Batteries Huger and treaty as unreliable, yet my frequent and urgent appeals for labor have never been heeded. But let us use the short respite the enemy may grant us to the best possible advantage, and above all let us adopt the view that vessels drawing eight and nine feet can pass the bar. I am much afraid of not being able to render the two batteries what they ought to be. They are faulty in location, in conception, and in construction. It is not possible to alter them now materially, yet I expect much good service from the considerable increase of heavy armament we have been able to give them of late. They can and will make an obstinate resistance, and I do not think that any of the enemy's vessels will live long under their fire. Our object then must be to keep the enemy under one. Our present obstructions will not do it, and they do need immediate strengthening. Rafts or booms would require very substantial piers on either bank of the river. A great objection tot hem is the accumulation of driftwood above them, the length of time they require for their construction, and the difficulty they present in being anchored. I have, therefore, adopted the same plan which was proposed for the obstruction of the channel, between Fort Morgan and the WEST bank, and we two rivers, as there is but one current, less depth of water, better bottom, and no seaway. The top of these sawyers of chevaux- de-frise will be strengthened by an iron cap, on which a torpedo may be fastened. Lieutenant Barrett leaves here to-night with twenty-two torpedoes. I think it would be well to place them just opposite Battery Huger, in the Blakely River, a few yards below the piling, leaving only a narrow channel for our communication by small boats with Bay Minette. A party of FIFTY axmen will leave to- night. Any assistance you may deem proper to give to us hard-pushed engineers will be thankfully reciprocated.

I remain, captain, very respectfully and truly, yours,

V. SHELIHA,

Lieutenant-Colonel and Chief Engineer.