By that time the defences of Mobile were well nigh impregnable.  Fort Gaines, on Dauphin Island, had a garrison of 864 men and mounted three 10-inch columbiads, four 32-pounder rifled guns and twenty smoothbore guns of 32, 24 and 18-pound calibres.  The principal pass to Mississippi Sound was commanded by Fort Powell, with one mounted 10-inch gun, one 8-inch columbiad and four rifled guns.  The main fortification was Fort Morgan, whose heavy guns were placed in three tiers.  It mounted seven 10-inch, three 8-inch and twenty-two 32-pounder smoothbore guns and two 8-inch, two 6.5-inch and four 5.82-inch rifled guns.  The exterior batteries were also heavily armed and the garrison numbered 640 men.  The bay was filled with skilfully placed torpedoes, some of them of stupendous size and power and sufficient, it would seem, if properly handled, to destroy all the navies of the world.

All arrangements being completed, the signal for the advance was hoisted at daylight, August 5, 1864.  The Union fleet consisted of 21 wooden vessels and 6 ironclads.  The wooden vessels sailed in pairs, the larger on the starboard, so that if either was disabled the other could carry it along.  Farragut’s intention was to lead with the flagship Hartford, but he reluctantly allowed the Brooklyn to take that post, since she carried four chase guns to the Hartford’s one and was provided with an ingenious apparatus for picking up torpedoes.  It was contended further that the flagship would be the special target of the enemy, a fact that was likely to cripple her and prevent the employment of the all-important signals.  The last argument bore no weight with Farragut, who replied that she would be the chief target anyway, no matter what the position, and exposure to fire was one of the penalties of rank in the navy.  The monitors were to advance in single file, slightly in advance of the wooden ships, the Tecumseh, Commander Tunis A.M.  Craven, in the lead.

[Illustration:  IN MOBILE BAY.]

In this order the slow advance was begun and at a few minutes past seven the Tecumseh fired the first gun.  The forts waited twenty minutes when they replied, and the Brooklyn responded with two 100-pounder Parrot rifles.  Under the protection of Fort Morgan nestled the Confederate rams and ironclads, which directed their fire principally at the wooden vessels.  The great battle was opened.

The enemy’s gunboats and the ram Tennessee moved out from behind the fort and continued firing at the wooden boats, giving principal attention, as was expected, to the flagship, which was struck several times.  She soon began returning the fire, still advancing, and repeatedly drove the gunners from the water batteries, but they immediately returned and kept bravely at work.