Monthly report of operations for the defense of Mobile, Ala., during the month of September, 1864.

ENGINEER OFFICE,

October 6, 1864.

FIRST DIVISION -CITY INTRENCHMENTS.

A. Drains have been repaired and made serviceable.

C. Repairs on traverses damaged by late rains in progress; one formerly repaired during the month.

D. Covering magazine and repairing damages to traverses; magazine nearly completed.

E. Extended flanks and built bastions.

F. Magazine covered and cavalier thereon being built; covered way laid off.

G. Flanks being extended; bastions being built.

Redan between H G being repaired.

I. Flanks being extended.

I to K. Nothing has been done in consequence of continuous rains, but a pump (to be driven by horse-power) has been erected to facilitate the working of this line.

L. No work is now being done on this redoubt, it being ready and finished as far as is now deemed necessary, and redan between L and K is progressing rapidly; curtain connecting this read with L is ready for revetment.

Redan between L and M is nearly finished, and curtain from it to L ready for revetment.

M is finished as far as is designed at present, and ready for its complement of guns.

N is progressing well. The want of lumber has prevented the completion of the magazine and the preparation of the salient gun site, and also delayed the working on the right face of the salient. The rain retarded the building of the sally-port through this face, but the work has nevertheless progressed well. Its flanks have been built, service magazines put in, and six gun-pits made ready on both the right and left faces. The bastions have been partially built but not yet revetted. The curtain line from this work to M is ready for revetment with all the earth taken from the front ditch, and the intermediate redan is in a proper state of progress. Revetting will be commenced as soon as carts for houling sod can be spared. The several redans not especially mentioned are all ready for use and the curtain lines all ready for defense, though from H to I and from D to E the revetment is not yet up.

Battery Buchanan had been completed, but the heavy rain so damaged the traverses as to render a great deal of work in repairs necessary.

Mortar Battery completed.

Missouri Battery has been completed.

SECOND DIVISION -BAY BATTERIES AND OBSTRUCTIONS.

Battery Gladden. -Boomb-proof has been completed, sodded, and a 7- inch Brooke gun has been mounted. A passage of twelve inches was raised from the bottom back of the bomb-proof by sheath piling and a filling of bricks and sand, terre-plein leveled, and battery completed. A wharf ten feet wide, extending FIFTY feet beyond the scarp of parapet, is being built. Breakwater piling driven.

Battery McIntosh. -One gun has been mounted on the east flank and an extension prepared for another. The platform is now ready for a