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

FORT MORGAN.

The construction of traverses has been continued.

FORT GAINES.

The construction of the new wharf has been continued.

FORT POWELL.

The guns on the east face-one 10-inch columbiad, one 7-inch Brooke gun and one 32-pounder rifled, which will be exchanged for one 10- inch columbiad-have been mounted and protected by temporary parapets. The gallery on the south side has been framed and raised. The area of the work has been extended toward the WEST by making a foundation of brick-boats, on which the parapet will be built. The whole work is surrounded by booms; the east and north faces are protected by wooden chevaux-de-frise, but the front being liable to become water-logged, and the latter to destruction by barnacles, an additional row of chevaux-de-frise, made of short piece of railroad iron, of which there was a large quantity taken from Battery Gladden (late Pinto), has been constructed.

TORPEDOES.

The manufacture of Springs' torpedoes has been continued. Forty-six torpedoes of General Rains' pattern have been placed in the main ship channel between Fort Morgan and the WEST bank. We have now 134 torpedoes of Singer's make and 46 of Brigadier-General Rains', three rows and in echelon, placed in the channel. The distance from the water battery to the point at which the three lines of torpedoes commence is 226 yards.

BATTERY M'INTOSH.

Heavy rains necessitated the repair of slight damages. The battery is in good order.

BATTERY GLADDEN.

Five 10-inch columbiads are now mounted. The platforms for the two other guns are ready, and the guns (which are daily expected from Selma) will be mounted on their arrival here. Four of the gun chambers, with their traverses, have been revetted; the fifth is half finished. A blacksmith's shop, much needed in an isolated battery of this class, has been added to the bomb-proof, which has been covered with earth on the south and southwest side. Good progress has been made in the construction of this battery, at which, for the three weeks, two barges of 450 cubic yards capacity each have been employed.

ROUND (LATE IRON-CLAD) BATTERY.

Blacksmiths and carpenters being only needed the battery has been completed for the reception of its guns. See report.

CITY INTRENCHMENTS.

The temporary impressment of 300 negroes from the salt-works has enabled us to make (during the nine days we were allowed to keep them) some little progress.