The sand bank off Dauphin Island extends south as well as east, reaching between four and five miles from the entrance. A similar shoal stretches out to the southward from Mobile Point. Between the two lies the main ship channel, varying in width from seven hundred and fifty yards, three miles outside, to two thousand, or about a sea mile, abreast Fort Morgan. Nearly twenty-one feet can be carried over the bar; and after passing Fort Morgan the channel spreads, forming a hole or pocket of irregular contour, about four miles deep by two wide, in which the depth is from twenty to twenty-four feet. Beyond this hole, on either side the bay and toward the city, the water shoals gradually but considerably, and the heavier of Farragut's ships could not act outside of its limits. The Confederate ironclad Tennessee, on the contrary, drawing but fourteen feet, had a more extensive field of operations open to her, and, from the gradual diminution of the soundings, was able to take her position at a distance where the most formidable of her opponents could neither follow her nor penetrate her sides with their shot. Between the city and the lower bay there were extensive flats, over which not even the fourteen feet of the Tennessee could be taken; and these in one part, called Dog River Bar, shoaled to as little as nine feet. To bring the Tennessee into action for the defense of the entrance and of the lower bay, it was necessary to carry her across these flats--an undertaking requiring both time and mechanical appliances, neither of which would be available if an enemy were inside to molest the operations. As the Tennessee was distinctly the most formidable element in the dangers Farragut had to encounter, and as the character of the soundings gave her a field of action peculiarly suited to utilize her especial powers, which consisted in the strength of her sides and the long range of her heavy rifled guns, it was particularly desirable to anticipate her crossing the upper bar by the fleet itself crossing the lower. That done, the Tennessee was reduced to impotence. It was not done, for two reasons. First, the Navy Department did not send the ironclads which Farragut demanded; and second, the army in the Southwest, having wasted its strength in a divergent operation, was unable to supply the force necessary to reduce Fort Morgan. That the delay was not productive of more serious consequences was due to the impatience or recklessness of the Confederate admiral, and to the energy with which Farragut seized the opportunity afforded by his mistake.